Cataract Surgery, 3rd Edition

PART V – Special Techniques for Cataract Extraction

Chapter 26 – Surgical Management of Pediatric Cataracts and Aphakia

Howard V. Gimbel, MD, MPH,
Brian M. DeBroff, MD,
Jennifer A. Dunbar, MD,
Bharti R. Nihalani, MD


Contents

  

   

Etiology of Congenital Cataract

  

   

Preoperative Evaluation

  

   

Timing of Surgery

  

   

Are Pediatric Eyes Different?

  

   

Review of Pediatric Surgical Techniques

  

   

Current Surgical Techniques

  

   

Postoperative Treatment

  

   

Complications of Pediatric Surgery

  

   

Glaucoma

  

   

Challenges

  

   

Conclusions

CHAPTER HIGHLIGHTS

  

   

Capsule and zonule differences from adult lens require different techniques

  

   

Management of inflammation and reactive membranes

  

   

Intraocular lens (IOL) power calculation and strategies in growing eyes

  

   

Secondary IOL implantation in children

Pediatric cataract is one of the leading causes of treatable childhood blindness, accounting for 7–20% of blindness in children worldwide.[1,][2] A prospective collaborative project conducted by 12 US universities reported the prevalence of infantile cataract as 13.6/10,000 infants.[3] In 2003, Holmes et al. reported, in a retrospective population-based medical record retrieval in the US population, that the birth prevalence of visually significant cataracts was 3.0 to 4.5 /10,000.[4]

Because of the high incidence and treatable nature of the condition, an improved approach to the management of childhood cataracts would have a large impact on childhood blindness as a whole.

Cataract extraction with lens implantation in children has undergone dramatic changes during the past 40 years, largely as a result of advances in technology and microsurgical techniques.[5–11] Managing cataracts in children remains a challenge; treatment is often difficult and tedious and requires a dedicated team effort. The timing of surgery, the surgical technique, the choice of the intraocular lens (IOL), and the management of amblyopia are of the utmost importance for achieving good visual results in children.[7,][12–15] Other challenges in the management of cataracts in infants and children include the difficulties in examining this particular group, the risks of general anesthesia, poor preoperative pupillary dilation, and the management of postoperative inflammation and fibrin formation. Children are at higher risk for postoperative pupillary capture, posterior synechiae, IOL precipitates, fibrinous uveitis, corectopia, pupillary block glaucoma, and peripheral iris erosion.[16] Many ophthalmologists lack surgical experience of this particular group of patients. The development of continuous curvilinear capsulorrhexis (CCC)[17] and viscoelastic agents, advances in posterior chamber IOL designs, and the use of the neodymium:yttrium-aluminum-garnet (Nd:YAG) laser have brought the pediatric cataract surgical technique closer to the adult procedure. With advancements in surgical techniques, improved intraocular lenses and better understanding of the growth of the pediatric eyes, primary implantation of intraocular lenses is becoming popular even in the youngest of patients.

There are many nuances of pediatric surgery – including preoperative evaluation, timing of surgery, operative technique, and postoperative management – which this chapter will attempt to elucidate. The evolution of techniques in pediatric cataract surgery will be emphasized, including the trend toward anterior and posterior CCC, anterior vitrectomy, placement of posterior chamber lenses in the capsular bag, and methods to reduce the formation of secondary cataracts.

Etiology of congenital cataract

The most common cause of bilateral congenital cataract is idiopathic. About one-third of cases are hereditary, without a systemic disease. Other causes include metabolic disorders, intrauterine infections, systemic abnormalities and a few ocular conditions. In contrast, unilateral cataract in most cases is idiopathic.[18]

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Preoperative evaluation

A preoperative assessment is essential to adequately evaluate the size, density, location, and visual impact of the cataract; to evaluate for other ocular abnormalities; and to properly plan the surgical procedure. A history from the parents is often helpful in clarifying whether the cataract is congenital, developmental, or traumatic, and to ascertain if there was any maternal drug use, infections, or exposure to ionizing radiation during pregnancy. Infants with bilateral congenital cataracts demonstrate decreased visual interest and may have delayed developmental milestones.[19] Past or present illness and a history of medication use may give a clue as to the cause of the cataract. Past ocular history and a family history of ocular diseases may reveal other possible causes.

The value of counseling the parents cannot be overstressed. Parents should understand that treatment of the child continues well after surgery. They need to come for regular follow-up visits and help ensure that the child wears glasses or contact lenses despite IOL implantation; the child may also need occlusion therapy following surgery. In addition, further interventions such as a secondary procedure to clear the visual axis or strabismus surgery may be required.

Complete examination of infants and young children with fully dilated pupils, done, if necessary, under sedation or even general anesthesia, is mandatory in both the eyes. Although there may be variations in the baseline ophthalmic assessment because of the age and compliance of the pediatric cataract surgery patient, a full anterior and posterior segment examination is essential in all patients preoperatively. An assessment of the best corrected visual function is performed by testing the patient's ability to fix and follow (in infants), progressing to picture cards, illiterate Es, and Snellen letter charts in older children. Cycloplegic refraction by retinoscopy, autorefractor, or even trial lenses is important to determine the best correction. Binocularity, fusion, and stereopsis testing preoperatively give the ophthalmologist an idea of how well the eyes function together. Strabismus evaluation should involve cover–uncover and alternative cover testing for both distance and close up. Any restrictions of extraocular movements should be noted. The presence of nystagmus is an ominous sign, indicating poor vision resulting from sensory deprivation.[20] Pupils should be evaluated for the presence of an afferent pupillary defect.

An anterior segment examination, preferably by slit-lamp microscopy, may reveal potential challenges to surgery, including iris deformities, synechia, zonulolysis, posterior lentiglobus, intumescent cataract, pre-existing posterior capsule defect, anterior or posterior capsule plaques, or evidence of past trauma. The extent and location of the cataract must be evaluated. Small anterior polar cataracts often do not require lens extraction, whereas nuclear and, especially, posterior opacities tend to be more visually significant.

When the clarity of the media permits, indirect ophthalmoscopy will reveal any posterior segment abnormalities or pathologic condition that may have an impact on postoperative vision. Axial length and corneal curvature are essential measurement for IOL power determination. To measure the axial length of an eye in a child as young as 2 years old, a hand-held A-scan and keratometry can be performed without sedation so that the child can fixate on a target object. However, both A-scan and keratometry may be performed in the operating room under general anesthesia prior to cataract extraction or during an examination under anesthesia. In the event of a traumatic cataract in which the A-scan is unattainable, the patient's other eye may be used for proxy measurements on which to base IOL power calculations. Corneal diameter measurement helps rule out microcornea. Measurement of intraocular pressure can be accomplished by Tonopen, Shiotz tonometry, or pneumotonometry under anesthesia in infants or by applanation tonometry in older children. If the cataract is very dense with no view of the fundus, a B-scan will help evaluate any posterior segment abnormalities. Also, electrophysiological testing, including electroretinography and visual-evoked potential, may be performed to assess the neurological function of the retina and to detect stimulus deprivation and amblyopia.[21]

Consultation with a pediatrician is essential for infants with congenital cataracts. Some laboratory tests that may be considered include urine evaluation for reducing substances; toxoplasmosis, rubella, cytomegalovirus, and herpes simplex titer; serum screen for galactosemia; and a serum calcium screen to evaluate for hypoparathyroidism.[22] Also, it is important to observe for any systemic processes that may be coexistent, especially in children with bilateral cataracts. Genetic testing should be considered for infants with congenital cataracts.[23]

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Timing of surgery

The timing for surgical intervention in pediatric cataracts was profoundly influenced by the work of Hubel and Weisel and later by von Noorden who established that sensory deprivation in the first few months of life is the critical period for visual development and that sensory deprivation during this period results in both irreversible anatomical changes in the lateral geniculate bodies and decreased activity in the occipital cortex upon visual stimulation.[13,][23,][24] Congenital monocular complete cataracts should be removed within the first few months of life and, preferably, in the first few days or weeks of life.[25–27] If surgery is performed within the first 4 months of life, deprivation amblyopia can still be reversed.[14,][22,][28] Bilateral complete congenital cataracts should be removed within the first few months of life, first in the eye with the more opaque lens opacity and approximately 1 week later in the other eye. In children who are at an age at which they are at risk for the development of amblyopia, a monocular cataract should be operated on when the best corrected visual acuity is 20/70 or worse.[29] Recommendation for surgery in children with bilateral cataracts is often made when the vision in the worse eye is 20/70 or poorer. In children older than 8 years, who are no longer at much risk for amblyopia, cataract surgery is recommended when the child has difficulty functioning in school or in sports, or has problems with normal daily activities. Indications for cataract surgery include visually significant central cataracts larger than 3mm in diameter, dense nuclear cataracts, cataracts obstructing the examiner's view of the fundus and cataracts associated with strabismus. Certain cataracts like anterior polar, sutural, lamellar or blue dot cataracts may be compatible with good vision and may be followed up to watch for any progress. Although surgical removal is the definitive therapy for the vast majority of congenital cataracts when visual function is jeopardized, visual acuity in many children with small cataracts may be improved by first maintaining dilation of the pupil. When cycloplegia is used, however, photophobia is often aggravated and reading glasses are often necessary.[20,][30]

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Are pediatric eyes different?

In comparison with adult eyes, pediatric eyes have greater elasticity of the capsule, lower scleral rigidity and more mitotically active lens epithelial cells, leading to higher incidence of posterior capsule opacification necessitating primary management of the posterior capsule. They also have a thick vitreous gel which may give more protection against cystoid macular edema.

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Review of pediatric surgical techniques

The early years

Several different surgical techniques for the management of cataracts in pediatric patients have been advocated in the past, including discission or needling, linear extraction, or a combination of discission and displacement of lens fragments into the anterior chamber by irrigation without IOL implantation.[31–34] In the early 1960s the aspiration procedure, as popularized by Scheie and associates,[35] with the widespread use of the operating microscope became the accepted technique for extracting cataracts in infants and children.[35,][36]With the aspiration technique, the lens material was suctioned by a push–pull technique using a needle with a syringe attached. Using this method, surgical complications associated with earlier techniques were dramatically reduced. Significant intraoperative risks, however, such as anterior chamber collapse and vitreous loss remained prevalent.[35,][36] The Scheie technique, which leaves the posterior capsule intact, led to an extremely high incidence of secondary membranes and the development of synechiae between the iris and the remaining capsular bag. A sector iridectomy was necessary to prevent iris bombé and secondary glaucoma.[31,][35,][37–40] Often, additional operations using general anesthesia were required. The delay in amblyopia therapy became significant and was undoubtedly part of the poor visual results seen in patients with unilateral and bilateral congenital cataracts.

In the mid-1960s, the next development that changed pediatric cataract surgery was the introduction of a double-barreled cannula, one for aspiration and one for irrigation.[41] The irrigation–aspiration technique enabled the ophthalmologist to maintain anterior chamber depth during cataract aspiration while keeping the posterior capsule intact. Unfortunately, in many pediatric cases, residual lens epithelial cells would still relentlessly grow in from the periphery and cover the posterior capsule surface, resulting in an opaque membrane.[37] The incidence of postoperative secondary membrane formation with aspiration techniques remained high,[37,][42] necessitating a secondary surgical procedure weeks or months later to open the posterior lens capsule.[43]

The 1970s witnessed the introduction of phacoemulsification in pediatric cataract surgery.[44,][45] Although many pediatric cataracts can be removed using the irrigation–aspiration handpiece alone or by using the phacoemulsification handpiece with no ultrasound power, in some cases short bursts of phacoemulsification may be required. Pediatric cataracts vary dramatically in type, ranging from the very soft to the very hard and calcified. Nuclei that are too hard to be simply aspirated can be fragmented using phacoemulsification. Thus, phacoemulsification in pediatric surgery allows a wider application of the basic aspiration technique.[46,][47] In addition, the closed phacoemulsification system incorporates the principles of controlled infusion to maintain intraocular pressure and variable and controlled suction or aspiration. Even with phacoemulsification and meticulous polishing of the anterior and posterior capsule, however, the incidence of posterior capsule opacification remained significantly high.[48–50]

Pediatric intraocular lens implantation

The options for optical correction following congenital cataract surgery are primary intraocular lens implantation, aphakic glasses, contact lenses and secondary intraocular lens implantation.

Aphakic spectacles are severely debilitating visually, cosmetically, and psychologically. Contact lenses have proved to be a good option. Contact lenses also provide an answer to the problem of the changing refraction that often accompanies IOL implantation in children. However, contact lenses are successful in a relatively small number of pediatric cases over a long period, are emotionally stressful both for the child and the family, and are economically beyond the reach of many patients, particularly those in developing countries.[51,][52]Epikeratophakia is no longer practiced in pediatric eyes. It requires intensive postoperative management and may be associated with decreased corneal lenticular clarity, irregular astigmatism, spherical error, and a prolonged period until visual rehabilitation is achieved.[53–55] Such difficulties with aphakic spectacles, contact lenses and epikeratophakia, combined with more experience with IOLs, viscoelastics, improved IOL design, and improved surgical techniques, have increased the popularity and diminished the controversy over IOL implantation. Pseudophakia offers the method of optical correction that requires the least compliance and induces minimal aniseikonia and astigmatism.[56]

Intraocular lens implants were first advocated by anterior segment surgeons as early as 1955.[5,][57–60] Early IOL implantation in children involved anterior chamber and iris-supported IOLs.[59] The first published implantation of an IOL in a child was by Choyce in 1955, using an anterior chamber lens.[61] Anterior chamber lenses may stimulate an inflammatory response as a result of their contact with vascular tissues and are associated with long-term complications in adults.[6,][62] Endothelial cell loss over many years is a concern, especially with children who tend to rub their eyes frequently. Trauma to an eye with an anterior chamber lens may lead to iris or ciliary body rupture. Binkhorst and Gobin implanted an iridocapsular fixated IOL in 1959 (Figure 26-1).[63] When fixed and stable in the capsule, the iridocapsular IOLs were very successful. Some, however, were associated with complications, including iris sphincter erosion, hyphema, anterior synechiae, iris bombé, iritis, and pupillary fibrotic membranes. Also, lens dislocation, pseudophakodonesis, and corneal endothelial trauma were possible when capsule fixation was not achieved.

  

 

Figure 26-1  Capsule-fixated Binkhorst two-loop iridocapsular lens.

 

 

These complications, which were secondary to inferior lens design and primitive microsurgical techniques, had at one point made IOL implantation in children a very controversial subject. Additional negative opinion toward implantation of IOLs in children resulted from the concern of the possible long-term risk of the eye reacting to polymethylmethacrylate. The observation times in most pediatric IOL series are short in relation to a child's life expectancy.[5,][9,][52,][64–68] Also, many ophthalmologists were concerned that an intense inflammatory reaction might be incited by placement of implants in infants. Histopathological studies, however, have subsequently revealed that the eyes of children could tolerate IOLs in a manner similar to that of adult eyes.[69] Work by Hiles in the 1970s and 1980s helped demonstrate the safety and effectiveness of aphakic rehabilitation of children with IOLs, especially in cases of traumatic or unilateral infantile cataracts.[6,][70]

Intraocular lens implantation is now becoming the preferred method of pediatric aphakic rehabilitation, especially for children over 1 year of age.[6,][26,][49,][52,][56,][58,][71–77] With IOL implantation, there is almost immediate postoperative visual rehabilitation, which maximizes the treatment of amblyopia. In addition, the technique of CCC developed in the 1980s providing assurance of in-the-bag placement of the IOL, and the development of improved lens designs, have helped avoid many complications associated with early lens implantation in children. Relative contraindications do exist for IOL implantation. They include glaucoma, persistent or recurrent uveitis, aniridia, severe microphthalmia, persistent hyperplastic primary vitreous, other ophthalmic defects that preclude useful vision, and cases of inadequate capsular support.[6] Recent studies have shown that good results can be achieved in microphthalmic eyes, and this problem is now becoming less of a concern.[78,][79] Capsular tension rings with artificial irides may provide improved quality of vision in patients with aniridia.

Some ophthalmologists consider patient age of less than 1 year to be a relative contraindication for IOL implantation. The youngest age at which implants can be safely and effectively used has not yet been clearly established. Many ophthalmologists prefer aphakia for bilateral congenital cataracts with the plan of secondary implants within a couple of years. In children older than 2 years of age, lens implantation into the capsular bag may be routinely achieved in monocular or bilateral congenital, developmental, or traumatic cases using current surgical techniques, including continuous curvilinear capsulorrhexis, and viscoelastic materials. Experts in the field of infantile cataract extraction have recently been implanting posterior chamber IOLs in infants as early as 2 months old.[80,][81] Proponents of IOL implantation for treatment of unilateral infantile aphakia claim that this is the best available method to reduce the incidence of irreversible amblyopia.[80–82] Recent studies have shown the effectiveness of bilateral implants in children over the age of 2,[83] and other studies have demonstrated excellent results in children between the ages of 4–6 months of age.[84] More recently, O'Keefe et al found bilateral IOL implantation safe and produced good visual results in children of all ages including infants.[85] Peterseim and Wilson have also published encouraging results.[86] Because the infant eye has a rapidly changing refraction during the first year of life, controversy surrounds the correct choice of lens power for implants in infants.[81]

The development of the eye necessitates initial under-correction to avoid permanent over-correction. The growth of the anterior segment of the eye is generally completed at the end of the second year of life.[87] Therefore, little adaptation of the size and power of the IOL is needed in the eyes of children older than 2 years. Under power of the IOL targeting hyperopia is often desired in younger children, although anisometropia should be minimized to promote binocular function. The final hyperopia desired should be correlated to the child's age. Because the greatest change in axial length and keratometry readings occurs in the first 2 years of life, it is wiser to choose an IOL that will initially correct only 80% of the aphakia in infants. In order to minimize the need to exchange IOLs, it is preferable to under-correct young children by 10 to 20%. In infants, greater degrees of initial hypermetropia are required because the greatest degree of eye growth occurs before 2 years of age. Over 6diopters (D) of average myopic shift has been documented in pseudophakic infants over a minimum 2-year follow-up.[88] Aiming for emmetropia in infants would create a large myopic shift that can be amblyogenic itself and may require an IOL exchange, or piggyback IOL such as an implantable corrective lens (ICL) or corneal refractive surgery, when age permits.[89,][90] An infant should receive 80% of the IOL power needed for emmetropia.[88] The initial hypermetropia can be corrected with spectacles or contact lenses and adjusted as the eye grows, to prevent amblyopia. Dr. M. Edward Wilson has developed a technique of piggyback IOL for infants with a planned removal of an IOL later in life after eye growth.[91] The permanent IOL is placed within the capsular bag and the temporary IOL is placed within the ciliary sulcus. On average a 26.5D IOL is placed in the bag and an 11D lens in the sulcus. In the future ICL lenses may be considered for this technique. This approach may be most appropriate for families less likely to comply with scheduled follow-up visits or wearing glasses full time. In children aged 2–5 years, a postoperative hyperopic spherical equivalent of 2.5D is desired. Preschoolers are usually able to tolerate small amounts of residual hyperopia and astigmatism quite well without the need for spectacle correction. Higher residual refractive errors can be corrected with glasses, which are adjusted as necessary during childhood. Using this method, the patients are initially hyperopic. As the eye grows, emmetropia is approached, and by adolescence moderate myopia is common. Eye growth with progressively decreasing hyperopia appears to run its normal course in the eye with an IOL provided that the eye attains sufficient visual acuity.[87,][92] In children who have already started school, the desired postoperative refraction should approach emmetropia. Bifocal lenses are often required for near vision.

Compared to the other currently available methods, postoperative amblyopic therapy is best maximized by the immediate visual rehabilitation afforded by IOL implantation.[49,][50,][93]Better visual outcomes in children with IOLs are probably related to the uninterrupted and permanent optical correction provided by the lens implant. Strict compliance with amblyopictreatment, however, is still necessary.[94] It is undeniable that in young children in need of amblyopic treatment, implantation of IOLs has far-reaching advantages, including immediate correction of the major portion of the refractive error. IOL implantation with patching of the nonoperated eye is most readily accepted by children and parents, and it maximizes postoperative visual acuity.[51]

Primary implantation of an IOL after cataract removal is gaining popularity, even in infants and young children.[95] A large randomized clinical trial, the Infant Aphakia Treatment Study (IATS), is currently underway to compare primary IOL implantation with contact-lens correction in children undergoing unilateral cataract surgery in the first year of life. A current trend among high-volume cataract surgeons dealing with pediatric cataracts and many pediatric ophthalmologists is to consider IOL implantation as a viable option on a selective basis in children who are under 2 years.

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Current surgical techniques

In cataract surgery on a child's eye the surgeon should strictly adhere to the principles of the closed-chamber technique, such as valvular incision, injection of viscoelastic before removing any coaxial instrument from the eye, bimanual irrigation–aspiration, and two port anterior vitrectomy.

Pars plana vs. limbal approach

In addition to successfully managing secondary membranes and vitreous loss, vitrectomy instruments have allowed surgeons to perform cataract procedures via a pars plana approach.[96–98] Both the limbal and pars plana approaches have their advocates and opponents.[51,][94,][99,][100] The main advantages of the pars plana approach are the reduced incidence of vitreous prolapse into the wound and retinal traction when performing an anterior vitrectomy,[101] the facilitation of reaching lenticular material in the periphery, and less damage to corneal endothelium and iris tissue.[99,][102] The principal disadvantage of the pars plana approach is the loss of integrity of the capsular bag. Removal of the entire cataract by a pars plana approach takes away the majority of capsular bag support for IOL placement and virtually eliminates the possibility of in-the-bag IOL placement.[99,][53] Implantation of a posterior chamber lens in the sulcus, although possible after pars plana lensectomy, is less certain and advantageous.[103] An IOL placed in the sulcus has the disadvantage of contact with vascular tissue and the possibility of inducing a chronic inflammatory response. Thus, the pars plana approach limits the safety of IOL placement and decreases the options for optical rehabilitation if contact lenses cannot be worn or if epikeratophakia fails. The pars plana approach also increases the risk for iatrogenic retinal dialysis or ciliary body detachment.[96] Perhaps the only true indication of pars plana lensectomy is a small eye with microcornea, microphthalmos, or small pupil.

The risk of retinal detachment, however, has persuaded many ophthalmologists to use the limbal approach.[104] Keech et al. report one case of retinal detachment 6 years after translimbal lensectomy and anterior vitrectomy.[104] Studies, however, have shown no statistically significant differences between the limbal and pars plana approach.[105] Increasing preference for the limbal surgical approach for pediatric cataract extraction also occurred with the introduction of higher viscosity viscoelastic agents including Healon GV and Healon 5. These agents have facilitated the maintenance of the anterior chamber, the performance of anterior and posterior capsulotomies, the manipulation of instruments within the anterior chamber, and the placement of IOLs into the capsular bag, while protecting the corneal endothelium.[18] The limbal approach allows CCC, complete removal of the cataract, PCCC, optic capture and or anterior vitrectomy and implantation of an IOL in the capsular bag. As pediatric surgical techniques and intraocular implants have continued to be refined, more interest has shifted to posterior chamber IOLs placed through a limbal incision into the capsular bag as a means of aphakic correction in children of younger ages and even infants.

Some surgeons prefer a combined approach using a limbal approach for performing an anterior CCC and implantation of IOL in the bag and subsequently perform posterior capsulotomy and anterior vitrectomy using parsplana incision.

Paracentesis Incision

A paracentesis incision should be created in the clear cornea 30° on either side of the main incision. Some surgeons prefer two paracentesis incisions, for instance at 12 and 6 o' clock if the main incision is made temporally. The anterior chamber should be inflated with a high-viscosity viscoelastic agent before creating the main entry. The small tunnel paracentesis incisions of 0.9–1.2mm width are adequate to allow insertion of irrigation–aspiration cannulas and vitrectomy probe. Bimanual irrigation–aspiration is preferred in pediatric cataract surgery because it maintains a stable anterior chamber and allows thorough removal of cortical material, which helps to reduce the incidence of postoperative inflammation and secondary cataract formation. Since there is a tendency in the pediatric population for the paracentesis to leak, some surgeons attempt to eliminate their use, or make them with a longer tunnel length to prevent leakage. The paracentesis incisions may be helpful in breaking the anterior synechiae and for assisting in the placement of an IOL. A paracentesis is also helpful to re-form the anterior chamber and obtain and test the seal of the main incision.

Limbal Incision

A 2.6–3mm wide limbal valvular incision with 1–1.5mm internal entry is preferred. Some surgeons prefer to place the incision in the steep meridian obtained by keratometry. The sclera in a young child is elastic, encouraging the use of the smallest possible incision, which also helps to prevent iris prolapse. For a scleral tunnel incision, a small scleral scratch incision is made approximately 2mm from the limbus and is dissected as a 3mm or 5.5–6.5mm wide scleral tunnel depending on the IOL selected using a crescent blade (Figure 26-2).

  

 

Figure 26-2  Scleral tunnel incision (cross-sectional view).

 

 

Capsulorrhexis

Achieving an intact and identifiable continuous capsular rim with the CCC technique is an important step in pediatric implantation procedures because it facilitates lens extraction and assures in-the-bag placement of the IOL. A high-viscosity viscoelastic, preferably Healon GV or Healon 5 is used to counteract the intralenticular forces that cause the CCC's tendency to turn toward the equator. Manual CCC may be achieved using a bent needle, cystotome, forceps, or a combination of these. A forceps is often necessary for control of the elastic capsule encountered in children. Because of the increased elasticity of the pediatric capsule,[106] any discontinuity that occurs in the rim during a capsulotomy can easily extend as a tear out to the equator. When this happens, the edges of the capsule may retract, making it extremely difficult to ascertain, with confidence, that the lens loops are positioned in the capsular bag. Also, anterior capsule tears that extend into the posterior capsule present the greatest intraoperative challenge for nucleus removal, and they compromise in-the-bag or even sulcus IOL placement.

When attempting CCC in a pediatric patient, the tip of an irrigating cystotome, bent needle, or capsulorrhexis forceps is used to make a small central puncture (Figure 26-3). The elastic pediatric lens capsule requires a distinct pressure point to achieve a central puncture. Once the central puncture is made, the cystotome or forceps guides the tear radially out to the desired circumference at the 3 o'clock position (Figure 26-4). If the tear is not easily guided because of the elasticity of the capsule, forceps are more effectively used to grasp at the leading edge of the tear (Figure 26-5). To overcome the stretchability of the capsule, several repeated grasps at the leading edge of the tear are recommended for maximal control of the tear. With these small regrasping maneuvers at the leading edge of the tear, capsulorrhexis is directed to achieve the desired diameter. Viscoelastic material is added as required. The capsulorrhexis should be kept relatively small because the elasticity of the child's lens capsule can create a capsular opening that is larger than expected or desired. The pediatric capsule acts like a thin rubber sheet that retracts toward the periphery after anterior capsulotomy. This elasticity necessitates frequent relaxing and regrasping of the leading edge of the capsular tear with careful observation and direction of vector forces to ensure that radial extensions are prevented. During capsulorrhexis, the internal pressure or anterior chamber depth needs to be well maintained by injecting a viscous viscoelastic agent such as Healon GV or Healon 5. A central capsulorrhexis of about 4.5–5mm is usually adequate so that it covers the IOL optic in all directions.

  

 

Figure 26-3  Cystotome makes a central puncture in anterior capsule.

 

 

  

 

Figure 26-4  Cystotome guiding tear radially to start continuous curvilinear capsulorrhexis.

 

 

  

 

Figure 26-5  Capsulorrhexis forceps is used for better control of progressing curvilinear tear.

 

 

Alternative techniques currently available include vitrectorrhexis, radio-frequency diathermy and Fugo plasma blade. Vitrectorhexis has proved to be a good alternative to manual CCC for young children, especially in the first 2 years of life when the capsule is very elastic and difficult to control. Vitrectorrhexis is easier to perform and is a good option for children when anterior vitrectomy is performed as part of primary management. In contrast, a diathermy-cut capsulotomy, even when performed perfectly, can be seen to have coagulated capsular debris along the edge.[107] In addition, this edge has been shown experimentally to be less elastic than a manual CCC. The Fugo blade is a unique cutting instrument that uses plasma for ablating tissue.[108,][109] The Fugo blade helps to create a perfectly controlled anterior capsulotomy of any size, without the risk of a radial tear. The peculiar structure of the cut edge ensures that even if a deliberate radial cut is made in the capsulotomy, it will not spontaneously extend towards the equator. Radio-frequency diathermy and the Fugo blade are recommended when fibrotic capsules are encountered or in white mature cataracts with the absence of the red reflex, if trypan blue is not available. All these alternative methods may not leave as much of a tear-resistant capsular edge as manual CCC, which is especially important for performing optic capture. Wilson has compared five different anterior capsulotomy techniques using a porcine model.[110] Extensibility and edge characteristics were reviewed with each technique. Manual CCC was found to produce the most extensible capsulotomy with most regular edge.

If the cataract is intumescent, trypan blue is used to stain the capsule, then a sharp needle is used to make the central puncture in the capsule (Figure 26-6), and any liquid cortex is aspirated prior to capsulorrhexis (Figure 26-7). Intumescent cataracts have high intralenticular pressure; hence, the surgeon should always aim for a small capsulorrhexis. The capsulorrhexis can be enlarged using the two-stage CCC technique (initial small and definitive large rhexis just before IOL implantation).[111] If poor visualization prevents a CCC from being performed, a can-opener capsulotomy is best achieved using several small bites with a needle or a cystotome (Figure 26-8). Liquid lens material may then be aspirated using a 25-guage cannula through a paracentesis and a chamber maintainer through another and, if necessary, the remaining nucleus is removed with an irrigation–aspiration or ultrasound hand piece. The can-opener capsulotomy is converted to a CCC using the two-stage CCC technique prior to IOL implantation (Figures 26-9–26-12).[112]

  

 

Figure 26-6  Sharp needle is used to make central puncture in anterior capsule of intumescent lens.

 

 

  

 

Figure 26-7  Liquid cortex is aspirated from capsular bag of intumescent lens.

 

 

  

 

Figure 26-8  Can-opener capsulotomy necessitated by poor visualization in intumescent lens.

 

 

  

 

Figure 26-9  A scissor cut begins the two-stage continuous curvilinear capsulorrhexis technique to convert can-opener capsulotomy to continuous curvilinear capsulorrhexis.

 

 

  

 

Figure 26-10  Forceps continues the conversion.

 

 

  

 

Figure 26-11  Continuous curvilinear capsulorrhexis progresses.

 

 

  

 

Figure 26-12  Two-stage continuous curvilinear capsulorrhexis conversion is completed.

 

 

Irrigation–Aspiration and Ultrasound

Separate irrigation–aspiration minimizes the anterior chamber fluctuations and aids in thorough removal of cortex, which is especially crucial in these small eyes. Most nuclei are too soft to be fractured and the lens removal can be accomplished using bimanual irrigation–aspiration. In rare cases, the harder nuclei may require short bursts of ultrasound energy using the phacoemulsification handpiece.

Posterior Continuous Curvilinear Capsulorrhexis

A planned primary posterior capsule opening, created either in an attempt to prevent inevitable secondary cataract formation or to remove a posterior plaque, should be achieved using the PCCC technique. PCCC can also be used as a method of preventing the extension of a tear when a small linear or triangular posterior capsular rupture inadvertently occurs. Posterior capsulorrhexis requires the use of viscoelastic agents and may be performed before or after posterior chamber IOL in-the-bag implantation.[113] Primary posterior capsulotomy is the preferred choice in children up to 6–8 years of age. Primary capsulotomy is combined with vitrectomy depending on the IOL material and design and the age of the child at surgery.

After aspiration of the lens matter, the capsule bag and the anterior chamber are filled with high-viscosity viscoelastic agent sodium hyaluronate. A 26-gauge cystotome or bent tip of a disposable needle makes the initial puncture (Figure 26-13). For this, the cystotome or needle engages the central capsule, lifts it towards the surgeon and at the same time initiates the puncture. Pushing the margin of the puncture inferiorly creates a small flap. The flap is then held with capsulorrhexis forceps and a PCCC is accomplished aiming at a size of 3.5–4mm by using the ACCC principles and strategies. Additional viscoelastic material can be placed through the central puncture of the posterior capsule to push the vitreous face away (Figure 26-14). Care should be taken that the viscoelastic agent does not push the flap posteriorly, thus making it difficult to grasp the posterior capsule tag. Also, if too much viscoelastic material is pushed through the opening, it may extend the tear in an unpredictable fashion. The end result should be a well-centered PCCC concentric to and smaller than the ACCC. PCCC resists the peripheral extension of the tear and holds the vitreous in place. The IOL can be supported over the capsule. PCCC can also be performed after the placement of an IOL. This ensures IOL fixation in the desired plane. However, performing PCCC and anterior vitrectomy becomes more difficult with this method and may require a pars plana approach. Moreover, manual capsulorrhexis is believed to yield a stronger margin than the vitrector-assisted capsulotomy.

  

 

Figure 26-13  Posterior continuous curvilinear capsulorrhexis is started using a cystotome to create a central puncture of the posterior capsule posterior to the posterior chamber intraocular lens.

 

 

  

 

Figure 26-14  Posterior continuous curvilinear capsulorrhexis (CCC) is extended toward 3 o'clock; this technique is similar to that used with CCC.

 

 

Anterior Vitrectomy

The anterior vitreous is more reactive in infants and young children. Inflammatory response in small children is severe and fibrous membranes may form on an intact vitreous face. This acts as a scaffold for lens epithelial cell (LEC) migration and proliferation. Hence anterior vitrectomy along with posterior capsulotomy is advocated in infants and young children up to 2 years of age.

The aim of vitrectomy is to remove the central anterior vitreous without complete peripheral vitrectomy. For this limited purpose, most surgeons prefer the anterior approach through two limbal (corneal) ports. Removal of subincisional vitreous is accomplished thoroughly by exchanging the ports. The main valvular incision seals itself and maintains the stability of anterior chamber, reducing the fluctuations of iris-lens diaphragm and uveal trauma. The vitrectomy probe is kept steady with the port directed posteriorly within the area of PCCC. A central anterior vitrectomy up to the depth of 2mm is adequate. The recommended parameters are 30cc flow rate, 300–400cc vacuum and 400–800 cut rate.

Intraocular Lens Implantation

IOL fixation, material and size are important determinants of immediate and long-term outcome. In-the-bag fixation is the most preferred site of IOL implantation. Regarding IOL material, polymethyl methacrylate (PMMA) is the material that has undergone the most historical testing and of which surgeons have the most experience. An exaggerated capsular and inflammatory response, however, has remained a problem with PMMA material. Despite meticulous surgical technique, problems like visual axis opacification, inflammatory cell deposits, synechiae and pupil capture are often encountered in the early postoperative period. Moreover, PMMA is a rigid material, which requires an incision as large as the IOL optic diameter for implantation. Kugelberg and co-authors in their animal studies have showed that implantation of a regular-sized PMMA IOL retards eye growth in newborn rabbit eyes. Modification of PMMA surface was advocated to render IOL more biocompatible. Heparin surface modification was found to lower the incidence of inflammatory cell deposit formation. However, it did not alter the capsular behavior. PMMA IOLs are, therefore, gradually losing their popularity.

AcrySof is representative of the group of foldable IOLs made from flexible hydrophobic acrylic material (Alcon Laboratories, Fort Worth, TX). Acrysof is available as either a three-piece or a single-piece lens. The current opinion favors the use of AcrySof IOLs.[95] With AcrySof, the type of PCO is predominantly proliferative. PCO sets in at a later stage, typically at 14–16 months. Visual axis obscuration produced with AcrySof is less severe than PMMA and is, therefore, less amblyogenic. The preliminary results of single-piece AcrySof have been encouraging. Trivedi and Wilson believe that single-piece AcrySof SA series would be ideal for children. Kugelberg and colleagues also found that SA30AL maintained good centration, produced minimal inflammation and was well tolerated in pediatric eyes. Nihalani BR and Vasavada AR conducted a prospective observational study of 134 eyes of children aged 2–15 years with congenital and developmental cataracts, and found that SA30AL produced satisfactory visual axis clarity, acceptable inflammatory response and maintained good centration. Single piece AcrySof has extremely flexible haptics, combined with excellent memory, which makes the lens easy to implant and not prone to deformation. As the haptics unfold slowly, it is easier to manipulate IOLs in the bag even in the presence of PCCC. One-piece construction is believed to be robust in resisting capsule contracting forces. Also, single-piece AcrySof adapts to the smallest capsular bag without becoming decentered. These unique characteristics have led some surgeons to prefer single-piece over three-piece AcrySof for pediatric cataract surgery. However, long-term clinical experience is necessary to derive firm conclusions regarding the biocompatibility of single-piece AcrySof in pediatric eyes.

Single-piece Acrylic IOLs may not be as effective in preventing epithelial pearls from escaping onto the vitreous face and obscuring the visual axis as are the three-piece Acrylic IOLs because of the wide haptic-optic junctions.

Recently, multifocal IOLs have been suggested for pediatric implants with potential benefits of compensation for presbyopia, functional vision over a broader range of distances, and greater spectacle independence.[114] Some concerns with the placement of multifocal IOLs in children include centration problems, IOL power calculations, the use of silicone IOLs, the amblyogenic effect of multiple overlapping images and decreased contrast, and the tolerability of glare.[115] Caution should be used when considering the insertion of multifocal IOLs in children outside of research protocols at the present time.

Posterior Capsule Capture

Posterior capture of the IOL optic may be carried out after suturing of the incision but before the viscoelastic material is removed. Under and through the viscoelastic, one side and then the other of the IOL optic, 90° form the haptic optic junctions are slipped through the PCCC by means of a spatula or cannula. The haptics remain in the bag (Figure 26-15). Viscoelastic material behind the IOL is left in place, whereas that remaining in the anterior chamber is slowly and carefully removed. Simultaneous irrigation of balanced salt solution (BSS) (preferably with a chamber maintainer) is performed while aspirating the viscoelastic material to maintain a deep chamber and prevent vitreous and the IOL from moving forward. If the PCCC is not 1.5mm smaller than the optic the capture may be lost by the forward movement of the lens as the viscoelastic is removed and before the chamber pressure is restored with BSS. An anterior vitrectomy may be necessary if vitreous herniates at the time of PCCC.

  

 

Figure 26-15  Posterior capsulorrhexis with optic capture.

 

 

Posterior capsulorrhexis with posterior capsular optic capture is a technically challenging procedure. The posterior capsule is thinner than the anterior capsule, adding to the difficulty of achieving a circular opening that is small and concentric to the pupil. In order to have a well-positioned posterior capsulorrhexis captured optic, the PCCC must be reasonably well centered. The lens loops, being in the bag, will exert a strong centering force. The vaulting of the intraocular optic through the PCCC requires cautious manipulation as the posterior capsule is thin. The PCCC seems to have the same stretching capacity as the anterior CCC.[96,][116,][117] The disadvantage of this technique is that it requires skill to avoid peripheral tears in the posterior capsule, which could destroy the integrity of the capsular bag. If the bag integrity is lost before the IOL is placed in the bag a lens may be fixed to the capsule using Rhexis Fixation which is CCC optic capture of a sulcus placed IOL. If, after the IOL is in the bag, the integrity of the posterior is lost for PCCC optic capture and bag fixation is unstable the loops may be left behind the CCC and the optic pulled out through the CCC to capture it and achieve stable capsule fixation. So the PCCC may be done either before the IOL is placed or after the lens is in the bag.

Closure

Most surgeons prefer to suture all the incisions in view of the low scleral rigidity and a child's tendency to rub the eyes (Figure 26-16). Small incisions for foldable IOLs may still require a suture in very young eyes to obtain a watertight closure or to ensure that the wound does not reopen with blinking or eye rubbing. Currently, the most popular suture material for closing corneoscleral incisions in children is 10-0 nylon, 9-0 Vicryl, or 10-0 Vicryl suture.[118] One or more interrupted 10-0 nylon sutures may be required to close the paracentesis site. Peripheral iridectomy is not routinely performed. The chamber is re-deepened after wound closure, and the wound is checked for water tightness. The internal portion of the wound is also checked for gaping or fish mouthing with a sterile Posner gonioscopy mirror (Figure 26-17). Full-thickness corneal sutures of 10-0 nylon are placed as necessary to close the internal wound.

  

 

Figure 26-16  Shoelace suturing techniques.

 

 

  

 

Figure 26-17  Suture technique for repair of fish-mouthing of internal wound.

 

 

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Postoperative treatment

Postoperatively, a child's eye will tend to react with more inflammation than will that of an adult.[6,][51,][119,][120] The inflammatory response can usually be managed well with intensive topical steroid therapy including atropinization.

After cataract surgery in infants, administration of topical steroids and antibiotic drops should be administered using the same routine as in adults. Cycloplegia is gradually tapered off over the ensuing weeks. By 4–6 weeks postoperatively, the child is no longer receiving any eye medication. Suture removal is performed within 2–3 months postoperatively, using general anesthesia if the child is too young to cooperate at the slit lamp, unless absorbable suture has been used. The refractive status can be evaluated at the same time. Amblyopia treatment starts within 1 week postoperatively when the media is clear. Close follow-up by a pediatric ophthalmologist is mandatory until the patient is 10–12 years of age.

Postoperative treatment in children older than 2 years of age should begin immediately at the end of surgery with the instillation of a combination ointment of antibiotic and corticosteroids. Atropine (1%) or homatropine (5%) is also instilled, and the eye is patched until the child fully recovers from the anesthesia. Cycloplegia is continued for up to 1 month after surgery to minimize fibrin deposition.[30] Also, corticosteroid drops are used postoperatively on a tapering schedule for up to 3 months.

In both infants and children, the peak inflammatory reaction does not appear until a day or two after surgery. The surgeon should not be deceived by a very quiet eye the first day after surgery but should remain vigilant in the management of postoperative inflammation in pediatric patients. Because the inflammatory response may be subtle, with few symptoms and only mild ciliary congestion, frequent postoperative visits are recommended.[62] Postoperative synechiae formation is also possible, even though the eye may appear to be quiet. The Nd:YAG laser may be used to break up fibrin strands and to disperse anterior and posterior keratic precipitates on the IOL.

Despite recent advances in pediatric surgical techniques, inadequate preoperative evaluation and postoperative treatment of amblyopia may limit the ultimate visual success in pediatric cases, especially those involving monocular cataract.[120–123] Vigorous occlusion therapy is instituted as early as possible in all cases of unilateral cataract extraction in infancy. Alternate patching may be recommended in patients with bilateral correction.

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Complications of pediatric surgery

Posterior capsule opacification

Posterior capsule opacification is one of the most serious complications because it can lead to irreversible deprivation amblyopia, caused by the insidious formation of retro-pseudophakic membranes. The management and prevention of secondary cataracts, including the proposal of a new technique, are discussed in the section Review of Pediatric Surgical Techniques.

Pharmacological Method to Reduce the Incidence of Secondary Cataract Formation

Tissue plasminogen activator can be used to decrease fibrin following cataract surgery.[124,][125] Experimentally, hirudin has been evaluated for preventing postoperative fibrin formation.[126] Heparin-surface-modified IOLs and even heparin infusion at a concentration of 5IU/mL of infusion of fluid may help prevent secondary membrane.[127,][128] Other experimental methods to reduce secondary membrane formation include antimetabolites, including mitomycin and caffeine acid, phenyl ester, immunotoxins including one in a phase III clinical trial, anti-growth factor agents, agents which inhibit binding of lens epithelial cells to the capsule, and even a gene therapy involving a replication–defective recombinant adenovirus. If toxicity issues can be overcome and these agents can be shown to affect lens epithelial cells (proliferation, migration, adhesion to the capsular bag, and fibrous metaplasia) without collateral damage to ocular tissues, this may represent the future in prevention of secondary membranes. Such agents may in the future be given by single injections, combined with viscoelastic, sustained relapse, or via coating the IOL. The most promising are either gene therapy or specific monoclonal antibodies which selectively target lens epithelial cells.

Sealed-capsule irrigation device has a potential clinical usefulness in reducing visual axis opacification in pediatric eyes. It isolates the interior of the capsular bag from the anterior segment, permitting isolated targeting of lens epithelial cells in vivo using pharmacologic agents while minimizing the risk of damage to other intraocular structures. Early results using demineralized water and Triton X 100 in a histological study in rabbit eyes and some human eyes have been encouraging.[129,][130]

New Techniques to Reduce the Incidence of Secondary Cataract Formation

One of the major concerns in pediatric IOL implantation surgery has been the high incidence of postoperative opacification of the posterior capsule and retro-pseudophakic membrane formation.[37,][63,][131] Residual lens capsule epithelial cells transform to fibroblasts and Elschnig pearls, which proliferate using the posterior capsule, anterior vitreous face, and anterior and posterior surfaces of the IOL as a scaffold.[132,][133] Secondary membranes form, re-occlude the visual axis, and can lead to irreversible deprivation amblyopia. In general, with decreasing age there is an increasing aggressiveness of secondary cataract formation.[134] Different techniques to avoid or reduce postoperative fibrosis or Elschnig pearl formation have been proposed, including primary posterior capsulotomy and anterior vitrectomy, pars plana posterior capsulotomy, and PCCC with posterior optic capture.[32–34,][41,][135–138]

With the development of automated vitrectomy instruments in the 1970s, cutting and aspirating capabilities added a new dimension to the treatment of pediatric cataracts.[60] By performing a posterior capsulotomy and anterior vitrectomy at the time of cataract extraction, a clear optical axis resulted, whereas the need for secondary surgical procedures was minimized. Controversy exists regarding the advisability of performing a primary posterior capsulotomy and anterior vitrectomy versus a posterior capsulotomy at a later date.[43,][117]

The eye in children older than 5 years of age responds to surgery with less inflammation and posterior capsule opacification than does the infant's eye.[49] Also with the development of modern microsurgical techniques and the availability of the Nd:YAG laser, routine primary posterior capsulotomy openings are unnecessary in this population. Leaving the posterior capsule intact for posterior chamber in-the-bag IOL implantation, with the option of Nd:YAG posterior capsulotomy at a later date, may be the best approach in older children and provides the best visual results with the least risk.[62] Secondary Nd:YAG capsulotomy has been demonstrated to be successful in children older than 6 years of age with posterior capsular opacity.[93,][139]

For children younger than 5 or 6 years of age, less cooperative children, and infants, an Nd:YAG laser vertically mounted in the operating room can be used to perform posterior capsulotomies in infants and children either at the time of surgery or weeks to months after the cataract procedure. Laser capsulotomy in the pediatric population, however, requires high energy, and some membranes are too dense to allow penetration of the membrane or a large enough opening. General anesthesia is required, and the recurrence of the membrane is possible because the anterior vitreous face remains as a scaffold for secondary membrane formation.

Studies have demonstrated an inevitable development of secondary cataracts in younger children unless the posterior capsule is opened generously and an anterior vitrectomy is performed at the time of cataract extraction and IOL implantation.[140–142] Many pediatric ophthalmologists currently perform a posterior capsulotomy and a shallow anterior vitrectomy routinely at the time of cataract extraction, prior to insertion of the IOL.[51,][80] Special instruments have been developed to perform a PCCC underneath a posterior chamber IOL.[143]Higher viscous viscoelastics including Healon 5 make this a safer and technically less difficult procedure. One modification involved removing the cataract through a scleral tunnel incision with implantation of a posterior chamber IOL and then, during the same procedure, performing a pars plana posterior capsulotomy and pars plana anterior vitrectomy.[63,][134] It was believed to ensure proper positioning of the IOL prior to performing the capsulotomy, and it was possible to achieve large capsular openings. One disadvantage of primary capsulotomy and anterior vitrectomy is dislocation of the IOLs, which has been demonstrated in 3–20% of cases.[134,][144–146] In addition, there have been reports of cystoid macular edema following pediatric cataract extraction with anterior vitrectomy.[147] Subsequent studies, however, have found the risk of this complication to be quite minimal.[16,][49,][50,][141,][142,][148–151] Anterior vitrectomy may also be associated with vitreous incarceration in the wound and vitreous adhesions that increase the risk of retinal detachment.[56] Finally, even after primary posterior capsulectomy with vitrectomy, many children's visual axes still become re-occluded by secondary membranes,[134,][139,][152] necessitating repeated capsulotomies and sometimes pars plana membranectomy.[49,][71]

Other techniques have been proposed to prevent posterior capsular and vitreous face membrane formation while reducing the risk of dislocation of the IOL. One such technique involves placing the IOL anterior to the entire capsular bag. This creates a tight adhesion between the anterior and posterior capsule and helps prevent lens epithelial cells from migrating, proliferating, and forming Elschnig pearls.[46–49] Another new technique called “bag-in-the-lens” technique described by Marie-José Tassignon and performed in a limited number of cases with excellent results involves a newly designed IOL that fits within an anterior and posterior CCC and sandwiches the capsule leaflets in a peripheral circumferential concavity of the IOL. Successful implantation was achieved in 95% of the cases. At a mean follow-up of 22.7 months, lens epithelial cell proliferation was mild, confined to peripheral capsular bag and bag-in-the-lens optic remained clear.[153]

Posterior Capsulorrhexis with Optic Capture

To further reduce or eliminate opacification of the posterior capsule in pediatric cases while reducing the need for anterior vitrectomy, a technique of posterior capsulorrhexis with optic capture has been shown to be beneficial.[135–138] This technique involves primary posterior continuous curvilinear capsulorrhexis and placement of the optic of the IOL through the posterior capsulorrhexis opening with resultant optic capture while the haptics remain in the bag.[45,][47] This is a technique that has been used in pediatric cases since April 1993 with promising results. The technique for performing posterior capsulorrhexis with optic capture is described later in Current Surgical Techniques.

Primary PCCC with posterior capsule optic capture helps to maintain a clear visual axis, reducing the need for subsequent intervention because of the apposition of anterior and posterior capsule leaflets anterior to the IOL. These capsule leaflets are apposed and anterior to the IOL for 360°, except at the haptic-optic junctions. This causes release of Elschnig pearls to occur anterior to the IOL, where they will be removed by the aqueous (Figure 26-18). Any possible adhesion of protein on the anterior surface of the IOL may be cleared away with the Nd:YAG laser. The benefit of this technique is that it provides excellent IOL fixation and ensures centration of the IOL. The tight barrier which is created prevents vitreous from moving forward. The disadvantages are that the procedure is technically challenging, requires precise and controlled capsulotomies, and makes IOL exchange difficult.[154,][155] Piggyback IOL placement is possible, however. Koch has described that performing this technique in conjunction with anterior vitrectomy is beneficial in preventing posterior capsule opacifications.[154] Primary PCCC with posterior capsule optic capture represents a technique that serves to keep the optical axis clear while maintaining excellent support and centration of the implant.

  

 

Figure 26-18  Posterior capsulorrhexis with optic capture.

 

 

Double Optic Capture with Capsular Fusion

Dr. DeBroff has developed a new technique for infantile cataracts when the surgeon is planning on placing an IOL at the time of surgery. IOL implantation is becoming more accepted for not only unilateral cataracts in infants, but also some cases of bilateral infantile cataracts. This new technique is becoming more frequent with parents who, for financial reasons or because of a lack of dexterity, are unable to maintain contact-lens correction. The high rate of visual axis opacification has been the reason why many surgeons are reluctant to place IOLs in infants. Posterior capsulorrhexis with optic capture has been shown to be an effective technique in children over 2 years of age that effectively creates an apposition of the anterior and posterior capsule leaflets anterior to the IOL, enabling effective sealing of the capsular bag. This technique is very challenging in infants because of the very small size of the eye, the extreme elasticity of the anterior and posterior capsules, and the overall size of the capsular bag.

The technique of double optic capture with capsular fusion involves capturing the optic and, thus, sequestering lens epithelial cells, fixating the IOL optic, preventing IOL movement and decreasing uveal rub. The technique involves performing an anterior CCC, removing the cataract, and performing a primary posterior capsulotomy and anterior vitrectomy using an anterior vitrectomy handpiece. The posterior capsulotomy is enlarged with the vitrectomy handpiece to closely match the size of the anterior capsulorrhexis opening. The ideal size of the capsulotomies would be 1–2mm smaller than the diameter of the IOL optic that is to be implanted. The IOL is placed in the sulcus and the optic is captured through both the anterior capsulorrhexis opening and the posterior capsulotomy opening. In such a manner, double optic capture occurs with the IOL optic posterior to both capsulotomy openings, allowing the capsule leaflets to fuse 360° anterior to the IOL optic. This technique has been utilized for 18 months with no evidence of secondary membranes in 10 eyes and noevidence of increased inflammation, IOL dislocation, or elevated IOP. In addition, the technique of performing the posterior capsulotomy with the vitrector handpiece is technically less difficult than performing a PCCC, but still offers a tear resistant edge in infantile eyes that is amenable to optic capture. Further studies and longer-term follow-up with this technique are planned.

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Glaucoma

Glaucoma is a recognized complication after pediatric cataract surgery. Despite improved surgical techniques, the incidence of glaucoma following successful cataract removal remains high. A significant number of surgeons regard aphakia as a cause of glaucoma. This glaucoma is, however, described as ‘glaucoma in aphakia and pseudophakia’. The most common type of glaucoma to develop following congential cataract surgery is open-angle glaucoma. The risk factors include age at surgery; pre-existing ocular abnormalities; type of cataract; and the effect of lens particles, lens proteins, inflammatory cells and retained lens material. In addition, microcornea, secondary surgery, chronic postoperative inflammation, the type of lensectomy procedure or instrumentation, pupillary block and the duration of postoperative observation have been found to influence the likelihood of glaucoma after pediatric cataract surgery. Certain eye diseases are associated with both cataracts and glaucoma (e.g., Lowe syndrome and congenital rubella). Undergoing lensectomy at a very young age, especially in the first year of life, may be a risk factor for development of glaucoma. It has been suggested that the immaturity of the developing infant's angle leads to increased susceptibility to secondary surgical trauma. Hence some surgeons believe it to be prudent to consider delaying surgery until the infant is 4 weeks old in bilateral cases. Glaucoma can occur at any time after congenital cataract surgery. Therefore, pediatric aphakic and pseudophakic patients should be routinely monitored for glaucoma throughout their lives. The incidence of pediatric pseudophakic glaucoma seems to be less than the incidence in pediatric aphakic glaucoma if the IOL is in the bag or separating the anterior and posterior compartments.

Uveal inflammation

Intense uveal inflammation or severe fibrinoid reaction is a concern, particularly in infants and younger children. The addition of heparin to the irrigating solution has been suggested to reduce postoperative inflammatory reaction and related complications such as synechiae, pupil irregularity and IOL decentration. Atraumatic surgical techniques and in-the-bag fixation are most important contributors which may help to reduce the inflammatory response. Atropine, rather than shorter acting cycloplegics, helps to prevent this fibrinoid reaction that may not be present on the first day or two after surgery, but more typically on the third or fourth day if atropine is not used.

Endophthalmitis

Endophthalmitis is the most serious eye complication after surgery. The incidence has been reported to be 0.07%, which is similar to that reported in the adult population.[156] This complication is the strongest argument against synchronous bilateral surgery in children with bilateral cataracts.[157] Absolute sterility must be maintained and excellent wound closure achieved. Upper-respiratory-tract infection and nasolacrimal duct obstruction should be treated prior to cataract surgery.[157] Careful follow-up of the patient is necessary to observe for any signs of infection, especially in cases of cataracts induced by trauma. Because children and infants are often unable to appreciate or recognize the importance of sudden decreased vision, careful follow-up is essential.

Wound leak

Children often rub their eyes and are often involved in activities of physical contact that can lead to eye trauma. It is important to tightly suture the wound and have the child wear an eye shield until the wound is well healed.

Strabismus

Strabismus is the most common complication following pediatric cataract extraction.[22] The interruption of fusion caused by the lens opacification and possible anisometropia and aniseikonia that follows aphakic correction leads to a 66–86% incidence of strabismus in children who are treated for cataracts.[158,][159] Approximately one-quarter of pediatric patients undergoing cataract surgery may require strabismus surgery.[22]

Amblyopia

Amblyopia is more often associated with monocular than bilateral cataracts. Occlusion therapy, carried out during the postoperative period, is essential.

Nystagmus

The presence of nystagmus indicates poor vision resulting from sensory deprivation[17] and usually will be present if a congenital cataract is not removed by the fourth month of life. If nystagmus is present, the best visual acuity after cataract surgery will usually be less than 20/50.

Retinal detachment

The incidence of retinal detachment after pediatric cataract surgery has been found to be between 1% and 1.5%.[104,][160] With older techniques, such as lens needling, the incidence was as high as 10%.[161] Although the pathogenesis of retinal detachment in pseudophakic patients is not fully understood, secondary changes of the vitreoretinal interface may be important factors.[162,][163] Retinal detachment may occur many years after surgery. The mean age in one series was 31.9 years.[164]

The incidence of retinal detachment after pediatric cataract surgery using PCCC and optic capture, bag-in-lens or Stegmann's optic entrapment (all of these techniques without vitrectomy), has not been studied in large enough series to compare the incidence in cases where primary vitrectomy or later Nd:YAG capsulotomy is used.

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Challenges

Small pupil

Even with mydriatics, the pupils of children especially infants may remain small. This is especially true with cataracts caused by rubella.[101] In addition, use of phenylephrine drops is often contraindicated in infants. Difficulties in performing CCC may be encountered with small pupils. Healon 5 helps to expand a pupil that is not fibrotic. A smooth-edged capsular border can be made larger than the diameter of the small pupil by guiding the tear under the iris while observing the folded edge of the capsular flap. To improve visualization during this procedure, the surgeon may stretch the iris in the quadrant of the advancing tear, using the shaft of the cystotome or a bent needle, or by using a second instrument such as a Y hook or cyclodialysis spatula (Figure 26-19).[165] If emulsification of the cataract is necessary, it should be performed in the central part of the small pupil where visualization is adequate and where the risk of touching the iris or capsule with the tip of the instrument is minimized. Iris trauma should be minimal as the pediatric eyes react in the form of severe postoperative inflammatory response. Iris hooks may be necessary in very small pupil cases.

  

 

Figure 26-19  Improving visualization for continuous curvilinear capsulorrhexis in a small pupil case by stretching the iris with a second instrument.

 

 

Maintaining the intraocular lens centration

A precise CCC that preserves the architecture of the capsular bag is proving to be one of the most important advances in pediatric cataract surgery. The CCC technique increases the probability of safe and secure in-the-bag IOL placement because it maintains the relative integrity of the capsular bag. The visible, flexible rim of a CCC always makes it possible to verify the placement of IOL haptics within the bag and, therefore, guarantees centration (Figure 26-20). Performing CCC in the pediatric population is more challenging than in adults because of the elastic nature of the child's capsule and zonules. Because of the zonular elasticity, centration and size of the CCC may be deceiving. It may be necessary to release the forceps from the anterior capsule as the tear is progressing to allow the lens to assume its natural position. Reinspection is important to ascertain if the tear is progressing in a manner that will create an appropriately sized central capsulorrhexis opening.

  

 

Figure 26-20  Continuous curvilinear capsulorrhexis ensures centration and verification of the intraocular lens haptics in the bag.

 

 

Late decentration of in-the-bag posterior chamber IOL implants is a potential problem with pediatric lens implants. Some contraction of the bag always occurs postoperatively, primarily along the torn edge of the anterior capsule because of fibrous metaplasia of lens epithelial cells and the subsequent contracture of the fibrous membrane attached to the capsule. Anterior capsulectomy techniques, such as the can-opener capsulotomy, the Christmas tree technique, the scissors technique, or any opening that has edge discontinuity, increases the chances of an asymmetrical contracture of the rim. This results in uneven tension on the capsular bag and zonules. Significant decentration is likely to occur if one loop is in the bag and the other is in the sulcus. With CCC, the contracture is symmetrical if the capsular opening is circular, central, and smaller than the optic of the IOL. If the CCC is outside the edge of the optic on one side of the optic the adhesion of the CCC edge there to the posterior capsule may progressively nudge the IOL to the other side and result in eccentricity of the IOL, even though it was once centered and it is still in the bag.

If a short anterior capsule tear occurs in the pediatric anterior capsule CCC border without extension to the equator, it can be blunted or turned back toward the CCC by using forceps (Figure 26-21). The opening will be eccentric, but the smooth continuous rim prevents radial extensions of tears in elastic pediatric capsules. If a longer anterior capsule tear occurs, care must be taken during cataract removal to prevent excessive pressure that could extend the tear past the equator and into the posterior capsule (Figure 26-22). In such cases, the irrigation–aspiration or ultrasound should be carried out with the handpiece kept centrally over the capsulotomy, avoiding stress to the anterior capsule rim. The irrigation–aspiration should be slow with fewer movements for vacuuming of cortical material.

  

 

Figure 26-21  Turning back a radial extension of the continuous curvilinear capsulorrhexis tear.

 

 

  

 

Figure 26-22  Pressure during phacoemulsification in the presence of an anterior capsular radial tear causing extension of the tear.

 

 

When an anterior capsule tear occurs, cohesive viscoelastic agents may be useful to help avoid an extension around to the posterior capsule during IOL insertion. However, the viscoelastic agent should be injected carefully, adding a little above and then below the torn edge to sandwich it within the viscoelastic material. If the capsular bag is filled without significant viscoelastic material above the capsule, the pressure within the bag can extend the tear. The IOL haptics should be oriented perpendicular to the tear. In addition, the anterior capsule tear can be matched by creating a second anterior capsule tear 180° away from the first. This precaution ensures symmetrical tension on the anterior capsule rim as the capsule contracts postoperatively (Figure 26-23). Consistent in-the-bag IOL centration can be achieved by analyzing the configuration and locating the anterior capsule defects.

  

 

Figure 26-23  Anterior capsular tear matched with second anterior capsular tear 180° away to ensure symmetric tension on the anterior capsular rim.

 

 

Anterior capsule ring contracture

Although there are multiple advantages of CCC, there is one potential complication peculiar to the technique. In adults with weakened zonules or after trauma in any age group, significant contraction of the capsule may occur along the edge of the tear a few months postoperatively. Unlike the situation after irregularly torn capsulotomies, this contracture rarely leads to any significant degree of IOL decentration, as there is usually a symmetrical contracture of the CCC. Anterior capsule ring contracture can be released using the Nd:YAG laser. Radial peripheral placement of Nd:YAG pulses in the contracted anterior capsule releases the contracture of the capsule and prevents early or late decentration of the IOL. The Nd:YAG successfully releases this anterior capsule purse-string effect.[49]

Posterior capsular tears

PCCC may be employed in the making of a primary posterior capsulectomy, as previously described. It may also be used when a small linear or triangular tear inadvertently occurs in the posterior capsule; even though the posterior capsule is resistant to radial tears and, thus, maintains capsular bag integrity (Figure 26-24).[166] Tears of the posterior capsule that have not extended as far as the capsular equator are candidates for PCCC. The rounding off of a posterior capsule tear or completing it full circle usually prevents extension of the tear, which can frequently occur during anterior vitrectomy or lens placement. Thus, PCCC should be performed prior to anterior vitrectomy or lens insertion when a small posterior capsule tear has occurred. Also, if a stalk of a persistent hyaloid membrane is present, Vannas scissors can be used to sever it after completing PCCC.

  

 

Figure 26-24  Appearance of a small tear in the posterior capsule.

 

 

The goal is to direct the advancing tear into a circle that encompasses the entire extent of the tear. Alternatively, one or both ends of a linear tear may be rounded and blunted by means of PCCC techniques. For maximal control when redirecting a tear of the posterior capsule, capsulorrhexis forceps are used to grasp the capsule flap near one point of the tear and to turn the tear in the desired direction (Figures 26-25,26-26). The PCCC is kept as small as possible to preserve maximal integrity of the posterior capsule.

  

 

Figure 26-25  Posterior continuous curvilinear capsulorrhexis (CCC) technique for blunting small tears in the posterior capsule is identical to anterior CCC.

 

 

  

 

Figure 26-26  Posterior tear cannot enlarge after completion of posterior continuous curvilinear capsulorrhexis.

 

 

Pre-existing posterior capsule defects and posterior lentiglobus

Posterior lentiglobus tends to distort the preoperative retinoscopy reflex – a condition that makes optical correction of refractive errors difficult.[10,][167–169] Early detection of this condition and other conditions that produce higher-order optical aberrations will be facilitated by the more general availability of wavefront sensing instruments. Cataract extraction should be performed as soon as any decrease in visual acuity occurs that is unamenable to optical correction and amblyopia therapy.[150] Because the posterior capsule in these patients is thinned and weakened centrally, hydrodissection should never be performed, as this can create a posterior capsule rupture. “Hydro-free” fluidless dissection can be used to aid in dissection of the cortex from the anterior capsule prior to aspiration or phacoemulsification of the lens (Figures 26-27,26-28).[170,][171]

  

 

Figure 26-27  Hydro-free dissection: achieving dissection of the cortex from the capsule without injecting fluid inferiorly.

 

 

  

 

Figure 26-28  Hydro-free dissection superiorly through the paracentesis wound.

 

 

Pre-existent defects or splits in the posterior capsule (as in posterior lentiglobus or perforating trauma) may also be managed by PCCC. Complete PCCC may not be possible, depending on the configuration and extent of the split of the lentiglobus. However, the technique may still possibly be used to round off the points of the leading tears. Pre-existing defects may be associated with degenerated vitreous which needs to be removed with vitrectomy. The capsule is weak in most of these cases, in which case the IOL should be placed in the sulcus. Sometimes an IOL may be placed in the bag with its loops perpendicular to the tear. If the IOL is not stable and secure in the capsular bag with this method, the optic should be pulled out through the CCC for optic capture (reverse rhexis fixation) or it should be removed from the bag and placed in the sulcus. To assure centration following this maneuver and to avoid late complications such as transillumination defects, glaucoma and hyphema, especially when Soemmering's rings develop, the optic should then be pushed through the anterior CCC into the bag.[172]

Posterior capsule plaques

PCCC can also be employed for the removal of thickened fibrotic posterior capsule plaques. In these cases, the PCCC is made as a controlled circle that encompasses the central opacity and results in a posterior capsule opening that resists extension to the equator. This capsular opening can be made before or after the IOL is implanted in the capsular bag. By nudging the IOL eccentrically and slipping a barbed needle on a syringe of viscoelastic material under the lens, PCCC is achieved. This technique was successfully used in 1987 for the removal of dense plaque from the posterior capsule of a 7-year-old boy who had acquired a cataract secondary to irradiation for rhabdomyosarcoma.[112] If the posterior capsule plaque is too large involving the entire posterior capsule, a central nick should be placed in the central posterior capsule with a slit knife and the plaque can be cut with scissors and/or a vitrectome with the port facing superiorly. The Fugo blade is another option.

Eye growth and changing refraction

Predicting axial growth, and the refractive changes that accompany it, are major challenges for the long-term care following pediatric cataract surgery. This is especially true with the wide-spread acceptance of fixed-power IOL implantation. Unless the growth of the eye can be accurately predicted, selection of IOL power is a difficult task.

Axial growth after cataract surgery can be attributed to normal eye growth and other factors, including age at surgery, visual input, the presence or absence of IOL, laterality and genetic factors. The interocular axial length difference was found to be another important variable influencing axial growth. Understanding pediatric eye growth will help in IOL power calculation and the prediction of refractive changes after IOL implantation.

Secondary intraocular lenses in children

The need for secondary IOLs in children occurs frequently because many infants are left aphakic following cataract surgery due to their small size and young age, and because of the difficulty of using aphakic contact lenses in children (Table 26-1). In addition, secondary IOLs may be needed in children left aphakic after traumatic cataracts. Some pediatric IOLs may require removal and replacement with a secondary IOL because of Nd:YAG pitting or subluxation. Older children and young adults may find the optical aberrations of aphakic spectacles disabling. Children with nystagmus may not tolerate aphakic spectacles or contact lenses. The effective use of secondary IOLs in children has been described.[173–179]


Table 26-1   -- Secondary intraocular lenses in children

  

I.   

Indications

  

a.   

Failure of contact lens

  

b.   

Nystagmus

  

II. 

Preoperative considerations

  

a.   

IOL calculation and measurements

  

i.    

Patient cooperation

  

ii. 

A scan

  

iii. 

Keratometry

  

iv. 

Cycloplegic refraction

  

v.   

Refraction goal

  

b.   

Capsular support

  

III. 

Technique

  

a.   

In the bag

  

i.    

Technique – Wilson et al

  

b.   

Sulcus fixated lens

  

i.    

Simple

  

ii. 

Optic capture

  

iii. 

Capsular membrane sutured lens

  

c.   

Iris fixated lens

  

d.   

Scleral sutured lens

  

IV. 

Complications

  

a.   

Vision decrease (5.8%)

  

b.   

IOL decentration (Crnic 5%) (Trivedi & Wilson 5%)

  

c.   

Wound leak (5%)

  

d.   

Secondary membrane (Crnic 9%) visual axis opacification (5.2% Wilson)

  

e.   

Pupillary block glaucoma (2%)

  

f.    

Ptosis (2%)

  

g.   

Glaucoma

  

h.   

Dislocation of IOL (2.6% Wilson)

  

i.    

Pupillary capture (1.3% Wilson)

  

j.    

Decentration with simple sulcus-fixated foldable IOL – inferior in males? not seen in PMMA, worse if axial length >23mm (28.6% Wilson)

 

Careful preoperative planning optimizes results. Preoperative considerations include the ability of the child to cooperate with sitting for axial length and keratometry measurements. If a child cannot cooperate in the clinic setting, then these must be planned under a separate sedation or under general anesthesia at the time of the procedure. Cycloplegic refraction and the goal refraction for the operated eye are considered. Refraction in the sound eye should also be performed to help avoid anisometropia, which may be amblyogenic. The surgeon should also evaluate the patient for the presence of adequate capsular support and the presence of synechiae, which may make positioning of a lens difficult.

Finally, the type of procedure and the lens appropriate for the procedure are chosen. Patients with adequate capsular support may be well-served by a variety of procedures. In-the-bag placement, membrane optic capture, or IOL membrane suture fixation is always desirable for improved centration, sequestration of the lens from uveal elements, and the long-term stability needed for the decades to come in these young children. When possible, the authors employ a technique independently described by Wilson et al. for in-the-bag secondary IOL placement for patients with a Soemmering's ring. The anterior capsule near the apposed edge of the capsular leaflets is opened, followed by aspiration of the epithelial elements between the leaflets. The IOL is then placed in the bag, between the opened leaflets of the Soemmering's ring.[176]

Optic capture is another method affording excellent centration and long-term stability for secondary IOL placement.

In patients with membrane support, but not an appropriate opening for membrane optic capture the authors consider suturing the IOL to the capsular membrane for stable fixation and to avoid iris contact.

In patients without adequate capsular support, a scleral or iris-sutured secondary IOL may be considered. Iris-fixated lenses are demonstrating their effectiveness and a reduction in the risk of endophthalmitis that may occur with scleral-sutured posterior chamber IOL.

Because support for the IOL is more difficult to achieve, one of the most significant complications of secondary simple sulcus IOL placement is IOL decentration, which occurs in about 5% of cases.[178,][179] In none of these reported cases was optic capture, membrane suturing, or Soemmering's ring bag placement used. In a series by Trivedi and Wilson, all decentrations occurred in sulcus-fixated foldable IOLs and none occurred in sulcus-fixated PMMA lenses. Males with axial length of >23mm were especially susceptible in this series.

Other reported complications include vision decrease (5.8%), wound leak (5%), secondary membrane (9%: Crnic), visual axis opacification (5.2%: Wilson), pupillary block glaucoma (2%), ptosis (2%), dislocation of IOL (2.6%: Wilson), and pupillary capture (1.3%: Wilson).

Functional outcome

Congenital cataracts cause visual deprivation that results in severe amblyopia. Changing refraction with amblyopia poses a grave challenge to visual rehabilitation. Strabismus is another factor influencing visual rehabilitation following pediatric cataract surgery. Despite a satisfactory technical outcome, functional outcome remains unpredictable.

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Conclusions

Given the characteristics of children's eyes, pediatric cataract surgery is technically challenging. Tissue elasticity, a propensity for postoperative inflammation, and a high rate of secondary cataract formation are matters of concern. The surgical techniques are more demanding and there is less room for error. Also, diligent preoperative and postoperative management is essential for satisfactory visual results. The timing of surgery is often crucial to prevent deprivational amblyopia and to attempt the preservation or restoration of binocular vision. The surgeon must be cognizant of the many complications that may occur in pediatric cataract surgery and must be prepared to manage any that do arise.

Longer-term follow-up of larger IOL series should continue to support the safety and efficacy of posterior chamber IOL implantation after cataract extraction in infants and children. With continued improvements in surgical and laser techniques, IOL designs, anti-inflammatory agents, and amblyopia therapy, the refractive and visual outcomes in pediatric cataract surgery should continue to improve, whereas the need for secondary procedures should diminish.

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Further Reading

Asrani S., Friedman S., Hasselblad V., et al: Does primary intraocular lens implantation prevent “aphakic” glaucoma in children?.  J Pediatr Ophthalmol Strabismus  2000; 4:33-39.

Mackool R., Chhatiawala H.: Pediatric cataract surgery and intraocular lens implantation: a new technique for preventing or excising postoperative secondary membranes.  J Cataract Refract Surg  1991; 17:62-66.