Hospital for Sick Children's, The: Atlas of Pediatric Ophthalmology & Strabismus, 1st Edition

10

Glaucoma

Alex V. Levin

  1. Raymond Buncic

Elise Héon

Glaucoma may manifest at any time during childhood. Congenital and infantile glaucoma usually involves a primary dysgenesis of the trabecular meshwork system, whereas later onset often implies a secondary malfunction of aqueous outflow. The primary childhood glaucomas, congenital/infantile and juvenile, have a genetic basis, which is currently being elucidated. Other forms of glaucoma associated with congenital malformation of the anterior segment such as the Axenfeld-Rieger spectrum and aniridia, also have a genetic basis. Virtually every anterior segment dysgenesis leaves the patient with a lifelong risk of developing glaucoma.

Some children acquire glaucoma as a result of other events. Aphakic glaucoma is one of the most common causes of pediatric glaucoma. Any child who has cataract surgery is at lifelong risk and must be screened for glaucoma periodically. Some aphakic children may also have a goniodysgenesis, perhaps indicating that there is more to the malformation complex than just the cataract. Other theories for the development of aphakic glaucoma include barotrauma at the time of surgery, communication of the anterior chamber with the vitreous, and genetic predisposition. The average onset time for developing glaucoma is approximately 8 years after cataract surgery. The effect of intraocular lens implantation is not yet clear, but early indicators suggest that this procedure will not reduce the incidence of glaucoma significantly, particularly in the first 2 years of life.

Trauma can also result in glaucoma through direct damage to the aqueous outflow system, inflammation, hyphema, or secondary ghost cell glaucoma. Other causes of secondary glaucoma include infection such as congenital rubella syndrome, uveitis, and the use of steroids. Glaucoma may be an isolated ocular disorder or associated with a wide variety of systemic diseases and syndromes. This chapter focuses on isolated glaucoma. The reader is referred elsewhere in this atlas for discussion of those ocular and systemic disorders that are associated with glaucoma, such as Sturge-Weber syndrome and neurofibromatosis type 1 (Chapter 23: Phakomatoses) and aniridia and Axenfeld-Rieger syndrome (Chapter 6: Iris and Pupils).

The most common cause of visual loss in patients with glaucoma is amblyopia. However, left untreated, the glaucoma itself will result in optic neuropathy with visual field and acuity loss. Early identification, aggressive treatment, and careful periodic follow-up are the cornerstones of a successful outcome.

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Figure 10.1 Primary Congenital Glaucoma—Buphthalmos

Elevated intraocular pressure in the eye of a child less than 2 to 3 years old results in stretching of the pliant sclera and cornea such that the corneal size and axial length increase. Rarely, this can also occur later, in the first 5 to 7 years of life. Buphthalmos will also be reflected in an increasingly myopic refraction. In microphthalmic eyes, the corneal diameter and axial length may be increasing pathologically, even though the absolute values are below the age-matched normative data. Likewise, excessive loss of hyperopia (e.g., in an aphakic eye) can also be a sign of excessive ocular growth due to glaucoma. In the left image, the child's left eye was enucleated (photograph provided by John Ainsworth, Hospital for Sick Children fellow, 1994). In the right image, the child has left microphthalmia with a buphthalmic right eye that was also previously microphthalmic.

 

Figure 10.2 Primary Congenital Glaucoma—Corneal Edema

Corneal edema can occur in both primary and secondary forms of early childhood glaucoma. Epithelial edema is usually reversible with prompt control of the glaucoma. As shown here (left imageleft eye), the edema results in a mild haze that obscures the view of the anterior segment. Subtle epithelial edema can be revealed by touching a blunt instrument to the cornea and observing a bluish “pitting” response. Stromal edema (right image) reflects a more chronic edema and is usually more opaque. Corneal transplant may be necessary but over time, the cornea may clear without intervention other than glaucoma control. Unfortunately, the clearance is almost always from peripheral to central, thus leaving the visual axis impaired and the child at risk for irreversible amblyopia if the transplant is deferred too long.

 

Figure 10.3 Haab Stria

Haab stria is one of the cardinal manifestations of early pediatric glaucoma. It represents a break in the Descemet membrane due to stretching secondary to elevated intraocular pressure. The visible lines represent the scrolled back edges from the break. There may or may not be overlying corneal changes: Three variations can be seen. Shown here are Haab stria with no stromal scarring at edges (left image) and with white stromal scarring at edges (right image). In Figure 10.2, right image, the stromal scarring is occurring throughout the width of a Haab stria, the edges of which can be seen at the upper and lower border of the scar. Note the usual scalloped edges and multidirectional patterns, much unlike the straight-edged vertically oblique breaks due to forceps injury (Chapter 5: Cornea, Fig. 5.21). The cornea of early primary pediatric glaucoma may have reduced pachymetry or, in the presence of edema or glaucoma associated with aphakia, aniridia, or other anterior segment dysgeneses, elevated pachymetry. The intraocular pressure reading must be interpreted accordingly.

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Figure 10.4 Primary Congenital Glaucoma—Iris Changes

These two images demonstrate some nonsyndromic unusual anterior segment dysgenesis patterns, that may be associated with primary congenital/infantile glaucoma. The current genetic nomenclature for glaucoma refers to the congenital primary glaucomas as GLC3 with a letter added thereafter referring to the gene identified in chronological order. GLC3A refers to congenital/infantile glaucoma due to mutations in the CYP1B1 gene at 2p21. Any genetic form of congenital glaucoma may still present with variations in anterior segment morphology. An abnormal iris should serve as a marker for possible glaucoma risk, particularly when the pattern differs from other family members and there is a concern that the child may be affected.

 

Figure 10.5 Primary Congenital Glaucoma—Gonioscopy

Historically, primary congenital glaucoma was included in the “anterior segment cleavage disorders,” recognizing that its pathophysiology in part lies in the failure of proper angle differentiation. Clinically, histologically, and particularly during goniotomy surgery, one can often see a gray-white membrane covering the iris insertion and trabecular meshwork, which has been referred to as the Barkan membrane, although there has been some controversy over the nature of this structure. As shown here in these gonioscopy photos, the iris insertion is abnormally high either uniformly (left image) or in patches (right image). There may be increased vascularity or peripheral iris atrophy (Fig. 10.4). Other forms of goniodysgenesis include iridogoniodysgenesis (6p25 and 4q25) and iridogoniodysplasia (6p25) syndromes.

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Figure 10.6 Early Childhood Glaucoma—Optic Neuropathy

Unlike adults, optic nerve cupping in young children is initially a reflection of bowing backward of the lamina cribrosa rather than nerve fiber loss. As a result, control of intraocular pressure may be associated with dramatic reversal of cupping. When nerve fiber layer loss does occur, there is still more concentric enlargement of the cup rather than the temporal sloping of adult glaucoma, although temporal pallor may occur. Visual field loss in children is harder to assess, but when possible, it usually reflects the pattern of optic nerve change with fairly symmetrical constriction early in the disease. The role of optical coherence tomography (OCT) and Heidelberg retinal tomography (HRT) in following children with glaucoma is currently being explored, and normal age-related values for nerve fiber thickness, much thicker in children, are being developed. Optic nerve notching and hemorrhage are very rare in children.

 

Figure 10.7 Early Aphakic Glaucoma—Anterior Segment Changes

Less commonly, glaucoma can develop in the early postoperative period following cataract surgery. This may be due to an abnormal anterior rotation of the iris–ciliary body complex or may simply be an unusual manifestation of uncomplicated aphakic glaucoma; however, more often it is the result of the aggressive inflammation that characterizes the response of the pediatric eye to surgery. The angle may be closed by peripheral anterior synechia or there may be midperipheral iridocorneal adhesions. Medical treatment rarely succeeds and surgical reduction of intraocular pressure (IOP) becomes necessary. However, if iritis is controlled and IOP lowered surgically, the prognosis can be quite favorable and long-term treatment may not be needed.