Albert & Jakobiec's Principles & Practice of Ophthalmology, 3rd Edition

CHAPTER 180 - Lattice Degeneration, Cystic Retinal Tufts, Asymptomatic Retinal Breaks, and Additional Selected Peripheral Retinal Findings

Charles P. Wilkinson

INTRODUCTION

A thorough examination of the peripheral retina frequently reveals entities that are of varied importance as factors associated with rhegmatogenous retinal detachment (RRD). The most significant of these is a retinal horseshoe tear occurring in association with symptoms of a posterior vitreous detachment (PVD), because this type of symptomatic tear usually will lead to clinical RRD. At the other end of the spectrum is a group of incidental congenital or acquired entities that are of little importance other than their potential for being misdiagnosed as important.

This chapter includes descriptions of a variety of focal changes in the periphery of the retina. Other than the type of retinal tear mentioned above, the most important of these is lattice degeneration. Cystic retinal tufts are also visible sites of vitreoretinal adhesion and have some potential to be sites of later retinal tears. Retinal breaks are responsible for RRD, but most literal breaks are not dangerous. Similarly, most of the additional peripheral retinal abnormalities described in this chapter have little potential to cause RRD. The author is indebted to the authors of chapters that appeared in previous editions of this publication and described similar fidings.[1-3]

 

 

LATTICE DEGENERATION OF THE RETINA

Synonyms

  

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Snail track degeneration

  

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Pigmentary degeneration

  

.   

Retinal erosion

  

.   

Equatorial degeneration

Lattice degeneration, a vitreoretinal disorder with distinctive features, is the most important visible fundus lesion predisposing to retinal tears and detachment. Lattice degeneration is typically characterized by sharply demarcated oval or round areas that are oriented circumferentially and are associated with liquefaction of the overlying vitreous gel and firm vitreoretinal adhesions along the edges of the lesions. Vitreous traction on these areas after PVD is often responsible for retinal tears. Lesions clinically and histopathologically indistinguishable from isolated lattice degeneration have been observed in various hereditary disorders associated with retinal detachment.[4]

 

 

EPIDEMIOLOGY

The prevalence of lattice degeneration ranges from 6% to 10% in nonselected patients and reaches a maximum prevalence during the second decade of life.[5] There is no statistically significant difference between males and females, and left and right eyes are involved with equal frequency. The prevalence of lattice degeneration is not related to race. Bilateral involvement is observed in 34-42% of patients in clinical studies[5] and in 48% of cases in an autopsy series.[6] The location and appearance of the lattice lesions tend to be symmetric when both eyes are involved.

Key Features

  

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Sharply demarcated ovoid lesions

  

.   

Variable pigmentation

  

.   

White lines crossing lesion

  

.   

Retinal thinning

  

.   

Overlying vitreous liquifaction

  

.   

Firm vitreoretinal adhesions at margins

Most reports have described a positive correlation between the incidence of lattice degeneration and myopia. Karlin and Curtin[7] correlated axial length measurements with the incidence of lattice degeneration in over 1400 myopic eyes. Lattice degeneration was observed in ?15% of eyes with axial lengths of 30 mm or more, whereas it was present in less than 7% of eyes with axial lengths of 27 mm or less. However, Yura[8] did not discover such a linear relationship in myopic cases, and he observed differences among eyes with additional myopic pathology. Of eyes with axial length 26-31 mm, the greatest incidence of lattice degeneration was in the first group. Regardless of axial length, the incidence of lattice degeneration was significantly higher if the eye did not exhibit a posterior staphyloma. Lattice degeneration is not restricted to eyes with myopia. Clinical studies found that ?25% of eyes with lattice degeneration are emmetropic or hyperopic.[4, 5]

 

 

PATHOGENESIS

Theories regarding the pathogenesis of lattice degeneration include: (1) primary choroidal changes, (2) embryologic vascular anastomoses, (3) vitreous traction due to a primary disorder of the vitreous, (4) retinal ischemia, and (5) a primary defect in the internal limiting lamina of the retina.[4] The earliest and most severe changes occur in the inner retinal layers, and the choroid is usually not involved.[6]Therefore, it is unlikely that lattice degeneration is due to a primary choroidal disorder. Similarly, lack of evidence makes it unlikely that embryologic vascular anastomoses between vitreous and retinal vessels are the cause. A primary vitreopathy or vascular theory also does not adequately explain many features of lattice degeneration. Although both electron microscopy and trypsin digestion techniques have shown that the inner limiting lamina is absent over many lattice lesions, primary defects in the internal limiting lamina would be expected to be caused by anomalies in the adjacent Müller's cells, and this has not been demonstrated.[4] Thus, the pathogenesis of lattice degeneration remains unknown.

 

 

CLINICAL FEATURES

Several features of lattice degeneration may be observed individually or in various combinations.[4, 5] Lattice lesions have abrupt borders and are usually ovoid, although some are round. They are usually circumferentially oriented and may occur in multiple rows (Fig. 180.1). Liquefaction of the overlying vitreous gel can be observed by indirect ophthalmoscopy and scleral depression or by slit-lamp examination with a contact lens. The most conspicuous feature(s) of the lesions may be one or a combination of the following: (1) lattice-like white line changes in the crossing retinal vessels, (2) snail track variations, (3) alterations in pigmentation, and (4) ovoid or linear reddish craters.[4, 5] Round atrophic holes within lattice lesions, and/or retinal tears due to traction at the ends or the posterior border of the lesions, may occur as secondary changes. Case-to-case variations in these features probably account for the variety of terms used to describe lattice degeneration.

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FIGURE 180.1  Clinical appearance of lattice degeneration. Two parallel rows, the upper (arrow) paravascular in orientation without pigmentation, shows surface white dots and vascular sheathing. The lower pigmented patch of lattice shows a prominent interlacing pattern of white lines, representing hyalinized blood vessels.

 

 

White lines often associated with lattice degeneration are a striking clinical feature in some cases and are responsible for the term used to describe this condition (Fig. 180.1). These segments are retinal blood vessels crossing the lesion, and a blood column is usually visible at each end. 'Pseudo white lines' can also be seen within lattice lesions because of linear distributions of yellowish flecks.[5]Histopathologically, the white line appearance is due to stromal fibrosis and a cellular thickening of the vessel wall (Fig. 180.2).[6] The lumen of the vessel is narrow, and fluorescein angiography demonstrates delayed filling of these segments in over 50% of cases. White line changes have been reported in 17-30% of patients with lattice degeneration, and they are present in ?12% of isolated lattice lesions.[4, 5]White line changes are less common inyounger patients. Byer[5] discovered them in 3% of patients with lattice degeneration during the second decade of life, and the prevalence increased to 43% in patients over age 50.

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FIGURE 180.2  Histopathologic appearance of lattice degeneration. Cross-sectional view with anterior border to the left. Separation of the sensory retina from the pigment epithelium is a fixation artifact. V indicates condensed sheets of vitreous collagen firmly adherent to anterior and posterior borders. The asterisk represents an overlying pool of liquefied vitreous. The arrow shows a thick-walled, hyalinized blood vessel.

 

 

The snail track variation describes lattice lesions with a shiny, wet appearance, which is due to multiple tiny, yellowish-white flecks that appear to lie on the inner surface of the retina (Fig. 180.3). These flecks have been observed in up to 80% of lattice lesions, although the extent varies considerably.[5] The cause of these flecks is unknown, but they are probably atrophic or degenerative.

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FIGURE 180.3  Snail track degeneration. Generally acknowledged to be a form of lattice degeneration, this lesion has a frosted appearance of yellowish-white flecks and lacks the characteristic crisscrossing white lines.

 

 

Prominent pigmentary changes associated with lattice degeneration are so common that this entity was previously called 'pigmentary degeneration'. Pigmentary changes have been reported in 82-92% of lesions. The pigmentary changes are nonspecific and are due to retinal pigment epithelial hypertrophy, hyperplasia, and migration into the overlying sensory retina. Four variations in the pigmentary alterations have been described: (1) diffuse hyperpigmentation with scattered clumps or granules throughout the lattice lesion; (2) pigmentary deposits along the retinal blood vessels passing through the lesion; (3) round areas of gray, altered pigmentation associated with tiny focal retinal detachments due to round atrophic retinal holes within the lattice lesion; and (4) narrow demarcation lines around focal detachments associated with small atrophic breaks (Fig. 180.4).[4] Discrete areas of depigmentation also occur within some lattice lesions. The pigmentary changes seem to be secondary to changes in the overlying sensory retina. Alterations in the pigment epithelium may be helpful intraoperatively in localizing the spot on the sclera corresponding to a retinal break when the retina is highly elevated.

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FIGURE 180.4  Simultaneous formation of a horseshoe tear and an operculated tear (eye bank eye). The more posterior operculated tear was produced by stronger vitreoretinal traction than was on the flap of the horseshoe tear.

 

 

RETINAL HOLES

Round atrophic retinal holes within areas of lattice degeneration are typically small, measuring less than 0.3 mm (Fig. 180.5). Most round holes are solitary, although multiple holes may be present within a lattice lesion. In clinical studies, round holes have been reported in ?17% of lattice lesions and 35% of eyes with lattice lesions.[4] Atrophic holes within lattice lesions aremore than twice as common in the inferior quadrants as in the superior quadrants, and they occur more frequently in older patients. The clinical importance of atrophic holes is that they occasionally cause or contribute to retinal detachment, and this occurs most frequently in myopic eyes of relatively young patients with lattice degeneration. This topic is discussed in more detail in a later section.

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FIGURE 180.5  Retinal holes. Round atrophic retinal holes may be found in lattice degeneration or without another apparent pathologic condition. They are not caused by vitreous traction.

 

 

 

 

RETINAL TEARS

Flap ('horseshoe') retinal tears along the lateral and/or posterior edges of lattice degeneration lesions are almost invariably associated with PVD (Figs 180.6 and 180.7). The incidence of tears along the edge of lattice lesions is low, but such breaks are important in the development of retinal detachment, and this topic is discussed in more detail in a later section.

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FIGURE 180.6  Pathogenesis of traction tears in lattice degeneration. (a) Vitreous condensations adhere firmly to the borders of a superior circumferential patch of lattice degeneration. (b) Posterior vitreous separation. The force of gravity increases traction transmitted along sheets of vitreous condensation. (c) A traction tear begins as the retina rips along the line of vitreoretinal adhesion. The tear will assume the typical horseshoe configuration as the anterior vector of traction force increases after the posterior rip, creating radial extensions toward the ora serrata at each end of the patch of lattice degeneration.

 

 

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FIGURE 180.7  Large traction tear in lattice degeneration. Bullous detachment is to the right of the tear (posterior), and lattice degeneration is elevated in the flap to the left (anterior).

 

 

 

 

RETINAL DETACHMENT

The risk of retinal detachment due to lattice degeneration is relatively small. The incidence of lattice degeneration in the general population is 6-10%, whereas that of retinal detachment is ?0.01% per year.[9, 10] Further, 68-80% of retinal detachments are not associated with lattice degeneration.[11] Still, eyes with lattice degeneration are more likely to develop retinal detachment. The risk of developing a retinal detachment in patients with lattice degeneration has been calculated to be 0.3-0.5%.[10, 12] Byer[13] followed 423 eyes with lattice degeneration for 1-25 (average 10.8) years and observed clinical retinal detachments in three (0.7%).

In patients with retinal detachment in one eye, the chance of retinal detachment occurring later in the fellow eye is at least 10%. Estimates of the prevalence of lattice degeneration in the fellow eye of patients with retinal detachments range from 9% to 35%.[4] Although fellow eyes with lattice degeneration are predisposed to develop retinal tears and detachment, retinal breaks often do not occur at the sites of these visible vitreoretinal adhesions.[14]

 

 

PATHOLOGY

Gross and microscopic pathologic features include: (1) retinal thinning with loss of retinal neurons; (2) liquefaction of the adjacent vitreous, absence of vitreoretinal attachments, and also absence of the internal limiting membrane over the lesions; (3) thickening and hyalinization of retinal blood vessels; and (4) vitreous condensations with firm vitreoretinal attachments at the margins of the lesions (Fig. 180.2).[6] Varying degrees of pigmentary alteration also occur in over 90% of lesions. As noted above, round atrophic retinal holes are frequently present. Retinal tears along the lateral or posterior edges of the lesions are present, but they are uncommon, particularly in the absence of a PVD. With the exception of prominent vitreoretinal attachments at the margins, all other histopathologic fidings are more pronounced near the center of the lesion. In advanced cases, glial proliferation may extend from the retina into the vitreous cavity along the condensed interface between the liquid and vitreous gel compartments (Fig. 180.2).

 

 

DIFFERENTIAL DIAGNOSIS

The clinical appearance of lattice lesions is usually apparent to experienced observers who employ indirect ophthalmoscopy and scleral depression. However, a variety of focal abnormalities are frequently misinterpreted as lattice lesions by relatively inexperienced individuals. These entities include in particular focal chorioretinal scars and paving stone ('cobblestone') degeneration, and the latter disorder is discussed later. With experience, the distinction between lattice degeneration and mimicking lesions becomes relatively easy.

 

 

TREATMENT

Lattice degeneration is present in ?30% of retinal detachments, and ?94% of these detachments occur in primary (nonfellow) eyes.[14] Because lattice lesions are common in the population, they have commonly been considered as candidates for prophylactic therapy.

PRIMARY (NONFELLOW) EYES

Byer's natural history study of 276 patients and 423 involved eyes, followed an average of almost 11 years, indicated that lattice lesions in phakic nonfellow eyes were not particularly dangerous.[13] At the end of the follow-up period, atrophic retinal holes were present in 150 (35%) eyes. Subclinical retinal detachments, defied as subretinal fluid extending more than one disk area from the break but not posterior to the equator, were observed in 10 of the eyes with holes. In six of these eyes the subclinical detachment developed during the observation period, whereas four eyes exhibited the changes at the initial exam. Only one subclinical detachment was considered in need of treatment after a small asymptomatic posterior extension of subretinal fluid.

Four asymptomatic tractional retinal tears were observed in three of these 423 eyes at the initial examination, and symptomatic tractional tears without clinical detachment developed in five additional eyes during follow-up.[13] Three of five symptomatic and all asymptomatic breaks occurred adjacent to lattice lesions. All symptomatic breaks were successfully treated; no asymptomatic tractional tears were treated, and none changed over follow-up periods of 7, 10, and 15 years. Clinical retinal detachments developed in three of the 423 eyes.[13] Two were due to round retinal holes in lattice lesions of patients in their mid-20s, and one was due to a symptomatic tractional tear. These figures clearly indicate that patients with lattice degeneration in nonfellow eyes should not be treated unless symptoms occur. However, a discussion regarding self-examination of peripheral visual fields is in order to reduce chances of macular involvement by slowly progressive detachments due to round holes in lattice lesions.

 

 

FELLOW EYES

Lattice degeneration is three times more common in eyes in which a retinal detachment associated with lattice degeneration has occurred in the fellow eye than it is in the general population.[14] Lattice degeneration has been the most frequently studied indication for prophylactic therapy in fellow eyes. The widely quoted study of Folk et al[15] retrospectively studied 388 consecutive cases in which phakic retinal detachment associated with lattice degeneration occurred in one eye and lattice degeneration was present in the second eye. During an average follow-up period of over 7 years, new retinal breaks or detachments occurred in 31 (20%) of untreated eyes. New tears with retinal detachment developed in nine (5.9%), and new tears without detachment developed in 10 cases. In 10 eyes, new holes developed within areas of lattice degeneration, and atrophic retinal breaks occurred in areas distant from lattice lesions in the remaining two cases.

Folk et al[15] reported a reduction in the incidence of new retinal tears and detachments in eyes receiving prophylactic therapy of all lattice lesions. New tears without detachment occurred in five (3.0%) of these fully treated eyes. Retinal detachment occurred in three additional eyes (1.8%), compared to 5.9% in the 151 untreated phakic fellow eyes. The small beneficial effect of treating all lattice lesions was apparent when follow-up periods of 3, 5, and 7 years were analyzed separately. The beneficial effect was statistically significant for all patient subgroups, except in eyes with myopia of 6 D or more and in eyes with both high myopia and more than six clock hours of lattice degeneration. Importantly, in these subgroups, treatment did not reduce the risk of retinal tears or detachment. Conversely, no detachments occurred after full treatment in eyes with less than 6 clock hours of lattice degeneration or with less than 1.25 D of myopia.

In a subsequent evaluation of the same data, Folk et al[16] reported that new horseshoe tears developed in areas unassociated with lattice degeneration in ?30% of treated cases, and Byer[14] has estimated that as many as 58% of retinal detachments in eyes with lattice degeneration arise in areas that exhibit no visible vitreoretinal abnormalities. Because of this reality, some surgeons have recommended prophylactic therapy featuring the production of laser or cryotherapy burns over 360° of the peripheral retina. However, the precise indications, intraocular fidings, long-term results, and complications of this form of therapy have not been thoroughly described, and remarkably different success rates have been reported. Byer[14] has tabulated and reviewed data from 15 reports advocating such treatment, and he concluded that this form of treatment appeared to be both ineffective in preventing subsequent detachment and potentially dangerous in possibly aggravating vitreoretinal traction.

Studies of prophylactic therapy of lattice degeneration, with and without holes, in fellow eyes have been of limited value because they have not been prospective and because important information has been missing from available retrospective analyses. In particular, the outcomes have not been studied as a function of the presence of a PVD.

Appropriate prospective trials will be required to assess properly the value of treating lattice degeneration in fellow eyes. The relatively low incidence of retinal detachment in untreated cases, the frequency of new tears in normal-appearing retina, the apparent ineffectiveness of therapy in eyes with extensive lattice degeneration and high myopia, and the known success rate following treatment of symptomatic retinal tears and detachments indicate that prophylactic treatment is of limited value in these cases. The apparently modest treatment benefit following treatment of all lattice lesions in fellow eyes may be of value in selected patients, such as those with a poor surgical result in their first eye, or in patients who are incapable of recognizing symptoms of vitreous and/or retinal detachment or who live in areas with limited access to ophthalmologic care.

 

 

CYSTIC RETINAL TUFTS

Synonyms

  

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Retinal rosettes

  

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Granular patches

  

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Globules

Cystic retinal tufts are congenital lesions of the peripheral retina. They represent visible sites of abnormal vitreoretinal adhesions, and they therefore are potential causes of retinal tears and detachments following partial or complete PVD.

 

 

EPIDEMIOLOGY

Key Features

  

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Small (0.1-1.0 mm) sharply demarcated ovoid lesions

  

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Elevated whitish lesions associated with variable pigmentation

  

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Vitreoretinal traction upon the surface of the lesion

  

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Usually isolated

Cystic retinal tufts are present at birth.[17] They occur in 5% of adults and are unilateral in ?95% of cases. Cystic retinal tufts are equally distributed in all quadrants. About 80% of these tufts occur in the equatorial zone, and they are usually not present within the vitreous base.[17, 18]

 

 

PATHOGENESIS

Cystic retinal tufts are congenital focal malformations of the peripheral retina. The precise cause of these lesions is unknown.

 

 

CLINICAL FEATURES

Cystic retinal tufts appear as discrete, sharply circumscribed opaque white lesions in the peripheral retina (Figs 180.8 and 180.9).[18, 19] Pigment alterations in the base of the lesion are frequent, and there may be vitreous condensations attached to the surface.[17, 18] Cystic retinal tufts are not uncommonly associated with retinal breaks.[17-20] These breaks may be flap tears (Figs 180.10 and 180.11) or breaks with a free operculum (Fig. 180.12). Breaks with an operculum were more frequent than flap tears in an autopsy series.[20] These operculated tears may also occur in the absence of a PVD. In one autopsy study, 18% of retinal tears related to cystic retinal tufts were not associated with a PVD, and often there was a small asymptomatic area of surrounding retinal detachment.[20]

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FIGURE 180.8  Cystic retinal tuft in a 48-year-old woman.
From Byer NE: The peripheral retina in profile - a stereoscopic atlas. Torrance, CA: Criterion Press; 1952:21.

 

 

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FIGURE 180.9  Cystic retinal tuft in a 27-year-old woman, with a small atrophic retinal hole and a small localized area of subretinal fluid.
From Byer NE: The peripheral retina in profile - a stereoscopic atlas. Torrance, CA: Criterion Press; 1952:23.

 

 

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FIGURE 180.10  Cystic retinal tuft in a 68-year-old woman with acute symptomatic retinal tear, after PVD. Note the chalky-white lesion on the apex of the flap.
From Byer NE: The peripheral retina in profile - a stereoscopic atlas. Torrance, CA: Criterion Press; 1952:35.

 

 

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FIGURE 180.11  Cystic retinal tuft in a 58-year-old woman with a large acute symptomatic retinal tear, after PVD.
From Byer NE: The peripheral retina in profile - a stereoscopic atlas. Torrance, CA: Criterion Press; 1952:34.

 

 

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FIGURE 180.12  Cystic retinal tuft in a 26-year-old man, in whom the flap of a small retinal tear (which had been observed for 6 years without change) has now been avulsed as a free operculum.
From Byer NE: The peripheral retina in profile - a stereoscopic atlas. Torrance, CA: Criterion Press; 1952:25.

 

 

Retinal horseshoe tears associated with cystic tufts have been estimated to account for up to 10% of primary retinal detachments.[18, 19] In clinical studies, horseshoe tears are especially common as the result of traction on cystic retinal tufts after posterior vitreous separation. In a clinical study of 200 consecutive primary retinal detachments, cystic retinal tufts were associated with the only retinal break or a pathogenically important break in 13 eyes (6.5%).[18] A total of 16 retinal breaks were discovered, and 15 of 16 were horseshoe tears. In seven additional cases, cystic tufts were probably responsible for retinal breaks, although a greater percentage of these were holes with a free operculum.

In another report of 200 consecutive phakic nontraumatic retinal detachments, 15 (7.5%) were due to retinal tears associated with cystic retinal tufts.[19] Ten eyes had horseshoe tears and five had operculated breaks. Detachments due to operculated breaks progressed less rapidly and were less highly elevated.

Thus, 7-10% of retinal detachments are causally related to cystic retinal tufts because horseshoe tears and operculated holes occur at the site of these lesions. Cystic retinal tufts may also cause retinal detachment due to small atrophic holes from retinal thinning adjacent to the area of chronic vitreoretinal traction. However, the risk of retinal breaks associated with a cystic retinal tuft causing a clinically significant retinal detachment has been computed to be less than 0.3%.[18]

 

 

PATHOLOGY

Histologically, cystic retinal tufts are composed of degenerated retinal cells associated with variable degrees of glial proliferation. Larger tufts consistently show an absence of photoreceptor elements and prominent proliferation of glial cells. Vitreous strands attached to the tufts are often visible, and they ultrastructurally resemble the vitreoretinal junction found within the vitreous base.[17]

 

 

DIFFERENTIAL DIAGNOSIS

The fiding of a discrete characteristic lesion in the peripheral retina usually does not result in diagnostic difficulties. The slightly elevated tufts are occasionally interpreted as retinal flaps associated with tears, but the tufts are much more opaque than normal retinal tissue. Most other focal congenital lesions of the peripheral retina are located within the vitreous base near the ora serrata.

 

 

TREATMENT

As mentioned above, the chances of retinal detachment from a cystic retinal tuft have been estimated at ?0.3%. Thus they should not be considered for prophylactic therapy. Since they are usually unilateral, treatment of a fellow eye is not a consideration.

 

 

ASYMPTOMATIC RETINAL BREAKS

Synonyms

  

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Retinal flap 'horseshoe' tear

  

.   

Retinal operculated tear

  

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Retinal hole

A retinal break is a full-thickness discontinuity of retinal tissue, most frequently occurring in the retinal periphery or mid-periphery. Retinal breaks are the most important precursor of RRD, because they are necessary to permit passage of liquid vitreous into the subretinal space. However, most retinal breaks do not cause retinal detachment. Retinal breaks are defied as 'symptomatic' if they occur in association with symptoms of a PVD and are due to vitreoretinal traction. Asymptomatic breaks are usually discovered during retinal examinations.

 

 

EPIDEMIOLOGY

Key Features

  

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Retinal flap 'horsehoe' tears are associated with persistent vitreoretinal traction upon a portion of the disrupted retina

  

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Operculated tears occur when a piece of retina is completely separated, by vitreoretinal traction, from the surrounding retina

  

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Retinal holes are usually due to atrophic changes in the retina, and they are not associated with vitreoretinal traction

Both autopsy and clinical studies have documented the important fact that the vast majority of asymptomatic retinal breaks are not associated with clinical retinal detachment. Most retinal breaks causing retinal detachment are due to flap tears associated with some degree of PVD, although a significant percentage are due to atrophic retinal holes in lattice degeneration (see Chapter 182).

AUTOPSY STUDIES

These have documented the presence of retinal breaks in 4-8.7% of eyes, with an average of 5.8%.[21] Foos[20, 22] further clarified the prevalence in a study of 4812 autopsy eyes. He classified retinal breaks into (1) retinal tears caused by vitreous traction and (2) round holes without signs of previous vitreous traction. Retinal tears were characterized by the presence of an anterior flap or an overlying operculum.

Foos[20] identified 148 full-thickness retinal tears in 89 (1.9%) of 4812 eyes. The tears were bilateral in nine cases, making the incidence of retinal tears 3.3% in the 2406 patients. Six percent of the tears were within the vitreous base and were related to small anterior zonular-traction tufts. Nine such breaks were present in nine eyes, and only one of these eyes had a PVD. Seven of the nine breaks associated with zonular-traction tufts were operculated and two were flap tears. The remaining 94% of the retinal tears were due to vitreoretinal traction. Sixty-four percent of the 139 tears were flap tears and 36% were operculated. In three eyes (3.4%) with flap tears, no PVD was present. Cystic retinal tufts were present in the flap of two of these three tears, and the third tear was behind an enclosed oral bay. There was no PVD in nine eyes (18%) with operculated tears. A cystic retinal tuft was present in the operculum in each of these cases. Eighty (54%) of the retinal breaks caused by vitreous traction in this series were in the inferior quadrants and 68 (46%) in the superior quadrants. The temporal quadrants were involved most frequently.

Retinal tears appeared in the third decade of life and the incidence increased with advancing age. Horseshoe tears were especially frequent in older patients, corresponding to an increased prevalence of posterior vitreous separation (Fig. 180.13). Lattice degeneration was present in 5.4% of all eyes and in 17% of eyes with retinal tears. However, only six (21%) of 29 retinal tears in eyes with lattice degeneration involved a lattice lesion.

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FIGURE 180.13  Retinal horseshoe tear causes retinal detachment. Focal vitreoretinal traction is seen pulling the flap of the tear up and to the left. Fluid vitreous has seeped through the tear into the subretinal space, elevating the retina into a bullous detachment.

 

 

In a subsequent study, Foos[22] described the prevalence of retinal holes in an expanded series of 5600 consecutive autopsy eyes. These retinal breaks, which were not due to vitreoretinal traction, were observed in 136 eyes (2.4%). They were bilateral in 23% of cases and occurred in 4% of patients. In only eight (5.9%) of the 136 eyes were the retinal breaks not associated with other abnormalities. These eight eyes, all in elderly patients, had unilateral, single, small breaks within the vitreous base.

Secondary retinal holes were present in 128 (2.3%) of the 5600 eyes.[22] These holes were associated with lattice degeneration in 103 (80%) of the 128 eyes. They were associated with zonular-traction tufts in 10 eyes, previous chorioretinitis in nine, meridional folds in three, and paving stone degeneration in two. A single hole was associated with 'miscellaneous' additional fidings. The prevalence of these retinal breaks was the same in phakic and aphakic eyes.

 

 

CLINICAL STUDIES

The largest clinical series evaluating the prevalence of asymptomatic retinal breaks are those of Byer.[20, 23, 24] In a consecutive series of 1700 patients 10 years of age or older who were not referred by other ophthalmologists, asymptomatic retinal breaks were discovered in 111 (3.3%) of 3400 eyes. There were 156 breaks in the 111 affected eyes. The incidence of retinal breaks increased with advancing age and was 6.9% in patients 40 years of age or older. Patients with retinal breaks tended to be more myopic than the total patient group. Horseshoe tears accounted for 10%, round holes with an operculum for 13%, and round holes without an operculum for 76% of the breaks. Breaks with an operculum were slightly more common in patients over age 40, and 81% of the horseshoe tears occurred in this same age group.

In the studies of Byer,[20, 23, 24] retinal breaks were most frequent in the inferotemporal quadrant, followed by the superotemporal quadrant. Eight of 16 horseshoe tears occurred in the superonasal quadrant. The anteroposterior distribution of the retinal breaks ranged from the ora serrata to just posterior to the equator, and they were most common just posterior to a point midway between the equator and the ora serrata. Focal retinal detachments associated with retinal breaks were present in 76% of the 111 eyes. Fifty-five percent of the retinal breaks were directly associated with areas of lattice degeneration.

Byer[24] studied the natural course of asymptomatic retinal breaks in 196 consecutive patients. There were 359 retinal breaks in 231 eyes; 77% were round atrophic holes, 14% were horseshoe tears, and the others were tears with an overlying operculum. Forty-one percent occurred in the upper quadrants and 59% in the lower quadrants. Eighteen areas of subclinical retinal detachment extending 1-2 disk diameters posterior to the equator were discovered in 17 eyes of 15 patients in the series. Of the subclinical detachments, 39% were in the superior quadrants and 61% in the inferior quadrants. Fifteen (83%) of the 18 areas of detachment were caused by atrophic holes and round holes within lattice degeneration. There was a significant tendency for subclinical detachments to occur in eyes with more than 3 D of myopia.

Lattice degeneration was present in 65% of the 231 eyes with retinal breaks.[24] A total of 261 breaks occurred in the eyes with lattice degeneration and 230 (88%) were within or adjacent to the lattice lesions. However, only four horseshoe tears occurred adjacent to lattice lesions, whereas 15 occurred in other areas in the eyes with lattice degeneration.

Hyams and Neumann[25] discovered retinal breaks in 37 (11%) of 332 asymptomatic myopic eyes. Forty-eight retinal breaks were discovered in 34 patients. Thirteen (27%) of the breaks were horseshoe tears, nine (19%) were round tears with an operculum, and the remainder were atrophic round holes. The prevalence of retinal breaks was related to patient age. Breaks occurred in 6.4% of patients aged 10-20 and in 17% of 118 patients aged 41 years or older. There was no statistically significant association between the incidence of retinal breaks and the degree of myopia. In this study, 11 (85%) of 13 horseshoe tears were in the superior quadrants. All operculated retinal holes were in the superior quadrants, and seven of nine were in the superotemporal quadrant. Twenty-five of 26 atrophic holes were in the temporal quadrants.

Clinical data from these two large studies are thus consistent with the fidings in autopsy studies. Asymptomatic retinal breaks are present in ?6% of eyes in the general population. Round atrophic holes are substantially more common than holes or tears due to vitreoretinal traction, but a significant number of horseshoe tears in the superior quadrants are observed in asymptomatic eyes. This fiding is notable because breaks of this type are thought to be a frequent cause of progressive retinal detachment.

 

 

PATHOGENESIS

Retinal tears are by defiition secondary to vitreoretinal traction. Focal sites of traction may be visible (lattice degeneration, cystic retinal tuft) or invisible, in which case they cannot be detected until a tear forms at the site. Tears usually occur when the vitreous cortex separates from the retina at the site of a vitreoretinal adhesion, and this usually occurs suddenly during a progressive PVD. If the focal adhesion between cortical vitreous and retina is stronger than the bond between sensory retina and retinal pigment epithelium, a tear will occur. If the vitreoretinal traction remains attached to an edge of the tear, a flap or 'horseshoe' configuration will be observed. If the traction pulls a piece of tissue completely away from the retina, an operculated tears will result. Sometimes, flap tears become operculated over time.

Atrophic retinal breaks are categorized as 'holes' and are usually due to degenerative changes within the retina. They are most important in association with lattice degeneration, because persistent vitreoretinal traction upon the edges of lattice lesions can result in their becoming causes of retinal detachment.

 

 

CLINICAL FEATURES

Retinal breaks are important because of their potential to cause rhegmatogenous retinal detachment. Both atrophic holes and operculated tears that are unassociated with vitreoretinal traction in their vicinity are very unusual causes of subsequent retinal detachment. In addition, flap tears that are discovered in patients that do not have symptoms of PVD are not common causes of later retinal detachment. These points are particularly true if aphakic eyes and the fellow eyes of patients with previous detachment are excluded.[24, 26] Byer[24] studied the natural course of 359 asymptomatic retinal breaks observed in 231 eyes of 196 patients. The characteristics of these breaks were described previously. No cases of clinical retinal detachment occurred during a follow-up interval averaging several years. Three of 18 subclinical detachments demonstrated enlargement. In phakic eyes of patients without a history of retinal detachment in the fellow eye, asymptomatic focal detachments also have a low risk of progressing to clinical significance.

Davis[26] also studied the natural course of asymptomatic retinal breaks. In this study, 80% of the breaks were in the fellow eyes of patients with previous retinal detachment. Thirty-one percent of 16 phakic eyes with asymptomatic subclinical detachments developed a clinically significant detachment, but only 5% of 111 eyes with retinal breaks unassociated with subclinical detachment progressed to clinical detachment. Therefore, fellow eyes appear to have a different prognosis in patients with a history of retinal detachment than in those with no such history.

Neumann and Hyams[27] also suggested that it is rare for nonacute retinal breaks to cause later clinical retinal detachment. The most frequent exception is retinal detachment associated with atrophic holes within lattice degeneration.[28, 29] However, this occurs in less than 1% of cases with lattice degeneration and atrophic holes, and it is most common in patients younger than age 40.[5]

 

 

PATHOLOGY

By defiition, retinal breaks are foci of full-thickness discontinuity of the sensory retina.

Retinal tears are associated with adhesions between overlying cortical vitreous and the retina. If a portion of the edge of the break remains attached to vitreous, a horseshoe configuration results. If a piece of full-thickness retina is pulled entirely out the surrounding retina, an operculated tear is observed. Atrophic retina holes are not associated with vitreoretinal adhesions.

 

 

DIFFERENTIAL DIAGNOSIS

Retinal breaks are usually located peripherally, and some degree of expertise with indirect ophthalmoscopy and scleral depression is required to visualize them. Assuming that the lesions can be detected, they are infrequently confused with other focal lesions. However, vitreoretinal adhesions can be very difficult to visualize, and it may be impossible to be certain that no vitreoretinal traction persists in the vicinity of some breaks.

 

 

TREATMENT

In phakic nonfellow eyes, asymptomatic retinal breaks that are routinely discovered during an evaluation of the peripheral retina are extremely unlikely to lead to clinical retinal detachment, even if they are flap tears and even if PVD occurs.[30] During a follow-up period averaging 11 years, asymptomatic retinal breaks in 235 eyes of 196 patients were studied, and horseshoe-shaped tears were present in 45 cases. Acute PVD occurred in nine eyes without adversely affecting the preexisting breaks, although new horseshoe-shaped tears developed in three cases, and these were promptly treated. Subclinical retinal detachments were observed in 19 (8%) eyes. Modest extension of subretinal fluid required therapy in two of these cases, and in a third case a peripheral clinical retinal detachment slowly developed after 14 years of observation.

Prophylactic therapy for asymptomatic retinal breaks in phakic nonfellow eyes is usually not recommended. An occasionally observed exception to this rule is an inferior retinal dialysis. These breaks can cause slowly progressive retinal detachments that frequently become symptomatic only after macular involvement.[31]

Asymptomatic retinal breaks in nonfellow, nonphakic eyes or eyes undergoing cataract surgery have sometimes been regarded as an indication for prophylactic therapy. However, Friedman et al[32] followed 18 retinal breaks in nonmyopic aphakic eyes for 3-7 years, and none detached. Hyams et al[33] studied 103 myopic aphakic eyes and discovered 25 asymptomatic retinal breaks in 19 eyes. Although six of the 25 were horseshoe-shaped tears, later retinal detachment occurred in no cases. Still, treatment of horseshoe-shaped tears in these cases appears to be frequently recommended despite the lack of appropriate information in the literature.[7, 22]

Asymptomatic retinal breaks in phakic second eyes of patients with previous retinal detachment are frequently cited as an indication for prophylactic therapy. Flap tears may be more likely to cause retinal detachment than round or operculated retinal holes. However, Hyams et al[33] followed 10 untreated asymptomatic horseshoe-shaped tears in phakic fellow eyes, and no retinal detachments occurred. Deficiencies in prior reports have made it difficult to assess both the natural course of asymptomatic retinal breaks that are discovered on an examination of a fellow eye and the results of treatment of these lesions. Most of these breaks are round and located within areas of lattice degeneration, and these cases were discussed earlier. Data regarding therapy for asymptomatic horseshoe-shaped tears in fellow eyes suffer from a lack of details, including the status of the vitreous gel and the relationship between the original retinal break and the cause of subsequent retinal detachment. An aggressive national program of routine treatment of all retinal breaks in fellow eyes did not reduce the prevalence of retinal detachment in Israel.[9] Still, treatment of horseshoe-shaped tears that are discovered in asymptomatic fellow eyes is sometimes recommended despite the absence of optimal supportive data.[34, 35]

 

 

ADDITIONAL SELECTED PERIPHERAL VITREORETINAL PATHOLOGY

Three additional peripheral retinal abnormalities are worthy of brief discussions, because they are common and occasionally misinterpreted as being of significance. These include peripheral cystoid degeneration, paving stone degeneration, and 'white without pressure'.

 

 

PERIPHERAL CYSTOID DEGENERATION

Peripheral cystoid degeneration is a process characterized by clusters of many tiny intraretinal spaces located immediately posterior to the ora serrata.[3, 36] This appears to be a degenerative condition involving primarily the middle retinal layers 'typical' or inner retinal layers 'reticular', although the two forms are not distinguishable on clinical examination.[37] The cystoid zones have their broad bases located against the ora serrata and extend posteriorly and circumferentially in a variety of shapes, forming a ring-like 'band' in the far peripheral retina. Involvement tends to be more prominent temporally than nasally and superiorly than inferiorly. It has been seen histologically in a child as young as 6 days of age, and by the age of 8 years, it is present in all eyes.[3, 36] There is a progressive increase in severity up to the seventh decade of life.

Clinically, most cases of peripheral cystoid degeneration are unrecognized because of its ophthalmoscopic subtlety. With scleral depression, small, smoothly elevated, sometimes stippled areas of the inner retinal surface of these lesions can frequently be observed in the far anterior retinal periphery. It is sometimes impossible to differentiate from early small lesions of senile retinoschisis.

The extent of peripheral cystoid degeneration is unrelated to the axial length of the eye.[3] It is associated with no other vitreoretinal abnormalities except retinoschisis, a topic that is discussed in Chapter 181. PVD, even when it extends more anterior than the posterior limits of peripheral cystoid degeneration, does not show any apparent increased deleterious effects on these areas, and retina involved with peripheral cystoid degeneration does not appear to be more friable or more subject to retinal tears.[3]

 

 

PAVING STONE DEGENERATION

Paving stone degeneration is characterized by prominent, discrete, rounded, yellow-white lesions between the ora serrata and the equator, numbering from one to several dozen (Fig. 180.14).[3, 38] They vary in size from 0.1 to 1.5 mm in diameter, but multiple adjacent lesions may coalesce into muchlarger lesions. The distinctive yellow-white color is caused by the relatively unobstructed view of the inner surface of the sclera, which may also reveal several large choroidal vessels. Lesions frequently have prominent pigment borders, and pigmented septa may intersect adjacent lesions.[3]

Click to view full size figure  

 

FIGURE 180.14  Paving stone degeneration.

 

 

Histologically, lesions are sharply circumscribed zones of retinal thinning caused by loss of rods and cones, outer plexiform and outer nuclear layers.[3, 38] The pigment epithelium is absent, and there is variable loss of the choriocapillaris. The overlying vitreous is unchanged in the involved areas. Lesions show no apparent increase in glial cells and are not associated with the presence of inflammatory cells.

Paving stone lesions appear in ?22% of adults and are bilateral in ?40% of involved patients.[3, 38] The lesions tend to be bilaterally symmetric and become more extensive with increasing age. Lesions are most prevalent inferiorly, and more than 50% of lesions are located between the 5 o'clock and the 7 o'clock meridians. The area of the nasal horizontal meridian tends to be spared. Although not statistically proved, there is suggestive evidence that highly myopic eyes may have more extensive involvement.[3]

Paving stone degeneration presents no threat to vision and therefore is not considered for prophylactic treatment. When found in eyes in which later retinal detachment occurs, the paving stone lesions generally provide an effective barrier to extension of the detachment. Rarely, retinal breaks can occur at the edges of the paving stone lesions. In addition, the retina may detach over these lesions, and circumscribed reddish areas corresponding to the location of the paving stone lesions, may appear as pseudoholes.

 

 

WHITE WITHOUT PRESSURE

'White without pressure' is one of the most enigmatic of the visible peripheral vitreoretinal abnormalities. The term refers to geographic areas of relative whiteness of the peripheral retina (Fig. 180.15). When this can be seen by indirect ophthalmoscopy without scleral depression, it is called 'white without pressure'. White areas visible only with scleral depression are called 'white with pressure'. White without pressure is regarded by some as an exaggerated or advanced form of white with pressure.

Click to view full size figure  

 

FIGURE 180.15  White-with-pressure phenomenon.
From Byer NE: The peripheral retina in profile - a stereoscopic atlas. Torrance, CA: Criterion Press; 1952:135.

 

 

These areas tend to be circumferentially oriented. The ends and posterior boundaries are irregular and sharply defied, whereas the anterior limits are less precise. Areas of white without pressure occasionally extend posterior to the equator and can extend back to the temporal vascular arcades. White with and without pressure is most important as an entity that can mimic a shallow retinal detachment or retinoschisis, particularly to relatively inexperienced observers. There may be normal, darker-appearing areas within larger areas of white without pressure, and these may be mistaken for retinal breaks.[39]White without pressure is more frequent in the temporal quadrants, especially the inferotemporal quadrant.

White without pressure is considerably more common in heavily pigmented patients than in white patients. Hunter[40] discovered white without pressure in 2.5% of 692 consecutive unselected white patients and in 23% of 308 similar black patients. Karlin[41] noted that white without pressure was nine times more common in blacks than in whites.

It also is more common in young patients and in myopic eyes.

The cause of white without pressure is unknown. Dobbie[42] reported a patient with geographic areas of white without pressure extending into the posterior pole. Clinical and fluorescein angiographic study of these areas revealed no other abnormalities. The eye was examined by light and electron microscopy after the patient's death, and no abnormalities were found. Many authors consider white without pressure as simply an abnormal light reflex originating at the vitreoretinal interface without structural abnormalities.[43] This theory is in keeping with the absence of consistent abnormalities demonstrable by light or electron microscopy. Other evidence suggesting that white without pressure is due only to an abnormal light reflex include the observations that these areas migrate and/or disappear and are far more frequent in young patients. Accentuated light reflexes are also common in children and young adults when fundus photographs are taken of the posterior pole.

 

 

CONCLUSION

The peripheral retina contains many focal changes that vary from insignificant congenital variations to sight-threatening retinal tears. Fortunately, there are sufficient data on this topic to allow an experienced observer to distinguish important lesions from those that pose no threat to vision. It is critical that individuals interested in the peripheral retina become skilled in the use of indirect ophthalmoscopy, scleral depression, and accessory contact lenses.

 

 

REFERENCES

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19. Murakami-Nagasako F, Ohba N: Phakic retinal detachment associated with cystic retinal tuft.  Graefes Arch Clin Exp Ophthalmol  1982; 219:188-192.

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24. Byer NE: The natural history of asymptomatic retinal breaks.  Ophthalmology  1982; 89:1033-1039.

25. Hyams SW, Neumann E: Peripheral retina in myopia; with particular reference to retinal breaks.  Br J Ophthalmol  1969; 53:300-306.

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28. Morse PH: Lattice degeneration of the retina and retinal detachment.  Am J Ophthalmol  1974; 78:930-934.

29. Tillery WV, Lucier AC: Round atrophic holes in lattice degeneration - an important cause of phakic retinal detachment.  Trans Am Acad Ophthalmol Otolaryngol  1976; 81:509-518.

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31. Sigelman J: Vitreous base classification of retinal tears: clinical application.  Surv Ophthalmol  1980; 25:59-74.

32. Friedman Z, Neumann E, Hyams SW: Vitreous and peripheral retina in aphakia: a study of 200 non-myopic aphakic eyes.  Br J Ophthalmol  1973; 57:52-57.

33. Hyams SW, Neumann E, Friedman Z: Myopia-aphakia. II. Vitreous and peripheral retina.  Br J Ophthalmol  1975; 59:483-485.

34. American Academy of Ophthalmology: Management of posterior vitreous detachment, retinal breaks, and lattice degeneration. Preferred practice pattern,  San Francisco, American Academy of Ophthalmology, 1998.

35. Wilkinson CP: Evidence-based analysis of prophylactic treatment of asymptomatic retinal breaks and lattice degeneration.  Ophthalmology  2000; 107:12-15.

36. O'Malley PF, Allen RA: Peripheral cystoid degeneration of the retina.  Arch Ophthalmol  1967; 77:769-776.

37. Foos RY: Senile retinoschisis - relationship to cystoid degeneration.  Trans Am Acad Ophthalmol Otolaryngol  1970; 74:33-50.

38. O'Malley PF, Allen RA, Straatsma BR, O'Malley CC: Paving-stone degeneration of the retina.  Arch Ophthalmol  1965; 73:169-182.

39. Curtin BJ: The myopias,  New York: Harper & Row; 1985:339.

40. Hunter JE: Retinal white without pressure: review and relative incidence.  Am J Optom Physiol Opt  1982; 59:293-296.

41. Karlin DB: Discussion of Karlin DB, Curtin BJ: axial length measurements and peripheral fundus changes in the myopic eye.   In: Pruett RC, Regan CD, ed. Retina congress,  New York: Appleton-Century-Crofts; 1972:641.

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