30 I: Principles
that 0.2% had retinal detachment. If such a study were continued for 50 years, a prevalence of 2% could be expected.
EPIDEMIOLOGY OF RETINAL DETACHMENT
Reliable information regarding the incidence and prevalence of retinal detachment is difficult to find because of the mobility of today’s population. Several epidemiologic studies of relatively confined groups reveal an annual incidence of about one retinal detachment in 10,000. Assuming an average life expectancy of 74 years, the prevalence is approximately 0.7%.
The most common features associated with retinal detachment are myopia, pseudophakia, lattice degeneration, and trauma. Approximately 40% to 55% of all detachment patients have myopia, and the amount of myopia is directly related to the likelihood of detachment. Twenty to thirty percent of retinal detachments are associated with lattice degeneration, and in 10% to 20%, the eyes have suffered direct ocular trauma. Approximately 30% to 40% of detachments are associated with a history of cataract surgery, and detachment is more likely if the vitreous gel has been involved by surgical complications or Nd:YAG capsulotomy.
Traumatic detachments are most common in youth, myopic detachments occur most frequently among people older than 25, and the incidence of pseudophakic detachments rises with each decade of advancing age (Figure 2–22). The risk factors are not mutually exclusive, and highly myopic eyes with lattice degeneration that undergo cataract surgery appear to be at relatively high risk.
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90 |
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Trauma |
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80 |
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Retrolental fibroplasia |
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Inferior temporal dialysis |
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70 |
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Myopia |
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Aphakia |
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60 |
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frequency |
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40 |
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Relative |
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30 |
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Age (years)
Figure 2–22. Age distribution of five types of retinal detachment. (Redrawn with permission from S. Karger AG, Basel, from Hilton GF, Norton EWD: Juvenile retinal detachment. Mod Probl Ophthalmol 1969;8:325–341.)
2: Pathogenesis, Epidemiology, and Natural Course |
31 |
VARIABLES REGARDING EPIDEMIOLOGY
Age
The most common ages for retinal detachment are between 40 and 80 years, although there is a small increase in rate due to trauma or hereditary factors in the teens (Figure 2–23). In rare instances, detachment is discovered in a newborn, and occasionally it occurs as late as the ninth or tenth decade of life.
Sex
Approximately 60% of detachments occur in males. The incidence remains higher for males even when data are corrected for ocular trauma, which is much more common among males than females.
Race
The incidence of detachment is reported to be relatively high among Asians and Jews, and relatively low among people of African descent. One study of Native Americans revealed an incidence essentially equal to that of Caucasians.
Heredity
Primarily because myopia and lattice degeneration have hereditary tendencies, retinal detachment also has some hereditary predisposition. A positive family history of retinal detachment is a relevant risk factor, but most cases are sporadic.
Bilaterality
Approximately 15% of detachment patients ultimately develop detachment in the second eye. The effect on bilaterality of prophylactic treatment, such as cryopexy of retinal breaks in the second eye at the time of detachment in the first eye, has not
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Aphakia |
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Figure 2–23. Age distribution of retinal detachment patients with small juvenile mode and prominent middle-age mode. (Redrawn with permission of S. Karger AG, Basel, from Hilton GF, Norton EWD: Juvenile retinal detachment. Mod Probl Ophthalmol 1969;8:325–341.)
32 I: Principles
been optimally evaluated. Bilateral detachments are more common in pseudophakic patients, with an incidence as high as 25% to 30%.
SYSTEMIC AND GENETIC CONDITIONS ASSOCIATED WITH RETINAL DETACHMENT
Rhegmatogenous detachments can result from retinal breaks associated with Marfan syndrome, Ehlers-Danlos syndrome, Wagner’s vitreoretinal degeneration, Stickler syndrome, Pierre Robin syndrome, familial exudative vitreoretinopathy, juvenile retinoschisis, proliferative diabetic retinopathy, proliferative sickle retinopathy, retinopathy of prematurity, atopic dermatitis, acute retinal necrosis, and cytomegalovirus virus retinitis.
CLASSIFICATION OF RETINAL DETACHMENTS
Retinal detachments may be classified according to a variety of morphologic findings (Table 2–4). There may be considerable overlap in some of these categories,
Table 2–4. Classification of Detachment
Morphology of Break |
Size of Break |
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Horseshoe |
Small |
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Round or oval |
Moderate |
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Operculated |
Large |
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Atrophic |
Giant |
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Dialysis |
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Irregular |
Extent of detachment |
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Etiology of break |
One quadrant or less |
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Two quadrants |
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Traditional |
Three quadrants |
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Horseshoe |
Four quadrants |
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Operculated |
Total |
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Atrophic |
Detachment of pars plana |
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Postnecrotic |
epithelium |
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Location of break |
Secondary changes |
Near ora serrata Equatorial zone
Posterior to equatorial zone Macular
Number of break(s)
Single
Multiple
Macular status
Attached
Detached
Demarcation lines Pigmented Nonpigmented
Intraretinal macrocysts Linear and angular strands on
outer surface of detached retina (retina fibrosis)
Microcystic degeneration of retina Thinning of retina
Macular edema Macular hole
Proliferative vitreoretinopathy (PVR)
2: Pathogenesis, Epidemiology, and Natural Course |
33 |
as a variety of retinal breaks can coexist in the same case. Atypical rhegmatogenous retinal detachments are commonly seen in eyes with proliferative diabetic retinopathy.
PATHOLOGY OF THE DETACHED RETINA
The outer layers of the detached retina undergo the greatest alteration due to separation from the blood supply of the choriocapillaris. Experimental work with the owl monkey has revealed degenerative changes in the outer segments of the receptor cells within a few days after detachment. The discs of the outer segments become ruptured and disorganized and, in time, assume bizarre shapes. In the normal retina, shed fragments of photoreceptor outer segments are phagocytosed by the retinal pigment epithelium. These lamellar inclusion bodies are referred to as phagosomes.
In retinal detachment, this process is disrupted so that phagosomes disappear from the retinal pigment epithelium. Both proliferative and degenerative changes occur in the retinal pigment epithelium. Changes visible with an electron microscope include migration of the pigment granules from the anterior processes of the retinal pigment epithelial cells posteriorly and thickening of Bruch’s membrane. After surgical reattachment, the receptor cell outer segments regenerate, the discs assume a more normal pattern, and phagosomes reappear in the retinal pigment epithelial cells.
With long-standing detachments, the inner and outer nuclear layers of the detached retina undergo degeneration, become thinner, and may ultimately fuse into one layer. Although the inner retina is well preserved initially, the ganglion cells decrease in number in long-standing detachments and may eventually disappear. Other chronic changes include hyalinization of both retinal vessels and the choriocapillaris. Additional pathologic findings in eyes with chronic retinal detachments include proliferative vitreoretinopathy, intraretinal macrocysts, and demarcation lines.
PROLIFERATIVE VITREORETINOPATHY
The most ominous and clinically significant finding in retinal detachment is the presence of proliferative vitreoretinopathy (PVR), the process that is responsible for the vast majority of surgical failures of retinal reattachment surgery. The consequence of cell migration and elaboration of collagen is the formation of membranes involving the inner and outer surfaces of the retina, as well as the vitreous. In time, and under the influence of mediators of inflammation, the membranes contract, distorting the retina into folds (Figure 2–24). Localized contracture in the periphery is referred to as a star fold (Figure 2–25), and a similar process in the posterior pole is referred to as a macular pucker (Figure 2–26). Two more recent classification systems for PVR have come into use and, though imperfect, they have improved our evaluation of retinal detachment and its therapy (see Chapter 5, page 104).
Figure 2–24. Total retinal detachment associated with proliferative vitreoretinopathy (PVR). The retina is pulled into fixed folds by the membranes on the surface of the retina.
Figure 2–25. A star fold located temporal to the macula is due to localized epiretinal membranes that cause surface traction on the detached retina.
Figure 2–26. A “macular pucker” (or “epimacular proliferation”) is due to an epiretinal membrane localized to the central area of the retina.
2: Pathogenesis, Epidemiology, and Natural Course |
35 |
INTRARETINAL MACROCYSTS
Large intraretinal cystoid spaces may develop over many months in long-standing retinal detachments (Figure 2–27). They may develop in the posterior pole but are more frequent in the equatorial zone. Retinal detachments caused by inferior retinal breaks, such as the classic inferior temporal dialysis of the young, are generally slow in their progression and thus may be present long enough to develop
A
B
Figure 2–27. Intraretinal cysts are a sign of chronic retinal detachment. (A) A large intraretinal cyst in detached retina. (B) Following reattachment, the cyst has spontaneously resolved.