Clinical background

Retinal detachment (RD) is a physical separation of the neural retina from the retinal pigmented epithelium (RPE). An important physiological ramification of the creation of a detachment is an increase in the physical distance between the photoreceptor cells and their blood supply, the choroicapillaris. Detachment recreates a space that disappears during early embryonic development.

Definitions: types of retinal detachment

Detachment occurs in three categories: exudative (or serous), traction, and rhegmatogenous ( Box 71.1 ).

Box 71.1

Rhegma, derived from Greek, refers to a break in continuity

Serous detachment

Serous detachment occurs as fluid accumulates between the neural retina and RPE, but the retina remains physically intact. Serous detachments may be idiopathic or occur as part of inflammatory reaction, or as a result of neoplastic ocular tumors ( Box 71.2 ).

Box 71.2

Central serous retinopathy (CSR) or central serous choreoretinopathy results from serous detachment of the macula. It occurs most commonly in middle-aged males. The mechanisms are poorly understood. These detachments usually, but not always, resolve spontaneously. Even those that do resolve can have lasting effects on vision

Tractional detachment

Tractional detachment occurs as a result of “vitreoretinal adhesions” or the growth of cells in the vitreous that attach to the surface of the retina and contract, mechanically creating an RD.

Rhegmatogenous detachment

This is the commonest form of RD and the focus of this chapter. It results from a tear across the retina, creating a physical continuity between the vitreous and RPE–photoreceptor interface and thus resulting in the accumulation of “foreign” fluid beneath the retina and a subsequent detachment ( Figure 71.1 ).

In a rhegmatogenous detachment a tear or break forms in the retina, allowing fluid from the vitreous cavity to enter, and creating a space between the neural retina and retinal pigmented epithelium (RPE). A laser can be used to “seal” the retinal tear and encircling bands of material (scleral buckle) can be used to indent the wall of the eye so that the retina is reapposed to RPE. Natural adhesion forces will allow reattachment to occur. A rhegmatogenous detachment may detach the whole retina. A serious complication of reattachment is the formation and attachment of scar tissue on the vitreal surface of the retina, which can become contractile and subsequently create a traction detachment.

Tractional detachments can also be rhegmatogenous, i.e., a complex form of RD ( Figure 71.2 ). These often result from fibrotic or scar tissue that forms on either surface of the retina after reattachment. Contraction of this scar tissue can cause traction on the retina with wrinkling and redetachment and often retearing of a previous break or creation of new ones. This is a visually devastating condition and its prevalence has remained discouragingly static over the years.

Rhegmatogenous detachments can be created in animal models by the injection of fluid between the neural retina and underlying retinal pigmented epithelium. The pipette or needle will leave a hole in the retina that will remain open and even expand, creating the retinal break characteristic of this type of detachment.

Symptoms, signs of retinal detachment, and diagnostics

All RDs are accompanied by some loss of visual function but this will vary depending upon the type of detachment, its size, and retinal location, making it difficult to ascribe one set of symptoms to the condition ( Box 71.3 ). Diagnosing RD is complex, with many qualifications.

Abnormal vision is the only reliable symptom of RD. But the types of abnormal vision are large and varied: light flashes, floaters, changes in the peripheral visual field, decreased acuity, defective color vision, distorted vision (metamorphopsia), or even unilateral double vision (diplopia). Patients often remain unaware of large peripheral detachments until they approach the macula and begin to produce a visual field defect. Many times they are discovered during an ocular examination. Foveal detachment always involves loss of central visual acuity. Indeed, the duration of a foveal rhegmatogenous RD is based upon the time of patient-observed decrease in visual acuity. A macular rhegmatogenous RD will generally produce visual acuity loss that cannot be corrected, while blurred vision produced by a centrally located serous detachment (central serous retinopathy, or CSR) can often be corrected by shifting the focal plane of the image to a more forward location. The book series Retina includes much information relevant to diagnosing detachments.

History

Greg Joseph Beer provided what is generally described as the earliest description of detachment in the early 18th century ; his observations were done without benefit of an ophthalmoscope (an instrument with magnifying lenses that allows examination of the inside of the eye). After Hermann von Helmholtz recognized the importance of the ophthalmoscope in about 1850, detailed descriptions of detachments and accompanying breaks or tears proliferated rapidly.

The first treatment of rhegmatogenous RD by sealing the retinal break with a red-hot probe occurred in 1889, and was revived as a standard treatment by Jules Gonin. Gonin was also the first to suggest a relationship between detachment duration and successful visual recovery. His technique is credited with moving an inevitably blinding condition into a treatable one. The next major advance occurred 70 years later when Custodis described the “scleral buckle” ( Box 71.4 ).

This technique achieved a success rate of between 75 and 88%. In the early 1970s Norton described the use of “pneumatic retinopexy,” or injection of an expanding gas bubble into the vitreous cavity ( Box 71.5 ) to reappose the retina and RPE (once these tissues are moved into close physical proximity, natural adhesive forces will usually cause them to reattach ). There is still much ongoing discussion on the use of scleral buckling, primary vitrectromy, and pneumatic retinopexy to treat rhegmatogenous RD.

The success rate for rhegmatogenous RD after one surgical procedure is now cited as in the range of 80–95%. That number rises closer to 95% if a second reattachment procedure is performed.

Surgical success refers to a reapposition of the sensory retina and RPE and does not refer specifically to the return of vision. Redetachment by traction on the retina and imper fect vision can both occur after successful reattachment. The goal of experimental detachment in animal models is gaining an understanding of underlying cellular mechanisms that will presumably aid in developing improvements in the treatment of the primary detachment as well as the means for preventing the occurrence of secondary tractional RD.

Epidemiology

The incidence of rhegmatogenous RD is described as anywhere from 1 in 10 000 to 1 in 15 000 in the general population. This translates to a prevalence of about 0.3% or approximately 1 in 300 patients over the course of the average patient lifetime. The risk levels for RD vary slightly among different studies but there is general agreement that if ocular trauma is factored out, the prevalence among men and women is about equivalent.

Prognosis and complications

Rhegmatogenous RD is still the condition most frequently treated by retinal surgeons (H. Heimann, personal communication). About 5% of reattachments fail for unknown reasons. Traction detachment caused by proliferative vitreoretinopathy (PVR: the growth of cellular “membranes” on the retinal surface) remains the most common reason for failure, with a rate of 7–10% in primary surgeries and even higher when a second procedure is necessary. Many studies have shown significant effects of rhegmatogenous RD on functional vision after successful repair. Burton and Tani et al estimated that 30–40% of reattachment patients do not achieve reading ability. A variety of studies estimate that 50% require low-vision aids in order to achieve reading ability (H. Heimann, personal communication). While functional recovery after reattachment is remarkable, it is also true that there is room for improvement.

The development of PVR or subretinal fibrosis (growth of cellular membranes in the subretinal space, i.e., on the photoreceptor surface) is probably the most ominous complication of reattachment. The incidence of PVR is well documented, but that of subretinal fibrosis is not because of the difficulty of resolving these fine cellular membranes by ophthalmic exam. The cellular membranes that form are complex, consisting of at least glial cells, macrophages, and RPE cells. Their attachment to the retina (whether on the vitreal or photoreceptor surface) and contraction can cause wrinkling and redetachment ( Figure 71.1 ). Subretinal fibrosis also effectively blocks the regeneration of outer segments in animal models. PVR was named without a clear link to the actual process of cell division. Indeed, this link is suggested by a variety of data, but not proven. Both cell growth (hypertrophy) and actual proliferation probably play a role (see below). The demonstration that detachment stimulates intraretinal proliferation of all nonneuronal cell types, coupled with the assumption that proliferation is generally a part of scar formation, makes antiproliferative agents attractive prospects for preventing or controlling these conditions. Clinical trials with the common antiproliferative drug, 5-fluorouracil (5-FU), proved disappointing, but other antiproliferative agents are providing more encouraging results in animal models. Evidence in mice lacking the expression of glial fibrillary acidic protein (GFAP) and vimentin demonstrates that inhibitors of these intermediate filament proteins may lead to better treatment of the proliferative diseases because subretinal scars do not form in these animals. There are currently no such agents available for medical use. The only therapy for PVR or subretinal fibrosis is surgical removal of the cellular membranes, but even successful removal may lead to disappointing results and carries its own risk. PVR is covered at greater length in Chapter 78 .

Pathology

For many years the degeneration of photoreceptor outer segments was recognized as the main cellular pathology of RD. The migration of RPE cells from the monolayer and glial cell expansion to form fibrotic lesions or scars on the retina was also recognized in early pathological studies. More detailed studies by electron microscopy and especially the use of immunohistochemical labeling and confocal imaging have revealed many complex cellular responses to detachment extending through all retinal layers ( Figure 71.3 ).

Cell types that have been shown to respond to retinal detachment include the retinal pigmented epithelium, rod and cone photoreceptors, rod bipolar cells, axon-bearing horizontal cells, ganglion cells, Müller cells, and microglia.

Reattachment was assumed to return the retina to its “normal” state based on early observations of outer-segment regeneration (“After surgical reattachment the receptor cell outer segments regenerate, the discs assume a normal pattern, and the phagosomes again return to the retinal pigment epithelial cells” ). Reattachment instead results in what has been referred to as a “patchwork” of recovery across the RPE–photoreceptor interface (Figures 12 and 13 in Fisher et al ).

Etiology

Aging, myopia, local retinal atrophy (i.e., lattice degeneration), and cataract surgery are all well-recognized factors that increase risk of detachment. Less common factors include congenital eye disease, retinoschisis, uveitis, diabetic retinopathy, premature birth, inflammation, or a family history of detachments ( http://www.nei.nih.gov.easyaccess2.lib.cuhk.edu.hk/health/retinaldetach/index.asp#5 ). In some cases there is a clear association with inherited diseases (Norrie disease, Stickler’s syndrome, X-linked retinoschisis) while in other cases a role for inheritance may be suggested but poorly understood. The database, Online Mendelian Inheritance in Man ( http://www-ncbi-nlm-nih-gov.easyaccess2.lib.cuhk.edu.hk/sites/entrez?db=omim ), provides information suggesting many potential roles for inheritance in RD. Predicting risk in an individual is complex because of the number of interacting factors that can come into play. Although there have been major improvements in cataract surgery this procedure still produces a significant increase in risk for rhegmatogenous RD. Vitreous liquefaction and posterior vitreous detachment (PVD), which produces traction on the retina, are key pathogenic mechanisms in rhegmatogenous RD. Before the age of 60, about 10% of patients experience PVD, while this number rises to about 25% between the ages of 60 and 70 and to slightly over 60% in patients over the age of 80. Epidemiological data suggest that the incidence of detachment begins to rise in the fourth decade of life. There is presently no method for preventing vitreous liquifaction and subsequent PVD. Prophylactic vitrectomy or scleral buckle is rarely performed. Laser photocoagulation or cryotherapy is used around retinal breaks or sites of obvious viteroretinal adhesion to increase chorioretinal adhesion and prevent subsequent detachment but the results are not unequivocal. The prevention of detachment in eyes at risk is a worthy research goal.