Sunday, November 13, 2011

Retinal Pigment Epithelium (RPE) Detachment

Signs and Symptoms
In most instances, serous detachment of the RPE occurs asymptomatically. Only in those cases in which the macula is affected will patients report blurred vision, metamorphopsia, micropsia, or positive scotomas. Other associated clinical findings may include induced hyperopia and delayed retinal recovery time on the photostress test. Most individuals with RPE detachment are male, between the ages of 20 and 60 years. The history often reveals predisposing or concurrent ocular conditions such as macular degeneration, idiopathic central serous chorioretinopathy (ICSC), angioid streaks, presumed ocular histoplasmosis syndrome (POHS), or hereditary choroidal degeneration. In other cases, the condition occurs idiopathically.

RPE detachment appears ophthalmoscopically as single or multiple, well-circumscribed round or oval lesions within the posterior fundus. The lesions are typically dome-shaped with slight elevation and appear yellow to orange in color. A reddish "halo" is often seen around the base of the detachment, and overlying pigment defects such as clumping or mottling are commonplace. Lesions may vary in size from one-fifth to over 5 disc diameters (DD), but most are less than 1 DD. Fluorescein and indocyanine green (ICG) angiography show early hyperfluorescence of the entire RPE detachment, which persists throughout the angiogram demonstrating late pooling. Leakage into the sensory retina occurs only in cases of concurrent serous retinal detachment.

RPE detachment is a non-specific anatomical alteration that may result from any number of choroidal disorders that disrupt the normal junction between the basement membrane of the RPE and the inner collagenous layer of Bruch’s membrane. This disruption permits serous fluid from the underlying choriocapillaris to gain access into the sub-RPE space. Age-related macular degeneration, choroidal neovascular membranes, high myopia, angioid streaks, hereditary choroidal degeneration, POHS, and tumors of the choroid have all been identified as precipitating conditions in the development of RPE detachment. Idiopathic cases are sometimes associated with ICSC; some believe these two conditions to represent a continuum of a similar underlying pathology. Uncomplicated idiopathic serous detachments of the RPE often resolve spontaneously, however, those associated with more generalized damage to the choriocapillaris may be complicated by hemorrhage, choroidal neovascular membrane formation, and disciform scarring.

Most patients under the age of 55 who present with small serous RPE detachments without evidence of other retinal or choroidal disease enjoy an excellent prognosis without intervention. This is particularly true if the lesion is outside of the fovea and there is no associated subretinal fluid.

Older patients who manifest RPE detachment without angiographic evidence of a choroidal neovascular membrane have a 25-30 percent chance of developing such membranes during their lifetime, and therefore warrant careful observation as well as weekly home monitoring with an Amsler grid.

Those patients over the age of 55 who present with associated choroidal neovascular membranes and/or hemorrhagic RPE detachments have an exceedingly poor visual prognosis. Focal laser photocoagulation is indicated for these patients.

Clinical Pearls

Approximately 90 percent of cases of RPE detachment have or will manifest concurrent serous retinal detachment over the natural history of the disorder. In cases of idiopathic RPE detachment, a striking similarity with ICSC is seen in the predisposed patient population; i.e. male, average age of 44 years, and a moderate to severe emotional stress level.

The presentation of RPE detachment is quite characteristic. Nonetheless, one must be sure to rule out other conditions that may appear similar from an ophthalmoscopic perspective. These include: ICSC, malignant melanoma, metastatic carcinoma, choroidal hemangioma, and Best’s disease (vitelliform dystrophy). History and angiography are the most helpful factors in making this differential diagnosis.

RPE detachment in patients over 55 years of age should be considered secondary to choroidal neovascular membrane, rather than idiopathic, until proven otherwise. Prompt fluorescein angiography is mandatory in these cases.

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