Retinal Disorders

Macular Degeneration

Age related macular degeneration (AMD) is the leading cause of severe vision loss in developed nations.  Vision loss usually results from one of two forms of AMD-central geographic atrophy( dry degeneration) or choroidal neovascularization (wet degeneration).  Advanced AMD occurs more frequently in European derived populations, is less frequent in Asians, and is rare in Africans.  In the United States an estimated ten percent of adults over 75 years of age have AMD with some visual loss.  Risk factors for developing AMD include age, race, blue iris color, and cigarette smoking.  Hypertension is associated with increased risk of neovascular AMD.

Most patient's are asymptomatic in the early stages of AMD.  Patient's with geographic atrophy present with gradual vision loss and may note difficulty reading.  Patients with neovascular AMD often present with sudden severe visual loss or metamorphopsia ( blurring and distortion of straight lines).  Diagnosis of AMD can be made when the retina is visualized during a complete ophthalmic examination.  Several ancillary can be helpful in defining the nature of AMD.  Fundus photographs serve to record the presence and extent of geographic atrophy, sub-retinal hemorrhage, and pigment epithelial detachment.  Fluorescein angiography and Indocyanine green angiography provide images of choroidal neovascularization that define its location and suitability for treatment.  Optical coherence tomography determines the amount of subretinal and intraretinal fluid leakage from choroidal neovascularization.

No treatment is currently available for the non-neovascular form of AMD.  Several interventions, however, may be of benefit to patients with early non-neovascular AMD.  Smoking cessation and control of hypertension  are supported by population based studies as ways of modifying risk for advanced AMD.  Nutritional supplements, have been shown to reduce the risk of progression to advanced AMD  in patients with non-central geographic atrophy, large drusen, or advanced AMD in one eye.  The Age Related Eye Disease Study. a National Eye Institute sponsored study  identified supplementation with vitamins C, and E, beta carotene, zinc, and copper as beneficial in this regard.  This formula is available in a number of commercial products including the Preservision line  by Bausch and Lomb.  Other supplements including lutein, zeaxanthin, and omega-3 fatty acids have shown promise but have not been studied as rigorously.

The treatment of neovascular AMD has been revolutionized  by the introduction of antiangiogenic agents.  The two agents most widely used in this class today are ranibizumab (Lucentis, Genentech) and bevacizumab (Avastin, Genetech).  Both are delivered by direct injection into the vitreous cavity of the eye and block the action of vascular endothelial growth factor (VEGF).  The frequency of treatment is adjusted to patient response, but repeated injections every four to eight weeks is the norm.  These frequent intravitreal injections are associated with a small risk of serious intraocular  complication, especially endophthalmitis( intraocular infection).  Despite this risk, however, these drugs represent a major advance over previous treatments for AMD that included laser photocoagulation and photodynamic therapy.