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About AMD

Age-related macular degeneration (AMD) is the leading cause of blindness in the western world among individuals older than 50 years of age. It is a bilateral condition that has three stages.  Early AMD is characterized by the presence of small or a few medium-sized drusen (yellow spots due to accumulation of material in one layer of the retina) and has a very low risk (<2% chance) of progressing to advanced AMD within 5 years. Intermediate AMD is characterized by the presence of at least one large-sized drusen (greatest linear dimension at least 125 microns,µ) or many (approximately 20 or more) medium-sized drusen (greatest linear dimension at least 63 µ but less than 125µ) or non-foveal geographic atrophy.  Patients with bilateral intermediate AMD have a 25% risk of progressing to advanced AMD within 5 years in one eye, while intermediate AMD with focal hyperpigmentation of the retinal pigment epithelium (RPE) within 1500 microns of the foveal center in one eye with advanced neovascular AMD in the other eye carries a high risk (43% chance) of progressing to advanced AMD within 5 years.1-4 There are two forms of advanced AMD, an atrophic form, termed geographic atrophy (GA) and a neovascular form, termed choroidal neovascularization (CNV). At least two-thirds of the cases that progress from the intermediate to the advanced stage develop the neovascular form of advanced AMD.5-7

Unfortunately, it is impossible to identify which ones among the AMD patients will eventually progress to CNV and when this progression will occur. It is clear, however, that the lesion will grow rapidly once the neovascular process begins. The pathology initially appears at an extra-foveal area and advances to the optic disc area at an average rate of 18 microns per day8-10. Without treatment at this stage, visual acuity may deteriorate dramatically within weeks, when the lesion reaches the sub-foveal areas. One of the factors that delays diagnosis is the fact that the patient is asymptomatic at the early stages of CNV and is utterly unaware of the neovascular process due to effective brain compensation mechanisms.

The three most common symptoms of CNV secondary to AMD reported are: metamorphoses, blurred vision, and scotoma11. These symptoms are the result of anatomical changes in the sub-retinal space and in the sub-RPE space, with subsequent functional deterioration of the photoreceptors in the macular area.

The use of daily oral vitamin supplementation with specific doses of vitamins C and E, beta-carotene, zinc oxide, and cupric oxide can reduce the risk of developing advanced AMD by about 25%. 12

Lucentis (Ranibizumab) has been recently shown to stabilize visual acuity (VA) in patients who developed neovascular AMD, but only 35-40% had improvement in their vision since most of the patients presented with VA already deteriorated to the point of precluding normal daily functions.10, 13

Detection of the condition while good vision functions are still preserved will lead to better treatment outcomes and subsequently reduce the burden of blindness from AMD.

References:

  1. Pizarello LD. The dimensions of the problem of eye disease among the elderly. Ophthalmology 1987;94:1191-1195.
  2. Klein R., Klein BEK, Linton KLP. Prevalence of age-related maculopathy. The Beaver Dam Eye Study. Ophthalmology 1992;99:933-943.
  3. Klein, R., Klein BEK, Linton KLP, DeMets DL. The Beaver Dam Eye Study: Visual acuity. Ophthalmology 1991:98;1310-1315.
  4. Bressler NM, Bressler SB. Preventive ophthalmology. Age-related macular degeneration. Ophthalmology 1995;102:1206-1211.
  5. Bressler NM, Bressler SB, Gragoudas ES. Clinical characteristics of choroidal neovascular membranes. Arch Ophthalmol 1987;105:209-213.
  6. Fine SL. Early detection of extrafoveal neovascular membranes by daily central field evaluation. Ophthalmology 1985;92:603-609.
  7. Bressler NM, Frost LA, Bressler SB, Murphy RP, Fine SL. Natural course of poorly defined choroidal neovascularization associated with macular degeneration. Arch Ophthalmol 1988;106:1537-1542.
  8. Fine AM, Elman MJ, Ebert JE, Prestia PA, Starr JS, Fine SL. Earliest symptoms caused by neovascular membranes in the macula. Arch Ophthalmol  1986;104:513-514.
  9. Age-Related Eye Disease Study Research Group. A Randomized, Placebo-Controlled Clinical Trial of High-Dose Supplementation with Vitamins C and E, Beta Carotene and Zinc for Age-Related Macular Degeneration and Vision Loss: AREDS Report No. 8. Arch Ophthalmol. 2001;119:1417-1436.
  10. Rosenfeld, PJ, Brown, DM, Heier, JS, Boyer, DS, Kaiser, PK, Chung, CY, Kim, RY, the MARINA Study Group. Ranibizumab for Neovascular Age-Related Macular Degeneration. NEJM 2006;355: 1419-1431
  11. MPS. Five-year follow-up of fellow eyes of patients with age-related macular degeneration and unilateral extrafoveal choroidal neovascularization. Macular Photocoagulation Study Group. Arch Ophthalmol 111, 1189-99 (1993).
  12. Vander, J. F., Morgan, C . M. & Schatz, H. Growth rate of subretinal neovascularization in age-related macular degeneration. Ophthalmology 96, 1422-6; discussion 1426-9 (1989).
  13. Brown, DM, Kaiser, PK, Michels, M, Soubrane, G, Heier, JS, Kim, RY, Sy, JP, Schneider, S, the ANCHOR Study Group. Ranibizumab versus Verteporfin for Neovascular Age-Related Macular Degeneration. NEJM 2006; 355: 1432-1444