Age Related macular degeneratIon-ClassIfIcatIon Bilge Çınar

IntroductIon The leading cause of blindness for those over age 50. Its prevalence increases with age. Drusen, which are tiny yellow or white accumulations of extracellular material that build up between Bruch’s Membrane and the retinal pigment epithelium of the eye, are increasingly common with age. Other risk factors include gender (female > male), ethnic origin (white>> black), diet, cardiovascular risk, smoking, pigmentary changes in the macula, family history of macular degeneration, and hypermetropia.

ANATOMY Macula Foveola Fovea 5 mm in diameter Central point of fovea 4 mm temporal, 0.8mm inferior to optic disc 0.35mm in diameter Thinnest part of the retina Cones only Fovea High levels of visual acuity Depression at the center of the macula

classIfIcatIon Non-neovascular (dry) AMD Neovascular (wet) AMD

Non-neovascular (dry) Amd Accounting for 90% of AMD Gradual but potentially significant reduction in central vision. Characterized by drusen (hard or soft) and RPE changes (focal hyperpigmentation or atrophy).

Non-neovascular (DRY) amd- hIstology Gradual loss of the RPE/photoreceptor layers Thinning of the outer plexiform layer Thickening of Bruch’s membrane Atrophy of choriocapillaris, exposing the larger choroidal vessels on examination.

Non-neovascular (DRY) amd- hIstology Drusen are; PAS-positive amorphous deposits lying between the RPE membrane and the inner collagenous layer of Bruch’s membrane. They may become calcified.

Figure 1: Severe dry AMD with extensive area of large confluent drusen, pigmentary changes, and early RPE atrophy.

Neovascular (wet) Amd Much less common Rapid and severe loss of vision Accounts for up to 90% of legal blindness due to AMD.

Neovascular (wet) Amd- hIstology New fragile capillaries grow from the choriocapillaris through the damaged Bruch’s membrane. Those new capillaries proliferate in the sub-RPE (type I membranes) and/or subretinal space (type 2 membranes). Associated hemorrhage, exudation, retina or RPE detachment, or scar formation. Type I membranes are more common in AMD with diffuse RPE and Bruch’s membrane disease Type 2 are more common in younger patients with focal disease of the RPE and Bruch’s membrane (e.g., with POHS).

Figure 2: Neovascular AMD with a large choroidal neovascular complex and extensive subretinal and sub-RPE hemorrhage.

Kaynak: Oxford American handbook of ophthalmology / edited by James C. Tsai … [et al.]. p. ; cm. Other title: Handbook of ophthalmology Includes index. ISBN 978-0-19-539344-6 1. Ophthalmology—Handbooks, manuals, etc. I. Tsai, James C. II. Title: Handbook of ophthalmology. [DNLM: 1. Eye Diseases—Handbooks. WW 39] RE48.9.O94 2011 617.7—dc22 2010028006