Dry Age-Related Macular Degeneration: Optometry Case #26

This is dry (non-neovascular) age-related macular degeneration, and the left eye has already reached its advanced stage. The disease has exactly two clinical forms, and most of this case is an argument about which one is in front of you. The dry form builds slowly: drusen collect under the retina — hard drusen have definite boundaries, soft drusen have indistinct ones, and soft drusen can become confluent into larger drusen and go on to lift the pigment epithelium into drusenoid detachments — while the retinal pigment epithelium turns patchily hyperpigmented and hypopigmented. Vision loss is gradual in the early and intermediate stages, which is exactly what two years of slow central blurring, slow reading, and abandoned night driving look like. The advanced dry stage is geographic atrophy: a sharply delineated round or oval area of hypopigmentation, depigmentation, or absence of the retinal pigment epithelium, at least 175 micrometres across, enlarging over time and tending to be bilateral. Once it involves the centre of the macula it causes significant visual loss, which is why the position of the patch matters as much as its presence. Imaging tells the same story three ways: tomography shows drusen as nodular elevations of the pigment epithelium (area and volume are measurable and serve as a prognostic marker) and an atrophic patch with absent external limiting membrane, absent photoreceptor inner and outer segment junctions, and an absent pigment epithelium and Bruch membrane complex; autofluorescence shows the atrophy as hypofluorescent, because the pigment epithelium producing the signal is gone, with a slightly hyperfluorescent border whose fluorescence is a marker for progression — and it is more sensitive than clinical examination at picking progression up. What is missing carries as much weight as what is present. The neovascular form is defined by a choroidal neovascular membrane with fluid or blood in the intraretinal or subretinal plane, and it causes blurring and distortion, especially for near vision. Here there is no fluid, no blood, and the Amsler lines are unbent — a patch of grid gone missing, not a patch of grid warped. Management follows from staging: intermediate disease, or advanced disease in at least one eye, should be started on the AREDS supplement. The original AREDS formulation was 500 mg vitamin C, 400 IU vitamin E, 15 mg beta carotene, and 80 mg zinc oxide with 2 mg cupric oxide; AREDS 2 is 500 mg vitamin C, 400 IU vitamin E, 80 mg zinc oxide, 2 mg cupric oxide, 10 mg lutein, 2 mg zeaxanthin, and 1 g omega-3 fatty acids, with beta carotene removed because of lung cancer risk in smokers — which is not a footnote for a patient who still smokes. Increasing age, smoking as an independent risk factor, and complement-related genetic variants all raise risk, and prevalence is higher in non-Hispanic whites than in Black and Hispanic populations.