Dark Adaptation and Other New Breakthroughs in AMD Diagnosis

Nov 16, 2021
6 min read
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Age-related macular degeneration (AMD or ARMD) is the leading cause of irreversible blindness in adults over age 50. Research into diagnosis and treatment for AMD has continued to help clinicians diagnose and treat at all stages of the disease. Here is what you need to know about recent AMD breakthroughs.

Overview of Macular Degeneration

Age-related macular degeneration is characterized by the thickening of Bruch’s membrane and the accumulation of drusen in the macula. Due to its effects on the macula, AMD can be devastating to visual acuity and dramatically decrease quality of life for patients.

Early changes such as the appearance of hard drusen or pigmentary mottling may or may not cause vision loss and can be seen via fundus observation or optical coherence tomography (OCT).

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Figure 1: Drusen deposits in dry AMD (Photo courtesy of Daniel Epshtein, OD, FAAO)

Drusen accumulates over time resulting in progression to either the dry or wet form of AMD. Dry AMD, which is the more common form of AMD, is characterized by the presence of hard or soft confluent drusen with geographic atrophy in the later stages. Meanwhile, wet AMD is characterized by choroidal neovascularization.

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Figure 2: Wet AMD (Photo courtesy of Daniel Epshtein, OD, FAAO)

AMD Treatment: In the early stages, AMD progression can be slowed with AREDS2 supplementation, which has been shown to successfully slow the progression of AMD from intermediate to advanced by 25%. Wet AMD requires anti-VEGF injections and laser treatment to preserve vision.

AMD Diagnosis: Several clinical tools exist to detect and monitor AMD. These include the Amsler grid, fundus fluorescein angiography, OCT, fundus autofluorescence, and fundus observation (via photography and biomicroscopy).

Dark adaptation leads to new diagnostic tools for AMD

In the past, pigmentary mottling and drusen formation were the first signs of AMD. The Alabama Study on Early Age-Related Macular Degeneration has recently shown that we may be able to identify affected individuals even earlier by testing for impaired dark adaptation.

Dark adaptation, a review

Humans can see in a variety of lighting conditions because we have both rods and cones present in the retina. Dark adaptation measures the amount of time it takes to recover scotopic or night vision after exposure to bright lights. Research shows that most healthy individuals will start to see better in the dark after around five to ten minutes. This is when modulation of vision is switched from cones, which are most sensitive in brighter illumination, to rods, which are most sensitive to dark illumination; this is also known as the Rod-Cone Break.

Dark Adaptation Curve