December 10, 2015

Delayed Dark Adaptation Predicts Onset of Dry AMD


Delayed Dark Adaptation Predicts Onset of Dry AMD

A recent study* at the University of Alabama has found that measurement of the time it takes older adults’ eyes to adapt to the dark can predict onset of dry age-related macular degeneration (dAMD).
Using a computerized dark adaptometer, 325 persons with healthy eyes were each subjected to a flash of light in one eye, and their dark adaptation (DA) time was measured. At baseline, 263 of them had normal DA, meaning that their eyes recovered in under 12.3 minutes. 62 of them had “abnormal DA” with times exceeding 12.3 minutes. Three years later, those with abnormal DA were about 2 times more likely to have developed dAMD in the tested eye.
These results offer another biomarker for identifying future onset of AMD. Nutrient biomarkers have been identified, but those are not always accurate. Genetic inflammatory markers are more consistent, but only two gene pairing mutations (SNPs) have been studied in any depth. DA measurement is a relatively simple and seemingly accurate method that may prove to be a valuable diagnostic tool. According to the study authors, “The biological relevance of this test is high, because it assesses translocation of vitamin A derivatives across the retinal pigment epithelium and Bruch’s membrane, 2 tissues with prominent age- and AMD-related pathology”.
*Source: Delayed Rod-Mediated Dark Adaptation Is a Functional Biomarker for Incident Early Age-Related Macular Degeneration Cynthia Owsley, et al (Ophthalmology online, October 29, 2015, Manuscript no. 2015-1327)
Read the study abstract

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