Association Between Peripheral Changes, AMD and Impairments in Dark Adaptation Identified

iInês Laíns, MD

A new study has revealed an association between dark adaptation (DA) and peripheral changes in patients with age-related macular degeneration (AMD).

Led by Harvard University research fellow Inês Laíns, MD, the discovery of the link between DA and peripheral reticular pigmentary changes, including a peripheral mottled decreased fundus autofluorescence (FAF) pattern, could aid new insights into the clinical significance of peripheral changes in AMD and provide a useful metric for AMD detection in early stages, speeding diagnosis and thereby treatment for patients, according to the authors.

Conducted by the Harvard Ophthalmology AMD Center of Excellence in Boston, Massachusetts, the prospective, cross-sectional study included 128 eyes (n = 72) from patients over the age of 50 (mean, 68.2 ± 6.9).

In total, 75% of study patients (n = 96) were diagnosed with AMD and 25% (n = 32) had no AMD or other vitreoretinal disease or diagnosis, serving as control eyes. All patients received a full-ophthalmological examination including comprehensive eye examination, best-corrected visual acuity (BCVA) examination, and current refraction, slit-lamp biomicroscopy, dilated fundus examination, and intraocular pressure testing. Study participants also completed a questionnaire on medical history, demographics, and medications.

All patients received additional ultra-widefield (UWF) pseudocolor and FAF photographs, as well as 7-field color fundus photographs analyzed by independent graders who noted any peripheral changes to the perimacular, midperipheral, and far-peripheral zones. Laíns wrote that to determine DA, each patient was tested—in both eyes—with a DA-extended protocol lasting 20 minutes to determine any prolonged adaptation to dark-adapt.

Data from the study was analyzed by a multilevel mixed-effect model to determine any correlated outcomes and revealed that delayed rod-intercept times (RIT) were associated with the presence of reticular pigmentary changes in the midperipheral (ß = 4.3; P = .012) and far-peripheral zones (ß = 8.4; P <.001), which included granular increased patterns, nummular decreased patterns, and a mottled decreased FAF pattern in the midperipheral zone (ß = 4.4; P = .031).

The mottled decreased FAF pattern, Laíns wrote, “reflects areas of generally decreased autofluorescence in an uneven irregular pattern.”

Laíns and colleagues suggested that there is a significant association between RIT and reticular pigmentary changes in the mid- and far-peripheral zones and mottled decreased patterns in the midperipheral zone, “even after accounting for relevant confounding factors such as age, AMD stage, and specific AMD changes.” Laíns argued that, in the past, these changes have been considered an “acquired, age-related process” but that the study’s findings suggest that reticular pigmentary changes are “more common in eyes with macular signs of AMD than in age-matched normal eyes.”

Some of the pigmentary changes recorded, according to Laíns and colleagues, “correspond to a decreased pigmentation of the [retinal pigment epithelium]” or peripheral reticular degeneration, which “has been associated with complement factor H risk polymorphisms.” Laíns noted that both decreased pigmentation of the retinal pigment epithelium and peripheral reticular degeneration are traditionally associated with AMD.

Laíns and colleagues wrote that analysis of new imaging options like UWF and FAF, which can reveal information that invisible or is poorly visible through solely other methods alone, can help clarify the pathogenesis of peripheral patterns and provide insights into their relevance in clinical terms.

Their study, Laíns says, “presents the first assessment of peripheral changes in AMD and time to dark-adapt” and could establish DA as a “promising functional outcome measure” in AMD. Although they suggested that more research is needed and that although their study notes a significant link between peripheral reticular pigmentary changes and DA, the possible mechanisms behind these peripheral changes and their links to DA and AMD remain to be completely established.

The study, "Peripheral Changes Associated With Delayed Dark Adaptation in Age-related Macular Degeneration" was published in the American Journal of Ophthalmology. It was developed by the faculty at Massachusetts Eye and Ear, part of the Department of Ophthalmology at Harvard Medical School.