Clinicians are beginning to recognize that dark adaptation testing may indicate a diagnosis of age-related macular degeneration in patients who have no other clinical signs.
The diagnostic testing device, AdaptDx (MacuLogix), has been shown in a clinical trial to identify patients at risk for vision loss who have no other detectable signs of AMD by using abnormal dark adaptation (DA) as a biomarker for disease.
The role of DA in AMD could be significant, “as research has found that the disease is three times more prevalent than glaucoma, with one out of eight adults over 60 years and one out of three over 75 years afflicted,” according to Greg Jackson, PhD, chief scientific officer, MacuLogix and creator of AdaptDx, in an interview with Primary Care Optometry News.
The Eye Diseases Prevalence research group published these statistics in 2004.
Glenn S. Corbin, OD, a private practitioner in Wyomissing, Pa., and Section of Optometry chief at Penn State Health St. Joseph Medical Center, received the first AdaptDx unit off the assembly line in the U.S. more than 2 years ago.
“The idea of performing dark adaptation in practice was new to eye care,” Corbin told PCON. “I looked at the technology; the platform was similar to an autoperimeter, and I was intrigued by it.
“We are able to find people that would have normally been undiagnosed until a later stage of the disease,” he continued. “I would have never thought that a couple of drusen could indicate an early diagnosis of AMD. Now the technology tells me their dark adaptation is abnormal and they do have early signs of AMD.”
Based on this testing, Corbin can provide those with disease risk factors or a family history a much more accurate response, he said. Additionally, he can diagnose the disease at an earlier stage.
“We’ve learned of an entity called subclinical AMD, where a patient appears to have a healthy retina, and you cannot physically see drusen, but they may have a sheet of drusen underneath that is not clinically visible upon examination,” Corbin added.
He believes that every optometrist should test for DA in their practice.
“With the aging population, longer lifespans and increased visual demands that are much different than a generation or two ago, it’s critical to identify patients before they start losing vision,” Damon Dierker, OD, FAAO, of the Eye Surgeons of Indiana and adjunct faculty member at the Indiana University School of Optometry, said in an interview
Corbin added: “I screen patients as a precaution or if there’s a family history of AMD. Clinically, we may not observe AMD signs, but based on abnormal DA testing results, we can feel confident that they have the disease.”
AdaptDx is changing the timeline for AMD diagnosis, according to Leo P. Semes, OD, FAAO, former professor of optometry at the University of Alabama at Birmingham and a Primary Care Optometry News Editorial Board member.
Jackson spearheaded DA research during his graduate days in the mid-90s in the ophthalmology department of the University of Alabama at Birmingham. He was interested in why older adults had trouble with night vision, when their day vision was adequate.
“We found that older adults, many in fact, had normal retinal health through imaging by color stereo fundus photographs, but they had clinically abnormal dark adaptation, which meant terrible night vision. We couldn’t figure out why,” Jackson said.