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.
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.
Figure 2: Wet AMD (Photo courtesy of Daniel Epshtein, OD, FAAO)
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.
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
Figure 3: Dark Adaptation Curve
A Summary of the ALSTAR Study
In 2014, the ALSTAR
study assessed dark adaptation in 325 adults ages 60 and up who had all been deemed to have good macular health via clinical exam. After 3 years, subjects who showed impaired dark adaptation were twice as likely to develop AMD compared to individuals of normal adaptation.
The results of the ALSTAR study showed that dark adaptation is clinically useful in identifying patients at the earliest stages of AMD, before the appearance of detectable clinical evidence.
Adapt Dx Diagnostic Tools for AMD
The results of the ALSAR study have inspired the development of new diagnostic tools that use dark adaptation changes to help detect early AMD. The AdaptDx
is a simple AMD screening test that has been developed following the ALSTAR study. AdaptDx tests dark adaptation via a rapid, auto-guided screening to allow healthcare providers to quickly assess all patients over a certain age for early AMD.
AdaptDx can be worn over the head, which is more comfortable for patients, and is guided by Thia, the AI technician. The test is interpreted by the OD and, if the Rod Intercept is at or above 6.5 minutes, more extensive testing can be performed.
Since AdaptDx measures dark adaptation, it is not affected by cataracts
, amblyopia, or color deficiency, which are factors that may affect other methods of AMD testing such as fundus evaluation and OCT.
Other Recent Diagnostic Tools
Foresee Home Monitor
: The Foresee Home Monitor®
is the first FDA approved device for home monitoring
of AMD. The device is intended for patients who are at high risk of converting from dry AMD to wet AMD and offers a 6-minute test (3 minutes per eye) to help patients self-monitor between doctor’s appointments. The device is covered by Medicare for qualified patients and endorsed by the Macular Degeneration Association
Implementing New Findings in Practice
The AdaptDx can be integrated into most practice settings. Maculogix, the creator of AdaptDx, recommends having patients screened based on age. The AdaptDx screening test can be performed by a technician during pretesting. Since Thia guides the patient throughout most of the test, this is a great time for office technician to catch up on other tasks. Another attractive feature of the AdaptDx is the fact that it is reimbursable
by vision care plans under CPT code 92284 with an average reimbursement of $60.63.
Meanwhile, patients who have been diagnosed with AMD can benefit from the Foresee Home Monitoring system to help track vision changes.
Tackling Subclinical AMD
Early diagnosis of AMD can help prompt conversations about positive lifestyle changes to help reduce progression including:
- Smoking cessation: Patients should be encouraged to stop smoking as it is strongly linked to advanced AMD progression. Primary care physicians often have resources for patients who struggle with quitting.
- A healthy diet: A diet that is high in antioxidants is thought to be protective against AMD. The Mediterranean Diet has been linked to lower incidences of AMD as well. Starting the AREDS2 supplement may also be helpful in subclinical/early cases of dry AMD.
- Exercise: Regular exercise helps boost antioxidant enzymes, which can also help slow the progression of AMD.
- Early introduction to low vision: While visual acuity is often good during the early stages of AMD, educating the patient about the potential of vision loss and the available low vision resources can help prepare the patient for future outcomes.
While AMD continues to be a sight-devastating disease, recent scientific advances have allowed early detection and more careful monitoring, which can lead to earlier and more successful interventions. The AdaptDx uses the process of dark adaptation to help detect early AMD before the appearance of pigmentary mottling or drusen. The Foresee Home Monitor can be used by patients at home to help more accurately monitor the progression of AMD in between office visits.
While research is still underway to improve treatment for both wet and dry AMD, early detection and intervention as well as careful monitoring can help slow AMD progression, allowing patients to retain their sight.