AdaptDx: The Path to Invention
Gregory R. Jackson, PhD
Greg Jackson, PhD, is the inventor of the AdaptDx® dark adaptometer and Chief Scientific Officer of MacuLogix®. He explains why he developed this technology for detecting and monitoring early age-related macular degeneration (AMD). He also discusses how the AdaptDx works and its high degree of accuracy.
Why did you develop the AdaptDx dark adaptometer?
The Beginnings of the AdaptDx
This research began in 1996 at the University Alabama at Birmingham where I was a student and I was doing my doctoral dissertation on aging, normal aging and dark adaptation. The reason why we developed the AdaptDx is we made a connection between severe impairment of dark adaptation and the presence of age-related macular degeneration.
In fact, in the beginning, we were interested in normal older adults that had dramatically impaired dark adaptation. We sent these patients to retina specialist, we sent their photographs to reading centers, and they came back telling us these patients had normal retinal health but clinically abnormal dark adaptation. And we followed these patients and low and behold two, three, four years later they developed a clinical diagnosis of age-related macular degeneration. That’s what began our exploration into this area.
Passion for Early Diagnosis of AMD
The reason why we developed the AdaptDx is we’re passionate about early diagnosis of patients with AMD, so that it can have earlier treatment, and better patient outcomes.
How does the AdaptDx work?
The AdaptDx Test: What the Patient Experiences
The test is a test of dark adaptation or how fast someone adjusts from day vision to night vision.
At the beginning of the test, which is done in the dark, we show the patient a camera flash. That flash is about the intensity of your cell phone camera flash and its focal located outside the fovea so it’s non-irritating. And that’s to get everyone’s retinal illumination to a standardized level. After that we present a stimulus to the patient and whenever the patient sees this light, the small flash of light, they press a button. If they press it, it becomes dimmer. If they don’t press it, it becomes brighter. What we’re trying to measure is the least amount of light they can see at a given point at a time. After we measure what is called a threshold, the patient has a rest break. Over time, they can see progressively dimmer flashes of light and we can track out what’s called the dark adaptation function.
Fully Automated Dark Adaptometer
The AdaptDx is the first adaptometer that does not require pupil dialation for accurate results. Our camera is constantly monitoring the pupil of the patient and taking an area calculation of the patient’s pupil size, and then using that to correct the calibration to a standard light level.
Rod Intercept: The 6.5 minute Cut Point
We validated our 6.5 minute cut point for the Rod Intercept in a multi-site clinical validation study. The way you do such studies is you measure the patients’ dark adaptation in a large number of AMD patients and in patients with normal retinal health; use the 6.5 minute cut point to determine who has AMD and who is normal. Independent of that, you take fundus photographs of the patient’s eyes and have a masked reader, who is a trained retina specialist, determine whether or not they have age-related macular degeneration or normal retinal health, using the AREDS classification system. Then you compare the dark adaptation results to the gold standard.
AdaptDx is 90% Accurate
What we found is that using the 6.5 minute cut point, you can correctly identify 90% of the AMD patients, that in fact have AMD, and correctly identify 90% of normals, that have normal retinal health, according to AREDS, for an overall accuracy of over 90%. And 90% is a very high accuracy.