RI: An Early Warning Sign for AMD
Mark F. Pyfer, MD
Your RI, or Rod Intercept (as measured by the AdaptDx) can provide the earliest warning sign of age-related macular degeneration (AMD) before it affects your vision.
What if a single number could help you protect your sight?
What if a simple test could provide an early warning of a sight threatening disease?
The disease is called age-related macular degeneration, or AMD, and it affects over 9 million mostly older Americans.
AMD is the leading cause of irreversible blindness
Unfortunately nearly 80% of those affected suffer substantial irreversible vision loss before treatment begins.
Mark F. Pyfer, MD (Northern Ophthalmic Associates, Wills Eye Hospital): “AMD is the leading cause of irreversible blindness among adults over the age of 60 in the Western world. It is a progressive chronic disease in which the central part of your vision, the part we use for reading, seeing people’s faces, or driving, slowly deteriorates.”
Like glaucoma, which affects about 3 million Americans, macular degeneration may not produce symptoms until damage has already been done. Since these symptoms can come on so slowly, they are often confused with a normal aging process.
Dark Adaptation Test Helps Diagnose AMD
Gregory R. Jackson, PhD (Chief Technology Officer, MacuLogix): “Until now there wasn’t a simple, effective way to determine if people had macular degeneration before they already had symptoms of vision loss. We applied insights about the relationship between what’s called dark adaptation and the health of the retina to develop a new test.”
Think of going from bright sunlight into a darkened movie theater. How long does it take your eyes to adjust? That is dark adaptation.
Gregory R. Jackson: ”Research has shown that the cells responsible for night vision are affected by macular degeneration long before and more severely than those cells responsible for day vision. Thus we created a device to measure the dark adaptation function.”
Rod Intercept: An Early Warning Sign of AMD
That device is called the AdaptDx. During the dark adaptation test, the patient sees a flash of light, and then pushes a button each time they see one in a series of fainter green lights. The result is a single number: the rod intercept or RI that reflects the amount of time it takes the rod cells in the patient’s retina to adjust to darkness. Clinical studies have shown that an RI of 6.5 minutes or less is consistent with good eye health. But anything over 6.5 is an early sign of macular degeneration. So knowing your RI can help protect your sight and provide an early warning of age-related macular degeneration.