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How Physics Can Help Patients with Macular Degeneration

The views expressed are those of the author and are not necessarily those of Scientific American.

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Amsler grid as it might appear to someone with age-related macular degeneration. A new idea uses software or an optic slab to correct a patient’s specific visual distortion. Credit: National Eye Institute, National Institutes of Health. Source page 14

Walter Kohn, who shared the Nobel Prize in Chemistry in 1998 “for his development of the density-functional theory” (the other recipient that year was John A. Pople “for his development of computational methods in quantum chemistry”), would be the first to tell you that he isn’t an expert in optics. I know, because that’s what he told me when we chattd after his talk at the Lindau Nobel Laureate Meeting today.

But when his wife developed age-related macular degeneration a few years ago, “I asked myself as a theoretical physicist, is there something I can contribute to this issue?” His clever solution someday could be applied to a dynamic “translator” for the particular distortion a patient experiences either in handheld computers or an optical corrective lens.

(You can read all our coverage of the Lindau meeting this week, including the “30 under 30” profiles series of young scientists attending, in this In-Depth Report. Also see the Lindau Nobel Community blogs.)

Age-related macular degeneration, or AMD, is the most common cause of legal blindness. Patients can still see, but suffer blurred vision from damage to the macula in the center of the retina (For more info, see this National Eye Institute page on Facts about Age-Related Macular Degeneration.) While research proceeds on treatments from stem cells to retinal implants, Kohn wanted to help patients more immediately. His novel idea? Use the Amsler Grid, a graph-paper-like pattern used for diagnosing AMD, to develop a correction.

When people with healthy eyes look at the Amsler Grid, they see its straight horizontal and vertical lines, with a red dot at center. AMD patients, however, perceive a distortion about two or three centimeters in diameter reminiscent of graphics that show a bend in spacetime (the peripheral lines are not distorted).

Software lets an AMD patient, using a mouse, pull the virtual lines until he or she perceives the grid as “perfect,” yielding a spatial diagnosis of the specific distortion a person experiences. Kohn uses these results to create a correction for that patient. In one experimental device, a handheld computer scans the printed page, using software to perform dynamic compensation, distorting the text to make it readable for patients. “I think you will agree that we can feel fairly satisfied that we’ve made progress,” he said, showing an image of the corrected text.

Kohn is also exploring the use of a slab of optical material to perform the visual correction, and has made a prototype at the University of California at Santa Barbara machine shop. The patient could hold the optical slab of refractive material over text, just like the magnifying glass people use for seeing small type—only the surface of Kohn’s slab resembles ocean currents.

Kohn says he successfully has tested both techniques on a patient he calls, “Eve,” a 60-year-old accountant. He is now working with the Institut de la Vision in France and others on possible commercialization of both ideas. “Things are very exciting,” he added.

Mariette DiChristina About the Author: Editor in Chief, Mariette DiChristina, oversees Scientific American,, Scientific American MIND and all newsstand special editions. Follow on Twitter @mdichristina.

The views expressed are those of the author and are not necessarily those of Scientific American.

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  1. 1. jimdoc 2:34 pm 07/7/2012

    You wrote:
    “Age-related macular degeneration, or AMD, is the most common cause of legal blindness.”

    This is somewhat misleading.
    According to WHO estimates, the most common causes of blindness around the world in 2002 were:
    1. cataracts (47.9%),
    2. glaucoma (12.3%),
    3. age-related macular degeneration (8.7%)

    Link to this
  2. 2. bucketofsquid 11:06 am 07/11/2012

    Until we can prevent or reverse macular degeneration, corrective lenses make sense to me. The only questions are; how often does the distortion change and what price tag are we facing?

    Link to this
  3. 3. voyager 2:53 am 07/14/2012

    I’ve got a personal stake in this, having been diagnosed with degeneration. I was told that the term is specific in the sense that there’s a physical corrupting of cells at the center of the retina, and among those the deterioration of cells related to seeing in relative darkness is disproportionately high. It’s borne out in my case: a blind spot in the center, not just wavy lines, and terrible night vision now. And my lines are only slightly wavy–early stages. How could such a condition possibly be relieved with corrective lenses?

    Link to this
  4. 4. mselmke 11:55 am 08/1/2012

    You can download a similar software on my webpage to try out the approach to straighten images:

    Link to this

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