July 2009

 

OPHTHALMOLOGY NEWS

 

Early cataract detection tool developed


by Rich Daly EyeWorld Contributing Editor

 

 

Clinical applications may include tracking the efficacy of cataract prevention treatments or screening for early cataracts in middle-aged post-LASIK patients

A close-up view of a brunescent nuclear cataract

The DLS probe (on right) against compared to other probes

Dr Datiles testing a patient with the DLS device

The dynamic light scattering principle compared to radio

An experiment aimed at showing the effectiveness of Tempol H in preventing cataract formation Source: Manuel B. Datiles III, M.D.

New technology developed by federal researchers may allow the earliest detection yet of cataracts that are not yet clinically visible.

The device, developed and studied by researchers from National Eye Institute (NEI) and NASA, uses a compact fiber-optic probe developed for the space program that allows the first non-invasive early detection of cataracts. The dynamic light scattering technique employed by the system measures the amount of alpha-crystallin protein loss in even clinically clear lenses.

One among the several proteins involved in cataract formation, alpha-crystallin serves as an anti-cataract molecule by binding to other proteins when they become damaged. This process prevents damaged proteins from aggregating to form a cataract. The technology detects the amount of alpha-crystallin—which is fixed at birth—to determine the amount of the protein that has been eliminated by factors such as radiation exposure, smoking, diabetes, or other causes.

The cross-sectional study of 380 eyes in 235 patients age 7 to 86 who had clinical nuclear lens opacity grades of 0 to 3.8, based on the Age-Related Eye Disease Study, used the device to assess alpha-crystallin content. The authors devised an alpha-crystallin index (ACI) to measure the amount of the unbound protein that was in each lens and found an association between the alpha-crystallin index and increasing nuclear opacity and aging. Even among older study participants, age 60 to 70, the study found a significant decrease in the ACI is associated with increasing nuclear lens opacity grade. The decrease in the ACI remained significant even after adjusting for age within this group.

“This is important because it has helped to identify how cataracts develop,” said Manuel B. Datiles III, M.D., NEI medical officer, Bethesda, Md., and lead author of the study published in the December 2008 issue of the Archives of Ophthalmology. “Clinicians could use the device to monitor patients even before they develop symptoms of a cataract and tell them that they need to change dangerous behaviors.”

Although no commercial version of the device is yet available, future clinical applications may include using it to warn patients that they need to reduce their cataract risk through lifestyle changes, such as decreasing sun exposure, quitting smoking, stopping certain medications, and controlling diabetes. Another potential use of the technology might be to better clarify the cataract risk in patients in their 40s or 50s who are seeking LASIK surgery. Even after LASIK, when myopia returns through so-called late regression, such an instrument could clarify whether patients require LASIK retreatment or whether they are in the early stages of cataract development.

“It’s a gray area,” said John R. Wittpenn, Jr., M.D., associate clinical professor, Stony Brook University, Stony Brook, N.Y., about post-LASIK late regression. He agreed the technology could serve a valuable role in preventing unneeded and unproductive photorefractive retreatments.

Dr. Datiles said the post-LASIK assessment is one of many areas where additional research with the device is planned.

Renewed research

Dr. Wittpenn developed a similar light scatter device in the 1990s to detect early cataract changes, but his approach tracked the molecular changes through the growth in the number of large damaged proteins as cataracts develop. His research, published in the June 2000 issue of the journal Current Eye Research, developed a cataract grading system for molecular lens changes.

Although the approach identified a correlation between protein changes and cataract development, Dr. Wittpenn’s research was unable to find an absolute correlation that would apply universally.

“It’s a great technique for seeing what is going on at the molecular level, but we don’t always know what the changes mean,” Dr. Wittpenn said.

Correlating specific protein changes to timeframes for cataract development would require long-term research that follows the same patients, according to Dr. Wittpenn.

Among the other planned research is a study that examines the effectiveness of new and emerging dietary and medical treatments to halt or reverse cataract development. Such treatments are needed outside the Western world where cataract surgery remains unpredictable or unavailable, said Dr. Datiles.

“It’s a dictum in medicine that you use medical means before doing more invasive procedures,” Dr. Datiles said. Nick Mamalis, M.D., professor of ophthalmology, John A. Moran Eye Center, Department of Ophthalmology & Visual Sciences, University of Utah, Salt Lake City, agreed that a more precise way to track lens changes is needed. The technology could improve on the Lens Opacity Classification System III, which is a Food and Drug Administration-approved cataract grading method developed for clinical studies that uses lens photos to identify the stages of a cataract.

But such approaches lack the objectivity that would be needed to track the effectiveness of cataract prevention treatments.

“If we could find a way that would be able to measure the actual changes in the lens density and changes in the cataract, that would be very helpful,” Dr. Mamalis said.

Paul A. Sieving, M.D., Ph.D., director, NEI, a component of the National Institutes of Health, said in a written statement that the device could not only track the effectiveness of anti-cataract therapies but also the tendency of certain medications to cause cataract formation.

Editors’ note: Drs. Datiles, Wittpenn, Mamalis, and Sieving have no financial interests related to their comments.

Contact information

Datiles: DatilesM@nei.nih.gov
Mamalis: 801-581-6586, nick.mamalis@hsc.utah.edu
Sieving: neinews@nei.nih.gov
Wittpenn: 631-941-3363, jrwittpenn@aol.com

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