Tests Better Measure Vision in Blinding Diseases

Blinding eye diseases test for retinitis pigmentosa

/ Author:  / Reviewed by: Joseph V. Madia, MD

(RxWiki News) When it comes to patients with eye diseases that lead to blindness, it can be difficult to detect low levels of remaining vision That determination is generally made through subjective tests such as detecting hand motion.

A pair of computerized tests, however, show promise for detecting the amount of remaining vision in patients with blinding eye diseases including retinitis pigmentosa, an eye disease caused by damage to the retina that can lead to blindness.

The new tests can detect visual acuity below the current limit of deduction using standard tests. It could prove helpful in assessing new treatment options for severe vision loss such as artificial retinas.

"Visit an optometrist if having sight issues."

Dr. Ava K. Bittner, an optometrist with Johns Hopkins University and lead study researcher. said that computer-driven grating tests appear to be reliable and capable of evaluating vision that may fall outside the range of standard clinical tests.

The new tests — the Grating Acuity Test and Grating Contrast Sensitivity test — evaluate the ability of  patients to see the direction and contrast in a black-and-white, or gray and white striped "grated" pattern.  During the tests, patients view grated patterns on high-definition LCD screens. They are then asked to indicate the direction of the stripes by pushing buttons.

During the study the tests were assessed in 20 patients who were legally blind from retinitis pigmentosa or other retinal diseases. Researchers found that the tests could detect lower levels of remaining vision compared to standard tests because the grated patterns were more easily recognizable than letters.

The testing could detect vision as low as 20/4000 as compared to the 20/1600 detected with current low-vision letter tests.The tests were found reliable after repeated testing, and more easily quantified since the tests were not subjective.

The tests were developed for use in clinical trials of the Artificial Silicon Retina, a computer chip implant that could help restore useful vision in patients with severe vision loss from retinitis pigmentosa. Since the treatment could be risky, they will first be tested in patients with little remaining vision to lose.

Dr. Christopher Quinn, an optometrist with Omni Eyes Associates, said such tests would be somewhat useful in a limited set of patients with severe vision loss to better document the extent of that loss.

"Certainly as a tool in researching treatments, it is always nice to have a validated and objective measure to compare results," he said.

The research was published in the October issue of Optometry and Vision Science, official journal of the American Academy of Optometry.

Reviewed by: 
Review Date: 
October 3, 2011
Last Updated:
October 3, 2011