New System Measures Ability as Well as Acuity : Today’s Vision Test Goes Off the Chart
Calling the century-old “E” eye chart the most outmoded medical test in use, a researcher has demonstrated before 17,000 experts a new, high-tech system of determining visual ability.
In addition to measuring visual acuity more accurately than the standard Snellen chart, the Vision Contrast Test System shows a person’s ability to see under different light conditions, such as dusk or bright sunlight, Dr. Arthur Ginsburg said at the recent meeting of the American Academy of Ophthalmology.
And, the new chart can provide doctors with early information on such eye conditions and diseases as lazy eye, cataracts, glaucoma and multiple sclerosis, said Ginsburg, a biophysicist and engineer who developed the new system after 15 years of research.
“The way in which we’ve been testing vision since the Snellen chart was developed in 1862 can be compared to testing only the string section of an orchestra to determine its overall quality,” Ginsburg said in an interview.
Narrow Measurements
“The Snellen chart, the most antiquated medical test administered today, measures only a narrow band of our visual channels--it does not measure the overall quality of a person’s visual health and abilities.”
Instead of using the familiar progressively smaller black letters against a white background, the new chart utilizes a computer-composed series of circles with bars of different widths and contrasts. The bars are vertical or slant to the right or left.
“We can measure how well a person sees objects of varying sizes, such as highway signs, under varying light conditions, such as bright sunlight or fog,” said Ginsburg, a retired Air Force major who developed and conducted vision tests for Air Force pilots and space shuttle astronauts.
“The fact is people may measure 20-20 on the Snellen chart but not be able to see well enough to drive a car or fly a plane safely.”
The patient’s responses are plotted on a curve. The shape of the curve can indicate such vision disorders as cataracts, in which the normally clear lens of the eye becomes opaque; glaucoma, characterized by increased pressure within the eye, or amblyopia (lazy eye), in which the clarity of vision in one eye is below normal.
May Save Sight
Catching these disorders in time may save a patient’s sight, said Ginsburg, founder and director of the Air Force Aviation Vision Laboratory at Wright-Patterson Air Force Base in Ohio.
Similarly, the test can be an early detector of such general diseases as multiple sclerosis and diabetes since vision-related symptoms of these illnesses often appear at an early stage. The Snellen test does not detect these symptoms, Ginsburg said.
One-thousand of the new tests, produced by Vistech Consultants Inc., have been sold since July, 1984.
The system has been adopted as a vision test by Lighthouse for the Blind and Project Orbis. It is also being used by transportation researchers to study how such factors as glare from automobile windshields and spray from trucks on wet roads affect driver safety.
