An ophthalmologist’s tips for vision testing
It doesn’t require an ophthalmologist to give a vision test as part of a work fitness exam. Anne Sumers, MD, FAAO, an ophthalmologist in Ridgewood, NJ, says occupational health specialists "should feel absolutely confident" about giving vision exams.
To help you in your practice, Sumers offers some pointers. One suggestion she makes: You should always consider giving a visual acuity test the standard eye chart exam any time a worker’s vision could be a safety issue. Even if the regulations do not require the visual acuity test, it is a good idea to conduct one if the regulations require a color blindness test or if you just know that vision is a safety issue.
Sumers notes that the engineer in the Secaucus train wreck had remarkably poor visual acuity, 20/400 in one eye even with correction. If the occupational medicine physician had realized that, he may have been alerted to a safety problem even before testing for color blindness.
"That engineer couldn’t have gotten a driver’s license in New Jersey," Sumers notes. "If you’re worried about vision at all, you ought to start with the visual acuity."
The exact type of visual acuity or color perception test is not of great importance, Sumers says. The occupational health physician involved in the train wreck used the Dvorine tests, but the test more commonly used by ophthalmologists is Ishihara’s test for color blindness. The brand name of the test is of little importance, but Sumers stresses that you must follow the instructions that come with the test.
Both Dvorine and Ishihara provide color plate tests suitable for testing color perception, but companies also supply some test materials (such as a simple color wheel) that would be insufficient for safety-sensitive testing.
Any medical supplier can provide the testing materials and the appropriate instructions for use. Sumers offers this other advice from her own experience:
• Be sure the physical parameters of the test are correct.
The visual acuity test is given with the patient standing exactly 20 feet away from the eye chart. Measure the distance; don’t just estimate it. And check to see the patient has not stepped forward or backward during the test.
• Make sure one eye really is covered, when appropriate.
Do not underestimate how much people will attempt to cheat. Even children will peek out with their good eye when it is supposed to be covered, and adults trying to save their jobs have a lot more motivation.
• Do not allow patients to memorize the test.
Sumers tests the vision of the entire Giants professional football team, and she recalls one day when she and her staff were lax with the testing procedure.
A long line of football players was lined up to have their visual acuity tested, and in the middle of one player’s exam, someone accidentally leaned against the light switch and the room went dark. But the patient continued reading the eye chart correctly.
"He said, Well, I’ve heard it 20 times,’" she recalls. "It wasn’t life or death for them, but they were motivated to stay on the field."
The same problem can occur with color perception tests. If you use the same testing materials all the time, or if you use common materials that the patient may have seen elsewhere, the patient can just call out the correct series of answers. If you suspect memorization, try altering the sequence of the color plates or asking the patient to read the visual acuity lines out of order. You also can use an entirely different test, as long it still is appropriate for the testing goal.
• Ask about corrected vision.
All vision testing should be conducted with the patient’s best corrected vision. That means the patient should wear whatever contacts or eye glasses that would help the most, whether they are bifocals, reading glasses, or others. Always ask about corrected vision because patients often will not volunteer that they normally wear lenses. Many patients, in fact, have the mistaken belief that vision testing is intended to be done without correction.
• Use good lighting.
With poor lighting, even people with perfect vision often will fail color perception tests. Strong, even lighting is necessary, and some vision testing materials will provide specific guidelines for what sort of lighting is necessary.
• Do not use faded color perception tests.
While this may seem obvious, it happens. Sumers recalls that she once worked in a facility in which it seemed every patient who came through was colorblind.
Before long, the staff realized the color perception plates were old and had faded so that no one could distinguish the colors. In particular, do not leave color perception plates exposed to light, which hastens discoloration.
You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
- Award-winning Medical Content
- Latest Advances & Development in Medicine
- Unbiased Content