Contrast sensitivity refers to the ability to see objects in terms of their size and contrast. A contrast sensitivity test will examine how your eyes function in low light and how well you can distinguish an object from a similarly colored background. The higher your contrast sensitivity, the crisper your vision will be.
What is contrast sensitivity testing?
Contrast sensitivity tests measure what eye doctors refer to as "functional vision," which is the ability to see objects that are not clearly outlined or that do not stand out from their background. During a contrast sensitivity test, patients are shown images that have different contrasting backgrounds. The images are shown under different realistic circumstances like glare. The ability to see an object in a low contrast background is scored as a contrast sensitivity function (CSF).
Reasons for contrast sensitivity tests
Contrast sensitivity testing is necessary to determine how a person functions in real-world conditions. Standard eye charts have black letters on a white background, but the real world is full of shades of gray where images blend in with backgrounds. People who have difficulty seeing distinct images under certain conditions may find they have difficulty with everything from reading to night driving.
Low contrast sensitivity may also be a symptom of eye diseases such as glaucoma, diabetic retinopathy, and cataracts. Contrast sensitivity testing can help your doctor diagnose existing eye conditions or determine whether you need special prescription lenses or laser vision correction surgery.
Performing contrast sensitivity tests
Contrast sensitivity tests are usually performed as part of a comprehensive eye exam. The test is designed to measure how well you can distinguish objects of different sizes from their backgrounds. You will be asked to wear your corrective eyewear (if you have any) during testing. Keep in mind, even if you have 20/20 vision you may suffer from low contrast sensitivity.
During testing, you are asked to look at a special chart that displays numbers, letters, dots, or any image in a sequence of increasingly lower contrast. The ability to see objects of varying size at lower contrasts is expressed as a final score.
If you are having trouble distinguishing objects from their background, you may suffer from low contrast sensitivity. Schedule an appointment with your optometrist for testing.