A Contrast sensitivity test measures your ability to distinguish between finer and finer increments of light versus dark (contrast). This differs from common visual acuity testing in a routine eye exam, which measures your ability to recognize smaller and smaller letters on a standard eye chart. Contrast sensitivity is a very important measure of visual function, especially in situations of low light, fog or glare, when the contrast between objects and their background often is reduced. Driving at night is an example of an activity that requires good contrast sensitivity for safety. Even if you have 20/20 visual acuity, you can have eye or health conditions that may diminish your Contrast sensitivity and make you feel that you are not seeing well. Symptoms of Reduced Contrast Sensitivity
If you have low Contrast sensitivity, you may have problems with night driving, including difficult seeing pedestrians walking alongside poorly lit streets. Or you might notice that your eyes tire more easily while reading or watching television. A person with normal visual acuity but poor Contrast sensitivity might see the trees in the foreground clearly (high contrast), but have trouble seeing the contours of the mountains against the sky in the background (low contrast). Poor Contrast sensitivity also can be a symptom of certain eye conditions or diseases such as cataract glaucoma or diabetic retinopathy. Changes in Contrast sensitivity also can occur after lasik, PRK and other types of refractive surgery. For example, sometimes a person who has LASIK may be able to see 20/20 after the procedure but complains of poor night vision. This could be caused by a loss of Contrast sensitivity from the surgery. Conversely, some people achieve better Contrast sensitivity and night vision after LASIK, compared with their vision with glasses or contact lenses before the procedure. In most cases, people with cataracts notice a significant improvement both in visual acuity and Contrast...
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