Low contrast sensitivity tests and treatments

Sunday, October 25th, 2009 at 1:19 pm Post in Eye Exams and Vision Screening

Good vision such as 20/20 does not mean satisfying contrast sensitivity. Common vision tests using black letters or numbers displayed against white backgrounds can not reflect your exact contrast sensitivity, since the real world is filled with grey shades. So that special contrast sensitivity testing is necessary.

May eye diseases or conditions may cause poor contrast sensitivity, such as cataracts, glaucoma, and diabetic retinopathy, as well as the side effects from LASIK and PRK. People with low contrast sensitivity may have difficulty in some conditions, such as seeing traffic lights, spot other cars and pedestrians during night driving. Since these people have poor perception of objects that do not stand out from their backgrounds, they may even stumble when they fail to see similarly colored pavements.

The term “contrast sensitivity function” (CSF) is used to describe people’s low contrast seeing ability. A contrast sensitivity test may be included in a routine screening after the visual acuity test, which measures the ability of seeing detailed letters or numbers. With your eyeglasses or contacts lenses wearing on, your eyes will be tested in together by a low-contrast test chart, which consists of bars and dots in different colored contrasts that are used to evaluate the patient’s exact CSF. Your CSF will certainly be affected by the sizes of objects: the larger the objects are, the higher CSF you can achieve.

By testing your eyes using bar and dot patterns displayed against varying contacts or intensities, your highest and lowest contrast sensitivity can be determined and plotted into a curve, which shows your contrast sensitivity readings. Tests under both bright and dark conditions can provide more detailed information about your images process capability.

As a volunteer, you can get a contrast sensitivity test as a necessary part of the evaluation of new ophthalmic devices such as LASIK excimer lasers and new intraocular lenses required by FDA. Once you are diagnosed with low contrast sensitivity, some remedies are available, depending on the source of the problem. Usually, artificial lenses with a yellow filter can improve contrast. If the low contrast sensitivity is caused by higher-order aberrations, wavefront lenses or LASIK are the right choices. Another option is intraocular lenses with yellow tints, which can also offset low contrast sensitivity.