Low contrast sensitivity tests and treatments
People’s visual system is consisted of several integral parts. While peripheral vision and central vision form in together vision field, some elements are generally irrelevant to each other. For instance, good vision such as 20/20 does not mean satisfactory contrast sensitivity, which is now a big problem bothering a lot of people. And common vision tests using black letters or numbers displayed against white backgrounds can not reflect one’s exact contrast sensitivity, since the real world is filled with grey shades. As a result, a special test for contrast sensitivity is necessary.
The consequences of suffering low contrast sensitivity
People with low contrast sensitivity always experience difficulty in some conditions, such as seeing traffic lights and spotting other cars or 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.
Possible reasons for poor contrast sensitivity
Some eye diseases may cause poor contrast sensitivity, such as cataracts, glaucoma and diabetic retinopathy. People with any one of these diseases will suffer serious loss of visual acuity and contrast sensitivity. Moreover, contrast sensitivity can also be affected by some other factors, e.g. the side effects following LASIK and PRK surgeries.
Details of CSF test
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 eye checkup after the visual acuity test, which measures the ability of seeing detailed letters or numbers. Wearing eyeglasses or contact lenses if necessary, the patient’s eyes will be tested in together by a low-contrast test chart. In detail, a set of bars and dots in different colored contrasts are used to evaluate the patient’s exact CSF. Of course, one’s CSF will be affected by the sizes of objects. The larger the objects are, the higher CSF people can achieve.
Where to get such a test for free?
By testing the eyes using bar and dot patterns displayed against varying contrasts or intensities, people’s highest and lowest contrast sensitivity can be determined and plotted into a curve, which represents the contrast sensitivity readings. Furthermore, tests under both bright and dark conditions can provide more detailed information about people’s capability of processing images. As a volunteer, it is possible to get a free contrast sensitivity test as a necessary part of the evaluation of new ophthalmic devices, such as LASIK excimer lasers and new intraocular lenses. This kind of evaluation is strictly required by FDA.
Some remedies for low contrast sensitivity
Once diagnosed with low contrast sensitivity, it is a necessity to get some remedies, depending on the specific reasons of the problem. In most cases, artificial lenses with a yellow filter can be used to improve contrast during objects viewing. If low contrast sensitivity is caused by higher-order aberrations, wavefront lenses or LASIK is the right choice. Another option is intraocular lenses with yellow tints, which can also offset low contrast sensitivity.