Impaired vision and blindness are common. About 3.4 million people in the US are blind or visually impaired.
Vision is usually measured by visual acuity charts, and normal vision is expressed as 20/20. Contrast sensitivity concerns a different but equally important part of vision. It's an essential part of visual function and is needed for everyday activities. Reduced contrast sensitivity reduces the quality of life because of the inability to drive, read, manage accounts, and travel. Your daily tasks at home are more difficult, and you are at increased risk of falls and injuries.
Paying attention to color and contrast in your home, though, can make your life safer and easier even if you have reduced contrast sensitivity.
What Is Contrast Sensitivity?
Contrast sensitivity is the ability to tell the difference between two similar colors or shades of gray. It helps you recognize an object as being separate from the background behind it. Contrast sensitivity is now considered as important as visual acuity, as it affects the quality of vision.
Visual acuity tests how sharp your vision is at a given distance and is different from contrast sensitivity. Visual acuity is tested by reading black letters against a white background (Snellen chart) in indoor conditions with bright lights. It is a high-contrast procedure designed to test the sharpness of vision at a set distance.
This test does not assess contrast sensitivity function, even though, contrast sensitivity often declines earlier in life than visual acuity. You may have reduced contrast sensitivity and poor quality of vision while your visual acuity remains normal.
Reduced contrast sensitivity can affect your work and life to a great extent. Older people with contrast sensitivity reduction are much more likely to develop dementia or mild cognitive impairment.
Reduced contrast sensitivity is associated with difficulty in driving and crashes. Crashes are more likely when both eyes are affected. Contrast sensitivity testing is now a part of vision testing for driving licensure in some European countries.
Contrast Sensitivity Loss Symptoms
Mild degrees of contrast sensitivity loss are common with aging. You may first notice it as difficulty driving in fog or rain. You may also have trouble reading when the paper color and print are not black on white. Pouring coffee into a black mug, finding a dark-colored wallet in a dark purse, and recognizing faces all become difficult as you lose contrast sensitivity in your eyes.
You may find it difficult to describe your problem. Though the visual acuity charts may show you have good sight (20/20), you may feel you aren't seeing well. You may feel that your vision is flat or misty.
Contrast Sensitivity Tests
The usual tests for vision use high contrast for reading. These tests don't measure contrast sensitivity adequately, though. Testing contrast sensitivity is done by differentiating objects of similar brightness. Some tests used are:
Pelli-Robson chart. This chart has letters of equal size but with decreasing brightness. The chart will be placed one meter away for you to read. It is quick and similar to the usual vision charts. It is useful for detecting cataracts and screening drivers for poor vision.
Vision Contrast Test System (VCTS) or Vistech. This test consists of bright and dark circles in rows and columns. The contrast reduces from left to right.
Bailey-Lovie test. This test measures both visual acuity and contrast sensitivity.
Other tests used are the Functional Acuity Contrast Test, the Cambridge test, MARS test, and the Test Chart 2000. All the tests of contrast sensitivity must be done under controlled lighting conditions as specified for each test.
Contrast Sensitivity Treatment
Reduced contrast sensitivity affects your quality of vision. Your eye specialist will first measure your contrast sensitivity and then try to find a reason for any vision loss. Some conditions like glaucoma, cataract, age-related macular degeneration, myopia, and optic neuritis can cause reduced contrast sensitivity. Treating these disorders may restore contrast sensitivity or stop its decline.
Reduced contrast sensitivity is sometimes caused by retinal disorders. Many of these, like retinitis pigmentosa and Stargardt disease, are inherited. These disorders cannot be cured, but vision may be preserved by treatment.
Severe dry eye also reduces contrast sensitivity. In such cases, artificial tears applied to provide lubrication can restore contrast sensitivity.
Color Contrast and Vision
Color and contrast can be used to make life better if you have poor vision because of reduced contrast sensitivity. Bright colors reflect the most light and are easy to see. Use solid colors like red, orange, and yellow rather than pastel colors. Also, avoid combinations such as blue, brown, and black that are difficult to distinguish with reduced contrast sensitivity.
Using colors to enhance contrast can help you live with reduced vision. Simple modifications to your home can benefit you enormously:
- Avoid patterns on stair carpets. Choose bright, solid colors. Marking the edge of each stair with a contrasting color is helpful.
- Make the edges of cabinet doors a different and bright color.
- Paint tables and chairs in bright colors to help you find them easily.
- Choose white or yellow switches on a black switchboard for visibility.
- Avoid transparent dishes and cups.
- Use a contrasting placemat under your plate to help you see the edge.
If you are struggling with vision in spite of normal vision screening, reduced contrast sensitivity may be responsible. This disorder is not detected by the usual visual acuity charts. You should go for a comprehensive eye exam by a specialist in eye diseases. They will run special tests to detect the cause of your visual difficulties and recommend ways for you to overcome them.
Contrast sensitivity loss is common and distressing. It often leads to accidents, falls, and a poor quality of life by making it difficult to read, manage accounts, and drive. Regular visits to your ophthalmologist, though, may prevent further reduction in your vision. Meanwhile, using color and contrast to improve visibility and safety is a simple and low-cost strategy for you to use at home.