What Is Vision Testing?
Vision testing is a more comprehensive set of eye tests than simple vision screenings and is performed by an eyecare professional in a controlled office setting with vision testing equipment that goes far beyond what's available at a typical vision screening.
Often performed with eye drops that help the pupil "open up" (dilation), these tests commonly include testing of vision at multiple distances, peripheral vision testing, and a series of procedures designed to check the structures of the eye for evidence of eye disease or eye problems like age-related macular degeneration, glaucoma, cataracts or diabetes.
Many of the conditions and diseases that may not reveal themselves at a vision screening can be discovered under the close professional observation of a vision test. Only an eyecare professional can direct you to the treatment necessary to improve your vision or protect your eyes – from a prescription for corrective lenses, to medication to a wide variety of surgical options now available to people with eye problems.
Types Of Vision Tests.
In general, vision testing includes vision testing equipment and procedures that either measure or gauge your visual ability, or look closely at specific structures of the eye.
- Visual acuity testing: The Snellen Chart (the chart with the big E at the top) is used to test each eye for visual acuity or "sharpness" at a distance. A smaller, hand-held chart is used to test short vision.
- Visual field testing: Manual and automatic testing designed to measure the quality of your side vision (peripheral vision). This type of test usually involves covering one eye and focusing the other on a fixed point in front of you, while describing what you can see on the "periphery" of your vision.
- Cover testing: By having you focus on a distant object within a room, and then alternately covering each eye, your eyecare professional can see if your eyes work together, or must refocus slightly.
- Colour-blind testing: Using a series of multi-coloured dots arranged within a circle, colour-blind vision testing "hides" numbers within the overall pattern of dots. These numbers will appear as easy-to-see coloured numbers to everyone except those few people who suffer from various degrees of colour-blindness – the inability to perceive certain colours or colour combinations.
- Refraction testing: Refraction errors like shortsightedness and longsightedness are the most common eye problems. Vision testing is used to determine how strong your prescription glasses must be to see clearly, based on how your eyes react while using the vision testing equipment.
- Phoropters are machines that allow your eyecare professional to "switch" lenses during your exam to see if your focus is better, or worse.
- Autorefractors are machines that automatically check the lens power needed to clearly focus images on your retina for the best possible vision.
- Slit lamp testing: This piece of vision testing equipment combines a simple chin rest with a light source that produces a "slit" of light that's used to scan your eye. Your eyecare professional (with the help of special viewing lenses) can look into the internal structure of your eye to potentially diagnose a host of eye problems and diseases.
- Ophthalmoscope: this is the small hand-held device that is used to examine the inside of your eye. The light allows your eyecare professional to see such structures as the retina and the optic nerve.
- Retinoscope: this lighted instrument shines a light into your eyes. The angle of reflection off of your retina is measured and gives your eyecare professional a measure of how far off your vision may or may not be.
- Tonometry (Glaucoma) Testing: There are two types of glaucoma vision testing, each with the goal of measuring the internal pressure of the eye. Increased eye pressure is a warning sign for glaucoma, a series of eye diseases that damages the optic nerve of the eye, limiting and sometimes eliminating vision.
- The "Puffer" Test: A light is beamed into your eye while a gentle puff of air is blown across the eye's surface. A special machine measures the resistance of the eye to the puff of air, and then calculates internal eye pressure.
- The Touch Test: Using a machine called an applanation tonometer, a special probe makes gentle contact with the eye's surface to measure internal eye pressure. Your eyecare professional may numb your eye in advance.
- Dilation testing: Sometimes, your eyecare professional will use special drops to "open up" your pupil (dilate it) so that as much light as possible can enter the eye. Using special magnifying lenses and other vision testing equipment, your eyecare professional can diagnose a host of eye problems and see internal structures that indicate the presence of eye diseases.
Vision testing is both thorough and painless, though there may be some momentary discomfort from direct beams of light as a result of dilation. New technologies like the Optomap can be used instead of dilation, depending upon the specific vision testing being specified by your eyecare professional.
How Often Should I Get A Vision Test?
As a general rule of thumb, it's a good idea to have a comprehensive eye exam and vision test at least every two years. This especially includes children below the age of 5, who may not fully understand that they're even having a vision problem until they undergo a professional vision test And since vision can change rapidly throughout childhood, regular vision testing is a quick and smart way to keep up with those changes.
The information seen here is for reference purposes only and is not intended as medical advice or to diagnose or prescribe any specific treatment(s). For all questions and concerns about your vision, eye health and potential eye problems, please consult an eyecare professional.
Special thanks to the National Eye Institute, National Institutes of Health, for source material that aided in the creation of this website. Visit the NEI/NIH website.