Many people find out while they are still young that they have some type of visual blindness, but if you have never visited an eye doctor he or she will use several tests during an eye exam to determine if you have one of three types of blindness. Here are the different tests used and the three types of blindness your eye doctor will attempt to diagnose or rule out.
The Ishihara Test and Colorblindness
About seven percent of the total population cannot see certain colors due to a defect in their color cones and rods of the retina. To determine if you have this type of colorblindness, your eye doctor will utilize the "Ishihara test." The Ishihara test consists of thirty or so plates, made up of colored dots. The dots are varying colors and shades of red, blue, green, yellow, and orange. In the middle of each plate are different numbers created by a different set of colored dots. Your eye doctor will show you several plates to determine if you are able to see all of the numbers in the middle of each plate.
Some of these are very tricky in that the color variations between the surrounding dots and the dots that make up the numbers are so slight it might be hard to tell. If there are any plates where you cannot see the numbers in the middle at all, it reveals that you do have a form of colorblindness. While there is no cure for it, there is visual therapy to help you identify other important objects you may not see well (such as red or green traffic lights).
Legal Blindness in One or Both Eyes
Part of every eye exam requires you to look at a lighted screen that is twenty feet away. This helps determine if you have normal vision (20/20 sight looking at something twenty feet away) or if your vision needs correction. If you cannot see the letters or numbers on the lighted screen at all, your eye doctor will use the corrected vision magnifier to find out what power your corrective lenses need to be. This device looks like a giant pair of metal goggles on a swing arm and fits over the bridge of your nose. Your eye doctor will check one eye at a time, and if he or she determines that either eye is 20/600 or worse, you are legally blind in that eye.
It is very hard to miss total blindness for most of your life. You absolutely cannot see anything and everything is totally dark. While your eye doctor, one like Las Vegas Family Eye Care, does not need to perform an exam to diagnose this, he or she can perform tests to find out why you are totally blind. It may even be possible to reverse some total blindness if it is caught early in life or if it is sudden after a lifetime of being able to see reasonably well. This is why it is so important to have your eyes examined regularly and always seek immediate medical help if you suddenly cannot see.