When visiting the eye doctor, it is important to remain well informed about your eyesight and the eye exam procedures. The better informed you are about the eye exam, the more capable you will be to make educated decisions and to keep yourself on the right road to good eye health. A part of being informed means asking the eye doctor specific questions and understanding the meaning of their answers.
1. What is my Visual Acuity?
Your visual acuity is how clearly or sharply you are able to see objects at a distance. Typically, eye doctors will also you to read letters and even numbers from an eye chart, which will be positioned 20 feet away. As the lines draw nearer to the bottom of the chart, the size of the letters and numbers gets smaller. Visual acuity is measured as a fraction based off this chart.
Ã¢â‚¬Å“PerfectÃ¢â‚¬Â vision is generally considered 20/20. The top 20 refers to the distance you are away from the eye chart. The bottom number is the distance a person with Ã¢â‚¬Å“normalÃ¢â‚¬Â eyesight could read the same line as you. For example, if your visual acuity is 20/20, that means you can see objects clearly from a distance of 20 feet that a person with normal vision could see from 20 feet.
If, however, your visual acuity is 20/60, the line you can read correctly from a distance of 20 feet is the same as the line a person with normal vision could read from 60 feet away.
2. How is my Visual Field?
Yours visual field is the space in front of you that you are able to see without moving your eyes. The doctor can use a few different tests to determine your visual field. One test is the confrontation visual field exam.
With this exam, the doctor sits in front of you and asks you to cover one eye. As you look directly at the doctor, he or she tests your visual field by moving his or her hand in and out of the area. You then tell the doctor when you are able to see his or her hand.
Another way the doctor may test your visual field is to ask you to sit a short distance away from a screen and to stare at its center. You then tell you doctor when you see an object move into your visual field. With the automated perimetry, the doctor uses a computer program to flash small lights while you look into a special instrument. You then push a button when you see the lights.
No matter which test your doctor uses, the purpose is the same to create a map of your peripheral vision. If you have problems in this area, the doctor will work to determine why your range of peripheral vision is limited.
3. How is my Corneal Health?
Your doctor will also perform a test called a refraction assessment. Refraction is how light waves bend as they pass through your cornea and your lens. This assessment helps the eye doctor determine the type of corrective lens prescription you need in order to achieve the sharpest vision. If you do not need to wear prescriptive lenses, however, you will not undergo this test.
In order to perform the test, the eye doctor might use a computerized refractor. This measures your eyes and estimates the prescription necessary to correct your vision. The doctor might instead choose to use a test called retinoscopy. With this exam, the doctor will shine a light into your eye in order to measure the refractive error in your eye. To help pinpoint your refractive error, the eye doctor will likely have you look through a mask-like device called a Phoroptor. The differing lenses in this device help the doctor find the right combination to give you the sharpest vision. He or she will repeat this procedure several times until the right combination is found.
4. Is my Retina Healthy?
Your doctor will also perform a retinal examination, which is sometimes called a fundoscopy or ophthalmoscopy. With this exam, the eye doctor will examine the back of your eye. This includes the retina, as well as the choroids, the optic disc, and the blood vessels. For this exam, the doctor may dilate your pupils, which makes them open up and become bigger, with special eye drops. The doctor may shine a beam of light into your pupils or he or she may have you recline and look into your eyes while wearing a bright light on his or her forehead.
5. Should I worry about Glaucoma?
Another part of the routine eye exam is a glaucoma examination. Glaucoma can cause problems with vision, even blindness. In addition, it often does not have any symptoms. Therefore, regular tests are the only true way to monitor its development. The doctor may use an applanation tonometry exam to test for glaucoma.
With this test, the doctor places orange dye in the eye to assist with viewing the cornea. He or she then tests the amount of force needed to temporarily flatten your cornea. This test requires an anesthetic. The noncontact tonometry exam, on the other hand, does not require an anesthetic. Instead, a puff of air is forced onto the eye to test the cornea.
Image: courtesy Wellcome Images, Creative Commons