Tests That Can Safeguard Your Sight
As medical checkups go, eye exams are relatively stress-free. You can keep your clothes on, no needles are involved and you won’t be asked to step on a scale! And the benefits—ensuring the health of your eyes and the sharpness of your vision—make the exam well worth it. During your visit, your ophthalmologist will decide which tests to do based on your vision concerns, your age and your medical history. Here’s how he’ll gauge the health of your eyes.
Visual acuity test
What it tests: How clearly you see at a distance.
How it works: You will be asked to read letters of various sizes on a chart. Or you may view a chart inside a machine. The type gets smaller as you move down. The smaller the type you can see, the better your vision is. Your score will be compared with how someone with optimal vision sees at that distance.
What it tests: The alignment and movement of your eyes. Strabismus, for example, is diagnosed when eyes aren’t properly aligned or don’t move together when focusing. This test is also used to screen for other eye-movement disorders.
How it works: You’ll be asked to track a moving target, such as a hand or a pen. As your eyes travel up and down and from side to side, your healthcare provider checks whether they are aligned.
Schirmer tear test
What it tests: The moistness of your eyes.
How it works: Your doctor places extremely thin strips of blotting paper under your lower eyelids.
After a few minutes, the doctor checks how much of the strip is saturated with tears.
Slit lamp exam
What it tests: The presence of dry eye, cataracts, macular degeneration, diabetes complications, corneal scratches or infections.
How it works: A microscope with a thin beam of light is used to examine each eye. You may also receive eyedrops to dilate your pupils. The eyedrops take about 15 minutes to work and may sting briefly. After the exam, your eyes will be more sensitive to light, and your near vision will be blurred until the dilating drops wear off.
What it tests: The pressure inside your eyes, which increases if you have glaucoma.
How it works: First, the doctor uses special eyedrops to numb your eyes. Then he or she may also add a squirt of orange dye to make it easier to view your cornea. Using a little probe on a slit lamp, the doctor gently presses on each cornea to measure eye pressure. It doesn’t hurt, and the numbing drops wear off in about 20 minutes.
Corneal staining test
What it tests: The smoothness of your cornea. This test is administered to someone who’s had an abrasion, an infection, dry eyes or blurred vision.
How it works: An orange dye is placed on the surface of your eye using a dropper or a moistened strip containing the dye. Your healthcare provider then examines the surface of your eye with a microscope that emits blue light.
What it tests: The strength of any prescription you may need to enhance your vision
How it works: You will look into a mask-like device called a phoropter, which holds lenses of various strengths. As you focus on an eye chart, your doctor will flip two lenses into your view and ask if the letters are more or less clear. By repeating this step with different combinations, the doctor can pinpoint the power that gives you the best possible vision.
Visual field exam
What it tests: Your field of vision. It checks for blind spots due to glaucoma, retinal problems, a stroke or other ailments.
How it works: You’ll cover one eye and stare straight ahead with the other. You may watch a screen as dots of light flash. Usually, you’ll press a button each time you see a dot, enabling a computer to map your field of vision.
Getting the results
After an eye exam, your doctor will go over the findings with you, alert you to any risks and suggest steps to protect your vision. If your current glasses aren’t doing the trick anymore, you’ll get a prescription for new ones. If you need new contacts, you’ll need a contact lens fitting. If other eye problems are detected, your doctor may advise further tests and/or explain treatment options, which may include eyedrops, medication or other therapies.