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Tests and diagnosis
By Mayo Clinic staffThe only way to know for sure if you have a cataract is to have an eye examination that includes several tests:
- Visual acuity test. Acuity refers to the sharpness of your vision or how clearly you see an object. In this test, your eye doctor checks to see how well you read letters from across the room. Your eyes are tested one at a time, while the other eye is covered. Using a chart with progressively smaller letters from top to bottom, your eye doctor determines if you have 20/20 vision or less acute vision.
- Slit-lamp examination. A slit lamp allows your eye doctor to see the structures at the front of your eye under magnification. The microscope is called a slit lamp because it uses an intense line of light — a slit — to illuminate your cornea, iris, lens and the space between your iris and cornea. The slit allows your doctor to view these structures in small sections, which makes it easier to detect any small abnormalities.
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Retinal examination. In this procedure, your eye doctor puts dilating drops in your eyes to open your pupils wide and provide a bigger window to the back of your eyes. Using a slit lamp or a special device called an ophthalmoscope, he or she can examine your lens for signs of a cataract and, if needed, determine how dense the clouding is. Your eye doctor will also check for glaucoma and, if you have blurred vision or discomfort, check for other problems involving the retina and the optic nerve.
Dilating drops usually keep your pupils open for a few hours before their effect gradually wears off. Until then, you'll probably have difficulty focusing on close objects, while your distance vision is generally less affected. With your pupils open this wide, you may want sunglasses for your trip home, especially if it's a bright day. Also, it may be safer to let someone else do the driving.
If you have a cataract, you can discuss treatment options with your eye doctor. If — in addition to having a cataract — you have other eye conditions that limit your vision, such as macular degeneration or advanced glaucoma, removing the cataract may not improve vision, and cataract surgery may provide disappointing results.
