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Slit-lamp examination
A slit lamp is a microscope that magnifies and illuminates the front of your eye with an intense line of light. Your doctor uses this device to examine the eyelids, lashes, cornea, iris, lens and fluid chamber between your cornea and iris.
Your doctor may use a dye, most commonly fluorescein (flooh-RES-een), to color the film of tears over your eye. This helps reveal damaged cells on the front of your eye. Your tears wash the dye from the surface of your eye fairly quickly.
A man undergoing indirect ophthalmoscopy
Indirect ophthalmoscopyOpen pop-up dialog box
Retinal examination
This examination — sometimes called ophthalmoscopy or funduscopy — allows your doctor to evaluate the back of your eye, including the retina, the optic disk and the retinal blood vessels that nourish the retina. Having your pupils dilated with eyedrops before the exam keeps your pupils from getting smaller when your doctor shines light into the eye.
After administering eyedrops and giving them time to work, your eye doctor may use one or more of these techniques to view the back of your eye:
Direct exam. Your eye doctor uses an ophthalmoscope to shine a beam of light through your pupil to see the back of the eye. Sometimes eyedrops aren’t necessary to dilate your eyes before this exam.
Indirect exam. During this exam, you might sit up or be reclined in the exam chair. Your eye doctor examines the inside of the eye with the aid of a condensing lens and a bright light mounted on his or her forehead. This exam lets your doctor see the retina and other structures inside your eye in great detail and in three dimensions.
A man undergoing applanation tonometry test
Applanation tonometryOpen pop-up dialog box
Screening for glaucoma
Tonometry measures the fluid pressure inside your eye (intraocular pressure). This is one test that helps your eye doctor detect glaucoma, a disease that damages the optic nerve.
Several methods to measure intraocular pressure are available, including:
Applanation tonometry. This test measures the amount of force needed to temporarily flatten a part of your cornea. You’ll be given eyedrops with fluorescein, the same dye used in a regular slit-lamp examination. You’ll also receive eyedrops containing an anesthetic.
Using the slit lamp, your doctor moves the tonometer to touch your cornea and determine the eye pressure. Because your eye is numbed, the test doesn’t hurt.
Noncontact tonometry. This method uses a puff of air to estimate the pressure in your eye. No instruments touch your eye, so you won’t need an anesthetic. You’ll feel a momentary pulse of air on your eye, which can be startling.
If your eye pressure is higher than average or your optic nerve looks unusual, your doctor might use a pachymeter, which uses sound waves to measure the thickness of your cornea. The most common way of measuring corneal thickness is to put an anesthetic drop in your eye, then place a small probe in contact with the front surface of the eye. The measurement takes seconds.
You might need more-specialized tests, depending on your age, medical history and risk of developing eye disease.