Slit-lamp examination
A slit lamp allows the 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 provide oblique illumination of the cornea, iris and lens and of the anterior chamber. The slits allow the doctor to view these structures in cross section and detect any small abnormalities.
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When examining corneal problems, your doctor may use fluorescein dye. This dye spreads across your eyes and appears bright yellow when hit with a blue light (screened through a blue filter). This causes tiny cuts, scrapes, tears, foreign material or infections on your cornea to stand out.
Retinal examination
During a retinal examination, the eye doctor puts dilating drops in your eyes to open your pupils wide and provide a bigger window to the back of your eye. Using a slit lamp or ophthalmoscope, he or she can diagnose abnormalities in the vitreous, the retina, the optic nerve and the choroid. Important clues for the presence of disease elsewhere in the body, such as diabetes and high blood pressure, also can be detected.
Some doctors prefer to look inside your eyes with an instrument called an indirect ophthalmoscope, which uses a bright light mounted on the doctor's head, a bit like a miner's lamp. This lets them see more of the inside of your eye in great detail and in three dimensions.
Dilating drops will usually keep your pupils open for a few hours before gradually wearing off. Until then it will probably be hard for you to focus on close objects. It shouldn't affect your distance vision. With your pupils open this wide, you'll probably need sunglasses for your trip home, especially if it's a bright day. It would be safer to let someone else do the driving.
Fluorescein angiography
Fluorescein angiography is a diagnostic test commonly used for evaluating diseases of the retina and the choroid. Fluorescein, a dye also used in checking corneal abnormalities, is injected in an arm vein. As the dye circulates through your eye, the blood vessels in your retina and choroid stand out as bright yellow. A camera takes flash pictures every few seconds for several minutes. These images allow your doctor to assess damage to normal blood vessels and note the formation of abnormal blood vessels. This test is especially helpful for diagnosing and treating macular degeneration and diabetic retinopathy.
Dilated eye examination
A critical part of any eye exam is when your doctor looks at the structures inside your eyeball. Only a thorough examination of the lens and the retina allows the doctor to assess the health of your eye. Many eye disorders are virtually undetectable otherwise, before serious and often irreparable damage has occurred.
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Your doctor will put dilating drops in your eye that causes the iris to retract and open your pupil wide. Without these drops the doctor's ability to see the inside of your eyes is seriously hampered. An analogy can be made between the doctor looking through a normal-sized pupil to diagnose eye disease and you peeping through a keyhole to determine all of the contents of a room. Only by opening the door, even a crack, can you truly assess what's inside. In the same way, only by opening the pupil wide can a doctor assess the health of your eye.
Dilation is a safe procedure with few side effects other than blurry vision and sensitivity to light for a few hours until the eyedrops wear off and your pupils return to normal size. While your pupils are dilated, you may not be able to read or do closeup work. You can be prepared by bringing sunglasses with you to wear after the exam. And you can arrange for someone to drive you home. To find out more, you can check out Improve Your Eyesight Without Glasses.