Visual acuity test:This test measures how clearly you see. Your doctor asks you to identify different letters of the alphabet printed on a chart (Snellen chart) or a screen positioned some distance away. The lines of type get smaller as you move down the chart. Each eye is tested separately. Your near vision also may be tested, using a card with letters similar to the distant eye chart. The card is held at reading distance.
Refraction assessment:Assessment of your refractive error helps your doctor determine a lens prescription that will give you the sharpest, most comfortable vision. The assessment may also determine that you don't need corrective lenses.
Your doctor may use a computerized refractor to estimate your prescription for glasses or contact lenses. Or he or she may use a technique called retinoscopy. In this procedure, the doctor shines a light into your eye and measures the refractive error by evaluating the movement of the light reflected by your retina back through your pupil.
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, to color the film of tears over your eye. This helps reveal any damaged cells on the front of your eye. Your tears wash the dye from the surface of your eye fairly quickly.