An Vision check usually involves these steps:
Part of the examination, such as taking your medical history and the initial eye test, may be performed by a clinical assistant.
This test evaluates the muscles that control eye movement. Your eye doctor watches your eye movements as you follow a moving object, such as a pen or small light, with your eyes. He or she looks for muscle weakness, poor control or poor coordination.
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. The card is held at reading distance.
Light waves are bent as they pass through your cornea and lens. If light rays don't focus perfectly on the back of your eye, you have a "refractive error." Having a refractive error may mean you need some form of correction, such as glasses, contact lenses or refractive surgery, to see as clearly as possible. 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.
You could have poor color vision and not even realize it. If you have difficulty distinguishing certain colors, your eye doctor may screen your vision for a color deficiency. To do this, your doctor shows you several multicolored dot-pattern tests. If you have no color deficiency, you'll be able to pick out numbers and shapes from within the dot patterns. If you do have a color deficiency, you'll find it difficult to see certain patterns within the dots. Your doctor may use other tests, as well.
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 any damaged cells on the front of your eye. Your tears wash the dye from the surface of your eye fairly quickly.