A comprehensive eye exam involves a series of tests to evaluate your vision and ocular health. It is more than just getting your eyes checked for a lens prescription. It involves several tests to check your eyes for altered vision and for any eye disease. In general, it is recommended to have your eyes checked every year or two. More frequent eye check-ups would be required if you:
- Wear glasses or contact lenses
- Have a family history of eye disease or loss of vision
- Have a chronic disease that puts you at greater risk of eye disease, such as diabetes
- Take medications that have serious eye side effects
When you go for your eye examination the doctor will ask you about any vision problems you are facing or have had before and also about family history of diabetes, high blood pressure, glaucoma or macular degeneration. You should take your eyeglasses or contact lenses if using them along with you when going for the comprehensive eye examination.
The comprehensive eye examination includes a number of tests that ascertain the health, function and appearance of different parts of the eye. These include:
- Visual acuity test checks how well you can see from a distance of about 20 feet. You are asked to read aloud the letters written on a chart or screen (Snellen chart). The letters decrease in size as you read from the top line to the bottom line.
- Eye muscle test checks the function of the eye muscle used for movement of the eye. The doctor will ask you to look at a pen or any other object without moving the neck while the doctor moves it in various directions.
- Refraction test determines whether you need corrective lenses or your vision is normal. In case you need corrective lenses, it determines the prescription of the lens that will give you the best possible vision. Your doctor may use a computerized refractor or retinoscopy to determine your prescription for corrective lenses. In retinoscopy the doctor shines a light into the eye after dilation and estimates the refractive error. Then fine adjustments for the prescription are done by having you look through a variety of lenses in a mask-like device called phoropter to give you the sharpest vision.
- Pupil Testing: Your pupils control the amount of light that enters your eyes. Testing the pupils is an important part of a comprehensive eye exam. Because you do not have voluntary control of your pupils, pupil testing may uncover possible problems with your autonomic nervous system as well as other problems in the rest of your body.
- Visual field test measures peripheral or side vision. It may be done using automated perimetry in which you will be asked to look into a special instrument that flashes light. If you see the light you are asked to press a button. It may also be determined by a confrontation visual field exam in which you cover one of your eyes and look at your doctor’s hand as it moves inward and outward from your visual field. You should tell your doctor when you are able to see his hand or fingers.
- Color vision test: In this test, the doctor will show you certain multi-coloured dot patterns. In case you have a certain color deficiency you will not be able to see certain patterns on those given sheets.
- Slit lamp examination: You are asked to sit and rest your chin and touch your forehead on the slit lamp. The lamp magnifies the image of the eye and allows the doctor to look for any problems of the cornea, lens, iris and anterior chamber of the eye. Sometimes the doctor may stain the tear film of the eye with a fluorescein dye by using eye drops or by using a paper strip before examining through the slit lamp to look for cuts, foreign objects or infections of the cornea.
- Eye pressure measurement is usually done by applanation tonometry: First your eye is numbed using eye drops. The eye drops also contain fluorescein to see the tear film. Gentle pressure is applied by touching the cornea using a tonometer and eventually the amount of force required to flatten a part of the cornea temporarily is measured. The procedure does not hurt. Another method of eye pressure measurement is by using a device called iCare tonometer. It consists of a handle with a tiny white plastic ball that is brought very close to the eye. Then it taps on the cornea faster than a blink. You will only feel a quick tickle, if anything. The test does not require an anesthetic. After eye pressure measurement you doctor may decide to perform pachymetry – a special test to measure the thickness of the cornea. It uses ultrasound waves to measure corneal thickness as it is one of the significant factors that affects the intraocular pressure.
- Retinal examination is done to check for diseases of the retina or optic nerve present at the back of the eye. The doctor will try to see the back of the eye using an ophthalmoscope or slit lamp following dilation of the pupil. The doctor may also choose to do an indirect examination by using a bright light mounted on the head while each eye is kept open during examination. The eye drops used for examination will cause blurred vision and sensitivity to light for several hours after the test.
At the end of the examination your doctor will provide you the results of the tests. In case any refractive problem is detected the doctor will give you a prescription for corrective glasses or contact lenses. However if any eye disease is detected or suspected you may be asked to undergo further specific eye tests to confirm the initial finding.
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