I’ve never had an eye examination. What is involved?

Apr 08, 2018 Dr Karen Persram, Features / Columnists

The eye is often compared to a camera that takes an image of what you see, but the process is much more involved. When you look at something, the light rays from that object being viewed hit the front of the eye, the cornea, where they are refracted (bent).
The light rays then hit the lens where further bending occurs and then they travel through the vitreous and hit the retina, which is the inner layer of the eye. The light is then converted to electrical nerve impulses by the rods and cones which make up the retina. These travel via the optic nerves to the part of the brain responsible for vision.
If any of these structures is abnormal or defective, vision can be affected. As part of a normal eye examination, the optometrist checks all of these structures to determine the health/visual status of the eye.
First, the optometrist will check your visual acuity (how well you are seeing) to see where it is compared to 20/20. They will cover first one eye, then the other, and see how far down a vision chart you can see. Next, they will do a test called a cover test to see if the eyes are straight and aligned, and not turned or crossed. The cover test will pick up what Guyanese call “cock eye” or “cross eye”. Then, they will use an instrument called a retinoscope to determine the prescription needed (if any) for you to see clearly.
Some offices will use an auto-refractor machine to do this part of the eye exam. The optometrist will then use a phoropter (the machine with all the lenses in it that comes in front of your eyes- the one in front of the patient’s eyes in the cartoon) to further refine the data from retinoscopy by giving you choices of lenses and you decide which gives you the best vision. This is where the doctor usually asks which lens is better, one or two.
Next, they will use a keratometer to measure the curvature of the cornea, which is the front surface of the eye. In a disease called keratoconus, this measurement is steeper than normal.
The optometrist will then use an instrument called an ophthalmoscope to look through the pupil, the black hole in the center of the iris (colored part) and examine the inside of the eye. They will check to ensure that the vitreous gel which fills the eyeball, and the retina, the inner back layer, are both healthy. They will check to make sure that the cupping of the optic nerve is within normal limits. If it is larger than normal, it can be an indication of glaucoma. They will check to make sure the blood vessels are not enlarged or leaking, which can happen as a complication of diabetes.
They will check the macula, which is the part of the retina we use for central vision to make sure the pigment there is even and not disturbed, and if there are spots called drusen, which can signal macular degeneration.
Next, they will use a slit lamp biomicroscope to examine the anterior structures of the eye: the tear film, the anterior chamber, the cornea , and the lens. They will make sure that all of these structures are clear and healthy. Then, they will measure the intraocular pressure of the eye. This test is one of the ones used to diagnose glaucoma.
None of these tests are painful or invasive. You should have no fear of checking your eyes.
IF I SEE CLEARLY, DO I STILL NEED AN EYE EXAMINATION?
Even if you don’t have a problem with your vision, regular checkups should be part of your normal health care routine. Comprehensive eye examinations should be made by an optometrist every one to two years to maintain healthy eyes and vision.
For example, patients with glaucoma don’t usually have any symptoms and most are diagnosed during a regular eye exam. Patients with diabetes should have more frequent eye exams as they can get bleeding within the eye that they are not aware of. With both glaucoma and diabetic retinopathy (bleeding in the eye), early treatment can save/prolong vision.
For more information , or if you wish to suggest a question, please contact Dr. Karen Persram at 295 Quamina Street, Georgetown. Tel: 225-0605, or send emails to drkpoffice@gmail.com.

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