Q&A for General Knowledge about Eyes

Questions:

1. Does 20/20 mean perfect vision?

2. What is vision requirement for driving in California?

3. What is the doctor looking for during an eye exam?

Answers:

1. Does 20/20 mean perfect vision?

20/20 vision is a term used to express normal visual acuity (the clarity or sharpness of vision) measured at a distance of 20 feet. If you have 20/20 vision, you can see clearly at 20 feet what should normally be seen at that distance. If you have 20/100 vision, it means that you must be as close as 20 feet to see what a person with normal vision can see at 100 feet.

20/20 does not necessarily mean perfect vision. 20/20 vision only indicates the sharpness or clarity of vision at a distance. There are other important vision skills, including peripheral awareness or side vision, eye coordination, depth perception, focusing ability and color vision that contribute to your overall visual ability.

Some people can see well at a distance, but are unable to bring nearer objects into focus. This condition can be caused by hyperopia (farsightedness) or presbyopia (loss of focusing ability). Others can see items that are close, but cannot see those far away. This condition may be caused by myopia (nearsightedness).

A comprehensive eye examination by a doctor of optometry can diagnose those causes, if any, that are affecting your ability to see well. In most cases, your optometrist can prescribe glasses, contact lenses or a vision therapy program that will help improve your vision. If the reduced vision is due to an eye disease, the use of ocular medication or other treatment may be used.

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2. What is vision requirement for driving in California?

The minimum licensing vision requirement for driving in California is best corrected visual acuity(VA) to be 20/200 or better in at least one eye, which is verified by an optometrist(eye doctor). The DMV will not issue a driver license and/or the driving privilege will be revoked if the minimum requirement is not met. Presently, there is no minimum requirement in peripheral vision. Driving restrictions may be implemented for those drivers with best corrected visual acuity(VA) 20/40 – 20/200 and/or loss of peripheral vision and/or progressive eye disease affecting vision.

For commercial drivers, the federal standard requires best corrected visual acuity to be 20/40 or better.

California Vehicle Code(CVC) 12804.9 (a) (1) (E) is the departmental authority for administering the vision exam. CVC 12805 is the authority to refuse issuance or renewal of a driver license for not meeting minimum visual acuity licensing standard. The DMV uses 2 methods of vision testing: Snellen chart and Optec 1000 Vision Tester.

The Snellen chart contains 5 lines of letter with decreasing letter size at standardized 20 feet. The Optec 1000 Vision Tester uses an instrument to simulate the Snellen chart at 26 feet.

Applicants who do not pass either exam and/or suspected vision problems will often be referred for a vision evaluation. The form DL62 will often need to be completed by the doctor establishing the driver’s baseline vision and changes that can be made to improve the driver’s vision.

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3. What is the doctor looking for during an eye exam?

Have you ever wondered what your eye doctor is actually looking for when (s)he examines your eyes?  The answer is that an eye exam is not just a new pair of glasses or contact lenses; because your eyes are the windows to your general health and are valuable for disease detection and management, the doctor is looking for any indication of significant changes in the different parts of the eye, so that (s)he can diagnose conditions or diseases that might require treatment.

Here’s a breakdown of the eye and how an eye doctor examines it for conditions or diseases that might affect vision.

Eyeball: Your doctor may use one of many different tests to measure pressure inside the eyeball. The air ‘puff test’ – an instrument that uses a puff of air in each eye – can accurately measure your eye pressure. Excessive pressure is often a sign of glaucoma, which can lead to blindness. If detected early, the condition can be managed with medications or surgery.

Cornea: Made up of clear tissue that covers the colored part of the eye, or iris, the cornea is the eye’s outer lens. It helps the eye to focus on distant objects. But if the cornea contains anatomical irregularities, the result can be nearsightedness or farsightedness. These errors can be corrected with glasses or contact lenses. Another potential condition is corneal arcus (a yellowish or whitish ring around the cornea), which often is an indication of high cholesterol. If this happens your eye doctor may suggest you to visit your primary care doctor for diagnosis and treatment.

Natural Lens: As we age, the lens within each eye can become yellow and cloudy, producing a cataract that affects vision. Cataracts can cause your prescription to change and must be managed until it is time to remove them through surgery.

Optic Nerve: Discoloration, depression or swelling of the optic nerve – which connects the eye to the brain – can indicate the presence of glaucoma, hypertension or even a brain tumor. In many cases, therapy that includes medications and even surgery can stabilize or improve all three conditions if diagnosis occurs early enough.

Retina: This is the light-sensitive layer of cells inside your eye that is crucial to vision. Your eye doctor will check the retina carefully to see if aging has damaged the macula, a key area of tissue. If aging has damaged has occurred, it may be the result of age-related macular degeneration, which can cause blindness. The condition can’t be cured, but often it can be slowed down if diagnosed early. The key is early detection and management by your eye doctor.

Eye doctors also study the retina carefully for signs of prediabetes and diabetes, looking for blood vessel leakage or hermorrhages that could signal the presence of diabetic retinopathy. This condition is caused by high blood-sugar levels that damage the delicate blood vessels in the retina and, of not treated early, can lead to severe vision loss. Diabetic retinopathy can be managed by keeping blood sugar levels under control.

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