A: It is a measurement of sight. "20/20" vision refers to 8.7mm tall letter that a person with "average" or "normal" vision can see at 20 feet. Someone with 20/40 vision can only be 20 feet away from an object to see what a person with normal vision can see at 40 feet. Similarly, the person with 20/400 vision can only be 20 feet away from an object to see what a person with 20/20 vision can see at 400 feet. Most states require 20/40 or better in at least one eye to get a driver's license without glasses or contact lens restriction. Note that the term “20/20” does not reveal the quality of vision.

A: This refers to the best vision that your eyes are capable of seeing with the best corrective glasses and / or contact lenses. It is generally a reflection of the health of the eyes such as with nearsightedness, farsightedness, or astigmatism. Best corrected vision is measured on the same eye chart as the visual acuity without correction.

A: Yes. Diabetes can cause severe problems with your sight. It is very important that your eyes are checked every year, preferably with drops to dilate the pupil, so that the retina (back of the eye) can be examined thoroughly.

A: Parents should have their children’s eyes checked at three important stages during their early development: (1) when the infant is about 6 month old. A pediatric ophthalmologist makes sure that the eyes are working well together and there are no rarely occurring but significant defects, such as cataracts and tumors that could threaten the child’s vision; (2) between the ages of 2 and 3, before child enters preschool. A pediatric / general ophthalmologist at this time checks for any signs of developmental disorders, including lazy eye, crossed eyes (strabismus), nearsightedness, farsightedness, and astigmatism. If a problem is found, effective therapy can usually begin immediately; (3) between the ages of 5 and 6, before the child enters kindergarten. Eye doctor now tests for sharpness of vision and corrects deficiencies by prescribing eye glasses. A child’s eyes finish developing by the age of 8-9 years.

Early detection of eye problems can sometimes prevent significant damage to the eye or to vision. If any member of your family has eye problems, then it is important to have your child’s eyes tested at an early age.

A: Night blindness is more appropriately called as “impaired dark adaptation.” People with night blindness see poorly in the darkness but see normally when adequate amounts of light are present. The condition does not actually involve true blindness, even at night.

A: Color blindness, more accurately called color deficiency, is a term used for a deficiency in recognizing certain colors. Most color perception defects are for red or green or both. Another form of color blindness; yellow-blue is the second most common form, but it is rare and could be a result of some optic nerve disease. Complete color deficiency, where all colors are seen as varying shades of black and white is almost unknown. About 10% of males have a color perception defect, but this is rare in females.

A: Color deficiency is a sex linked character. Females are either not affected or they are the carriers with a normal vision. The males within the same family are affected. There is only a 50/50 chance that sons of carrier mothers will have altered color vision.

A: It depends upon the kind of job you do. Certain jobs, such as printing inks, textiles, and paints etc. require a precise perception of color. Because of your limited ability to recognize colors accurately, your performance at these jobs may be affected.

A: Generally, color deficient people are not denied a driving license. However, remember that a person with color blindness may drive through a red traffic light and cause a fatal accident. Driving laws in certain places are more strict and may limit color blind people from driving heavy commercial machinery.