The intricate process of vision, which has so many complex parts and interactions, can sometimes go wrong. The four most common vision problems - nearsightedness, farsightedness, astigmatism and presbyopia - are usually caused by focusing problems of the cornea or the lens or by an abnormal shape of the eye. Most problems with focusing can be corrected with eyeglasses, contact lenses or surgery that adjusts the curvature of your cornea.
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| Nearsighted Vision Correction |
You see an object clearly when it is properly focused. That means your cornea and lens have adjusted the point of focus so that an image falls sharply defined onto your retina. If the focusing powers of your cornea and lens aren't coordinated with the length or the shape of your eye, however, the image you see is blurred.
Nearsightedness
If you're nearsighted - a condition called myopia (mi-O-pe-uh) - you can see objects that are near to you clearly, but objects farther away are blurry. You're nearsighted if your eyeball is elongated from front to back rather than round. This causes the object you're looking at to be sharply focused in front of the retina instead of on the retina. Even with a round eye you can be nearsighted if your cornea or lens is too steeply curved.
Nearsightedness is a common problem, affecting nearly 3 out of 10 people. Many people first notice the condition during childhood when, for example, they have trouble making out what the teacher writes on the board at school. It affects boys and girls equally and tends to run in families. The problem can progress quickly during these early years, sometimes requiring new corrective lenses more than once a year. Vision tends to stabilize during the young adult years, so during your 20s and 30s you may not need a change in your lenses.
Concave lenses, which are thinner in the middle than at the edges, can correct myopia. You can wear the lenses as glasses or contacts. Another way of correcting this problem - refractive surgery - is growing in popularity. It's a brief procedure that reduces the curvature of your cornea so that the light entering your eye focuses directly on your retina again. Two types of refractive surgery are photorefractive keratectomy and LASIK surgery.
Colorblindness
Most people who have what's called colorblindness aren't really colorblind. That would mean they see only black and white, Actually, their problem is that it's hard to tell the difference between certain shades of color. Most people with colorblindness can't tell the difference between red and green. Others can't tell the difference between shades of blue and yellow.
The problem is usually inherited, though eye diseases and some medicines also can cause it. About 8 percent of men and 1 percent of women are born having trouble with their color discrimination. Some people are simply unaware of their color vision problems.
The problem arises from color pigment deficiencies in the cone cells in your retina. These pigments allow you to distinguish between many hues of colors that are based on the three primary colors: red, blue and green. If you're missing one or more color pigments, you may see only two of the primary colors. Confusing the red light and the green light of a traffic signal is a well-known problem associated with colorblindness. People with colorblindness may also be unable to distinguish ripening fruit and vegetables in a garden, for example, a tomato changing color from green to red.
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| Nearsighted Vision Correction |
Doctors can diagnose color vision deficiencies and determine their severity. There's no cure for the inherited forms of colorblindness. However, if a disease causes poor color vision, treatment may slow or reverse the deficiency. Doctors can also suggest ways you can compensate for the problem. Specially tinted eyeglasses may help you distinguish between confusing colors.
And you can learn to recognize colors by their brightness and location, such as the positions of the red light and the green light on a traffic signal. To find out more, you can check out Nearsighted Vision Correction.