Common Vision Problems

The most common vision problems are: Myopia, Astigmatism, hyperopia and presbyopia. These are called "refractive disorders" because they have to do with how the eye bends (refracts) or focuses light. Each of these conditions is related to either the shape of the eye itself, the shape of the cornea or the condition of the lens as it ages.

Myopia
or "nearsightedness" is the condition of not being able to focus at a distance while near objects may be seen clearly even without the aid of glasses. Myopia can vary by degrees from mild to severe. Myopia results from the shape of the eye being too long in proportion to the curve of the cornea, the eye's outer covering. This causes light entering the cornea to fall short of focusing on the retina, the imaging "screen" at the back of the eye. Imagine a film or slide projection where the image is blurred because the light is not properly adjusted to a focal point on the surface of the screen.

Astigmatism
is the term used to describe any blurring of vision caused by a cornea that is oval shaped rather than round. This irregular football shape causes light to enter the eye unevenly from different angles at the same time. Light then focuses at multiple points on, in front of and/or behind the retinal screen. This can result in "double vision" or a difficulty in seeing clearly at either near or far distances. Astigmatism is often found in conjunction with cases of myopia or hyperopia. It is the most common of focal problems.

Hyperopia
is the condition of not being able to focus clearly at close range while distant objects may be viewed easily without the aid of glasses. Hyperopia or "farsightedness" results from the length of the eye being too short in proportion to the curvature of the cornea. Light is not accurately focused on the retinal screen but at a point just beyond it, thus causing a blurring of vision close up. Hyperopia also can vary from mild to more extreme cases.

Presbyopia
or "old eye" is a condition of reduced elasticity of the lens due to the normal aging process. This loss of elasticity affects the ability of the eye to focus close up. The condition may become evident around age 40, making reading of small print more difficult.

 

   
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