Astigmatism

Astigmatism is a refractive correction where light that enters the eye is focused at two points instead of one point inside the eye. The ideal cornea centrally is a slice off of a sphere, where the radius of curvature is the same in the X axis (horizontal axis across the sphere) as it is in the y axis (vertical axis up and down the sphere) across the surface of the sphere. Picture a raquetball, then picture cutting the raquetball in half. You now hold half a sphere. Let this represent the ideal cornea. Hold the raquetball between your thumb and forefinger and gently press the two fingers together. The Y axis (imaginary vertical line straight up and down between your two fingers) will increase in curvature much more than the X axis (imaginary horizontal line across ball, intersecting the Y axis perpendicularly) of the ball surface. The half raquetball will cease to be round and take on an oval shape. In a cornea or other refractive element in the eye of this shape, light focusing will be more powerful in the X axis meridian and focus before the light focusing of the power in the Y axis meridian. This creates two focal points in the eye and the perception of blur to the person with the astigmatism. People with astigmatism may be blurry at distance and near, whereas farsighted people are usually blurry at near and nearsighted people are usually blurry at far. Astigmatism also may cause certain letters or characters appear more blurry than others. Contact lenses ARE available for people with astigmatism. There is considerable time and skill involved in fitting patients with these lenses but it can be done for ALL astigmatisms if the patient is highly motivated to try.

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