Astigmatism – Just an Eye Shape Problem

Astigmatism most commonly caused by the cornea being a cylinder rather than being like a soccer ball this produces two focus lines separated and 90 degrees to each other.

An optical system with astigmatism is one where rays that propagate in two perpendicular planes have different foci; see Video above.

Astigmatism is quite common. Studies have shown that about one in three people suffers from it. The prevalence of astigmatism increases with age. Although a person may not notice mild astigmatism, higher amounts of astigmatism may cause blurry vision, squinting, asthenopia, fatigue, or headaches.

There are a number of tests that are used by optometrists and ophthalmologists during eye examinations to determine the presence of astigmatism and to quantify the amount and axis of the astigmatism. A keratometer may be used to measure the curvature of the steepest and flattest meridians in the cornea’s front surface. Corneal topography may also be used to obtain a more accurate representation of the cornea’s shape. An auto refractor or retinoscopy may provide an objective estimate of the eye’s refractive error and the use of Jackson cross cylinders in a phoropter or loose lenses in a trial frame, may be used to subjectively refine those measurements. An alternative technique with the phoropter requires the use of a “clock dial” or “sunburst” chart to determine the astigmatic axis and power.

Astigmatism may be corrected with eyeglasses, contact lenses, or refractive surgery.http://en.wikipedia.or

More Information on Astigmatism