“Strange” Eye Conditions: Astigmatism

It’s got nothing to do with The Stig hypnotizing you…Top Gear fans will get that.


Source CNIB, Canadian Opthalmological Society

In normal, undistorted vision, the cornea (the clear window in front of the eye) is smooth and equally curved in all directions. With astigmatism, the cornea is “warped”, meaning it curves more in one direction than the other distorting or blurring vision for objects at any distance.

Large amounts of astigmatism are usually inherited, present at birth and frequently remain unchanged throughout life. Small amounts of astigmatism can be acquired any time in life and are, in fact, very common. It often does not require correction.


Correction is not difficult if the distortion proceeds across the cornea in a regular direction. Prescription glasses can often be ordered that neutralize or off set the distortion to the cornea.

If, however, the distortion is irregular, only reshaping the cornea will correct the problem. This is usually done through the use of hard lenses or by replacing it with donated human corneal tissue. While hard lenses are usually better than soft lenses for this correction, some special soft lenses may be helpful to correct mild astigmatism. Large amounts of astigmatism are not easily corrected with lenses as it may wobble on the uneven surface of the cornea. In such instances, a special device called a toric lens may be ground with a curve on the back surface which stabilizes the lens on the cornea.

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