What is the difference between keratoconus and “common” astigmatism?
Astigmatism is a common condition where the curvature of one or more of the optical surfaces of the eye (the cornea and lens surfaces) are more “curved” in one direction than the other. In “regular” astigmatism the maximum and minmum powers of the cornea are aligned at 90 degrees to each other, while in “irregular astigmatism” they do not align. An egg is a good example of a surface with regular astigmatism, whereas an orange (sphere) is a good example of a surface which has no astigmatism. Keratoconus is a degenerative condition where the cornea thins in affected areas. This can lead to astigmatism – often regular at first but becoming increasingly irregular as the condition progresses. It is possible to correct regular astigmatism with glasses or soft contact lenses, however for irregular astigmatism, where the cornea can often have multiple curves (giving multiple focuses), it is impossible to correct these multiple focuses with spectacles or soft contact lenses.
Astigmatism is a common condition where the curvature of one or more of the optical surfaces of the eye (the cornea and lens surfaces) are more “round” in one direction than the other. In “regular” astigmatism the maximum and minimum powers are aligned at 90 degrees to each other while in “irregular” astigmatism they do not align. An egg is a good example of a surface with “regular astigmatism”. Keratoconus is a degenerative condition where the cornea thins in affected areas. This can lead to astigmatism – often regular at first but becoming increasingly irregular as keratoconus progresses.
