Astigmatism means that a corneal or lens surface is oval like a rugby ball instead of spherical like a basketball. Most astigmatic surfaces have two curves - a steeper curve and a flatter curve. This causes light to focus on more than one point in the eye, resulting in blurred vision at distance or near. Astigmatism often occurs along with nearsightedness or farsightedness.
Blurred vision (near and distance)
Astigmatism can be detected and measured with corneal topography, keratometry, vision testing and refraction.
Astigmatism can be corrected with glasses, contact lenses, or surgically. The most common surgeries used to correct corneal astigmatism are astigmatic keratotomy (procedures that involve placing a microscopic incision on the cornea) and LASIK. The objective of these procedures is to reshape the cornea so it becomes more spherical or uniformly curved.
Illustrations by Mark Erickson
With acknowledgement to St. Lukes Eye Hospital.