We all make errors. Some we can control, others simply are part of our biology. Such is the case with ‘refractive errors,’ a collection of common eye distortions that affect vision.
More specifically, “a refractive error is an optical condition in which rays of light do not focus perfectly on the retina, often resulting in blurred or imperfect vision,” explains Dr. Sharon Jick, an ophthalmologist with Complete Eye Care. People who have refractive errors are born with or develop a misshapen cornea, the transparent front surface of the eye. A normal cornea is spherical, but astigmatism is marked by an elliptical or football-shaped cornea, which affects how light is refracted as it passes through.
“In the case of astigmatism, light rays don’t focus on the retina at a single point. In fact, ‘astigmatism’ is derived from a Greek word that literally means, ‘without a point.’ Instead, there are two separate areas of focus,” Jick says.
Astigmatism affects both children and adults, and the condition can change over time. “With astigmatism, patients will have blurred vision as their main symptom at both distance and near,” says Dr. Andrew Blatt, an ophthalmologist with St. Louis Eye Care Specialists. Other symptoms include eyestrain and headaches, especially after reading for a prolonged period. “Patients will often squint in order to see better when the astigmatism is uncorrected,” he adds.
In most cases, it is impossible to determine the cause of astigmatism without doubt, and many people are born with it. However, the condition may develop due to a variety of circumstances. “Astigmatism can be acquired by the cornea shape being changed by an eyelid lesion pressing on it, or if the cornea has sustained trauma or an infection,” Blatt says. “If patients have seasonal allergies and rub their eyes significantly, it can result in an increased amount of corneal astigmatism. It can also be acquired in patients with diabetes whose lens may change shape because their blood sugars are elevated.”
As with other refractive errors, vision problems caused by astigmatism are usually easy to correct with glasses or contact lenses. “However, refractive surgery is an exciting option for patients who prefer to be less dependent on glasses or contacts,” Jick adds. LASIK and PRK surgical techniques allow surgeons to sculpt the cornea, reshaping it and correcting astigmatism and other refractive errors.
“For patients with cataracts and significant astigmatism, there are toric lens implants that will correct the astigmatism quite well,” Blatt says. “Because of the many treatment options these days, patients with astigmatism can look forward to having excellent corrected vision.”