What is astigmatism? Astigmatism is a flaw in the curvature of your eye’s cornea or lens causing issues with proper vision and may require correction.
Imagine the shape of an eyeball equivalent to a basketball. If an eye is perfectly spherical, there is no astigmatism. The light evenly bends when it comes into the eye, providing a clear view. However, imagine the eye is shaped similar to an American football. The light bends in multiple directions, causing blurred vision. This is astigmatism.
There are two types of astigmatism: corneal and lenticular. Both types are caused by a misshape of either the cornea or the lens.
About 1 in 3 people have astigmatism. Usually, a small amount of astigmatism can be found in normal eyes and detected in young children. The degree of astigmatism can increase as a child grows. It’s common for people with astigmatism to also have refractive errors in their eyesight, like nearsightedness or farsightedness. All three conditions affect how your eyes refract (bend) light and are thus called refractive errors.
Even though astigmatism is prevalent, doctors don’t know why cornea or lens shape differs among individuals. What they do know is that the likelihood of developing astigmatism is usually inherited. One can also develop it after an eye injury, eye disease, or surgery. A very rare condition called keratoconus may trigger astigmatism by creating a cone-like bulging of the cornea. If this is the case, one will need contact lenses to be able to see clearly. One study has shown that infants born preterm have astigmatism at a higher percentage than those born closer to their due date. Children must be tested early to slow the progression of astigmatism and preserve their sight.
Myth: One cannot develop or worsen astigmatism from reading in low light or sitting very close to the television. However, doing so frequently can cause eye strain.
Symptoms that can indicate astigmatism are:
Blurred or distorted vision
People with astigmatism may experience mild to severely distorted vision due to the refraction of light, depending on the degree of astigmatism. While nearsightedness (myopia) makes far-away objects blurry and farsightedness (hyperopia) makes close-up objects blurry, things are blurry at every distance with astigmatism.
Eye strain and fatigue
Whether working at a computer or driving a car, one’s eyes are constantly adjusting and trying to focus on a clear image. Over time, having blurred or distorted vision can cause eye strain and eye fatigue.
Frequent headaches or dizziness and squinting
Eye strain can lead to other symptoms, like dizziness and headaches. You may find yourself squinting to see things more clearly, which can cause facial fatigue and headaches.
Difficulty seeing at night
Symptoms of astigmatism may worsen when it’s dark. In low light, pupils dilate to let more light into the eye in order to see. But astigmatism makes blurred vision worse. The eye allows more peripheral light in, which can create a halo effect when looking at lights. Halos and glare from light can make it difficult to focus in the dark and cause dangerous conditions, such as driving at night with uncorrected vision.
Depending on the severity, different treatment plans may be prescribed by one’s eye doctor. If the astigmatism is mild, the doctor may suggest no treatment at all. Corrective lenses are the usual approach.
Corrective lenses bend the incoming light rays in a way that compensates for the error caused by faulty refraction. In this way, images are properly projected onto the retina. These may be in the form of glasses or contact lenses. Lenses for astigmatism will need:
- a spherical power, to correct the near or far-sightedness
- a cylinder power, to correct the astigmatism
- an axis designation, to describe the positioning of the cylinder correction
Traditionally, doctors would prescribe orthokeratology, or corneal refractive therapy for more severe cases. This involves wearing fitted, rigid contact lenses called RGP (rigid gas-permeable) lenses overnight to reshape the cornea. RGP does not permanently improve vision, but its effect lasts for hours after wearing them.
Today, eye patients have more comfortable options with soft contact lenses called toric lenses as long as the degree of astigmatism is not too high. These lenses can bend light more in one direction than the other. Some people may benefit from laser surgery, including LASIK where a laser is used to reshape the cornea.
If you have some of the symptoms listed here, you may have astigmatism. Please visit your ophthalmologist for a complete eye exam for an accurate diagnosis and treatment plan.