What is astigmatism?
Astigmatism is a common vision problem caused by an error in the shape of the cornea. With astigmatism, the lens of the eye or the cornea, which is the front surface of the eye, has an irregular curve. This can change the way light passes, or refracts, to your retina. This causes blurry, fuzzy, or distorted vision. Farsightedness and nearsightedness are two other types of problems with the way light passes to your retina. Farsightedness is called hyperopia. Nearsightedness is called myopia.
The two main types of astigmatism are corneal and lenticular. A corneal astigmatism happens when your cornea is misshapen. A lenticular astigmatism happens when your lens is misshapen.
It’s not known what causes astigmatism, but genetics is a big factor. It’s often present at birth, but it may develop later in life. It may also occur as a result of an injury to the eye or after eye surgery. Astigmatism often occurs with nearsightedness or farsightedness.
Astigmatism can occur in children and adults. Your risk of developing astigmatism may be higher if you have any of the following:
- a family history of astigmatism or other eye disorders, such as keratoconus (degeneration of the cornea)
- scarring or thinning of your cornea
- excessive nearsightedness, which creates blurry vision at a distance
- excessive farsightedness, which creates blurry close-up vision
- a history of certain types of eye surgery, such as cataract surgery (surgical removal of a clouded lens)
The symptoms of astigmatism may differ in each person. Some people don’t have any symptoms at all. The symptoms of astigmatism include:
- blurry, distorted, or fuzzy vision at all distances (up close and far away)
- difficulty seeing at night
- eye irritation
See a doctor if you have symptoms of astigmatism. Some symptoms may also be due to other health or vision problems.
An optometrist or ophthalmologist diagnoses astigmatism through a comprehensive eye examination. An optometrist is a doctor who diagnoses vision problems and eye diseases. An ophthalmologist is a doctor who provides medical and surgical treatment of vision problems and eye diseases. There are several tests optometrists and ophthalmologists may use during your eye examination to diagnose astigmatism.
Visual acuity assessment test
During a visual acuity assessment test, your doctor will ask you to read letters from a chart at a specific distance to determine how well you can see the letters.
A refraction test uses a machine called an optical refractor. The machine has multiple corrective glass lenses of different strengths. Your doctor will ask you to read a chart while looking through lenses that are different strengths on the optical refractor. They’ll eventually find a lens that appropriately corrects your vision.
Keratometry is a way for your doctor to measure the curvature of your cornea. They will do this by looking at your eye through a keratometer.
Mild cases of astigmatism may not require treatment. Your doctor may treat astigmatism that causes vision problems by using one of the following methods.
Orthokeratology (Ortho-K) is a treatment that uses rigid contact lenses to temporarily correct the irregular curvature of your cornea. You’ll wear rigid contact lenses for limited periods of time. You may wear them during sleep and then remove them during the day. Some people have clear vision during the day without corrective lenses when undergoing Ortho-K. The benefits of Ortho-K are only present when using it. Your vision will return to its previous state after stopping Ortho-K.
Your doctor may recommend refractive surgery if you have a severe case. This type of surgery involves using lasers or small knives to reshape your cornea. This will permanently correct your astigmatism. The three common surgeries for astigmatism are laser in situ keratomileusis (LASIK), photorefractive keratectomy (PRK), and radial keratotomy (RK). All surgeries carry some risks. Talk to your doctor about the risks and benefits before getting surgery for astigmatism.
A lazy eye can occur if astigmatism in one eye isn’t corrected. Lazy eye is also called amblyopia.
Corrective lenses or surgery can usually restore your vision to normal. There’s no known way to prevent astigmatism from developing.