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What is Astigmatism?
Astigmatism is a common and treatable eye problem that causes blurry or distorted vision. In the United States, one in every three people has astigmatism.
Astigmatism is a refractive error, which means the shape of the eye doesn't bend or refract light rays correctly. 153 million people around the world have a refractive error. Other common refractive eye errors include nearsightedness (myopia) and farsightedness (hyperopia).
The two types of astigmatism are corneal and lenticular. Astigmatism occurs when the cornea or lens curvature is abnormal, which causes blurred vision at all distances.
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With corneal astigmatism, the cornea has more of an oval shape instead of a round shape. With lenticular astigmatism, the lens is misshapen. In a normal eye, each of these elements should be perfectly round.
An irregular cornea or lens prevents the eye from focusing light correctly on the retina. The area in the eye converts light into signals sent to the brain for visual recognition.
Astigmatism occurs naturally or is caused by an eye injury, eye disease, or eye surgery.
Many treatment options are available to help individuals with astigmatism to see better. Common treatments for astigmatism include corrective lenses and surgery.
Symptoms of Astigmatism
The most common symptoms of astigmatism are:
- Blurry vision
- Needing to squint to see clearly
- Difficulty seeing at night
Individuals with mild astigmatism might not notice any symptoms. That’s why it’s essential to get regular eye exams. An optometrist or ophthalmologist can diagnose astigmatism even if it’s undetected by the patient. Frequent eye exams are vital for children, who may not tell if their vision is normal, which is why all children should visit a pediatric optometrist at least once annually.
How is Astigmatism Diagnosed?
The optometrist can diagnose astigmatism during a comprehensive eye exam.
A comprehensive eye exam includes:
- A visual acuity test to check the ability to discern shapes and details.
- A refraction to determine your refractive error (including astigmatism). The eye doctor bases your eyeglass prescription on the results of this test.
- A visual field test to check the peripheral (side) vision.
- An eye muscle function test to check for issues with the muscles around the eyeballs.
- A pupil response test to check how your pupils respond to light and viewing objects at near.
- A tonometry test to measure eye pressure.
- Dilation to check for problems with the inner parts of the eyes.
How Do Lights Look With Astigmatism?
Astigmatism may distort the appearance of lights. This condition can cause several visual distortions, including blurriness, a glare, streaking, starburst, or a halo effect around lights, making driving at night difficult. However, glares or a halo appearance around lights do not necessarily indicate astigmatism, as this phenomenon is also caused by other vision conditions like nearsightedness (myopia) or cataracts.
How Does Astigmatism Affect Night Driving & Vision?
Astigmatism can impair vision at night and make driving difficult. Individuals with astigmatism may notice other symptoms when driving at night, including:
- Blurring or fuzziness around lights and other objects
- Halos around lights
- Lights appearing ‘streaky’
- Increased glare from lights
- Increased squinting to see more clearly
Because astigmatism can distort the appearance of things like streetlights and car headlights, it can be hazardous to drive at night with untreated astigmatism. Individuals who start having trouble with their night vision or notice any of these symptoms should immediately schedule an exam with their eye doctor.
Treatment for Astigmatism Lights at Night
Many treatment options are available to help restore clear vision to individuals with astigmatism. The most common treatments for astigmatism include:
- Eyeglasses help correct the way light bends into the eye and correct other vision issues, like nearsightedness or farsightedness.
- Contact lenses correct the way that light bends into the eye and other vision issues. There are many different contact lenses, including soft disposable lenses, hard gas permeable, extended-wear, or bifocal contact lenses.
- Orthokeratology in which the patient wears rigid contact lenses while sleeping to correct the shape of the cornea.
- A toric lens implant is a surgical procedure that involves replacing the eye’s misshapen lens with a lens implant that corrects the astigmatism.
- LASIK surgery is a type of eye surgery in which a special laser is used to reshape the cornea and change its focusing power.
- PRK (photorefractive keratectomy) is a similar type of laser surgery that uses a laser to reshape the cornea.
Patients who already wear glasses or contact lenses that correct their astigmatism should wear them when driving at night. Patients who are still having trouble seeing objects and lights clearly at night should have their prescription adjusted or consult their eye doctor to see if there are other underlying causes.