What Is Astigmatism?
Astigmatism is a refractive error caused by an irregular curvature of the cornea (the clear front surface of the eye) or the lens inside the eye. Instead of being perfectly round like a basketball, the cornea is shaped more like a football — causing light to focus on multiple points rather than a single sharp point on the retina.
How Common Is It?
Astigmatism is extremely common — studies suggest it affects between 30% and 40% of the population to some degree. Mild astigmatism may not require correction, while moderate to severe astigmatism causes noticeable vision problems.
Symptoms of Astigmatism
- Blurry or distorted vision at all distances (not just near or far)
- Difficulty seeing fine details, especially at night
- Eye strain and fatigue, particularly after reading or screen use
- Headaches
- Squinting
- Halos or streaks around lights at night
What Causes Astigmatism?
Most astigmatism is corneal astigmatism — caused by an irregularly shaped cornea. It is usually present from birth and tends to be hereditary. Lenticular astigmatism occurs when the lens inside the eye has an irregular shape. Astigmatism can also develop after eye injury, surgery, or as a result of keratoconus (a progressive thinning of the cornea).
How Is Astigmatism Diagnosed?
An optometrist diagnoses astigmatism using a keratometer (to measure corneal curvature) and a refraction test. A preliminary screening can be done with an astigmatism fan chart — the radial line test used in VisionCheck — where certain lines appear darker or blurrier than others if astigmatism is present.
Treatment Options
Glasses
The simplest correction. Glasses for astigmatism have a cylindrical lens component (indicated by the "CYL" and "AXIS" values on your prescription) that compensates for the irregular corneal shape.
Toric Contact Lenses
Specially designed contacts that have different powers in different meridians of the lens, and are weighted to stay properly oriented on the eye.
Orthokeratology (Ortho-K)
Rigid gas-permeable contact lenses worn overnight to temporarily reshape the cornea. Vision is corrected during the day without lenses.
LASIK and PRK Surgery
Laser eye surgery permanently reshapes the cornea to correct astigmatism. LASIK is the most common procedure; PRK is preferred for patients with thin corneas.
Test Yourself for Astigmatism
VisionCheck includes a free astigmatism fan chart test as part of its online vision screening. If certain lines in the radial pattern appear darker, blurrier, or more distinct than others, astigmatism may be present. Take the test and get your results in minutes.
Sabroe Enterprise
VisionCheck Eye Health Team