Astigmatism

What is Astigmatism?

Astigmatism is one of the most common refractive errors, affecting an estimated 30–40% of adults to some degree. It occurs when the cornea or lens is not perfectly spherical — instead of being round like a football, it is shaped more like a rugby ball. This causes light to focus at two different points rather than one, producing blurred or distorted vision at all distances. Most cases of astigmatism are mild and easily corrected.

Symptoms

• Blurred or distorted vision at all distances
• Eye strain and headaches, particularly after prolonged reading or screen use
• Squinting in an attempt to see more clearly
• Difficulty with night vision — halos around lights
• Asthenopia (eye fatigue)

Causes

• Irregular curvature of the cornea (corneal astigmatism) — the most common type
• Irregular curvature of the crystalline lens (lenticular astigmatism)
• Corneal scarring following injury or infection
• Keratoconus — a progressive thinning of the cornea

Diagnosis

Refraction assessment during a standard eye examination. Corneal topography may be used to map the exact shape of the corneal surface in more complex cases.

Treatment

Mild astigmatism may need no treatment. Spectacles or toric contact lenses correct the irregular focus. Toric intraocular lenses (IOLs) at the time of cataract surgery can address pre-existing astigmatism. Laser vision correction (LASIK, LASEK) reshapes the cornea.