astigmatism

Astigmatism is a common refractive error caused by an irregular curvature of the cornea or lens. Light does not focus at a single point on the retina, producing blurred or distorted vision at all distances. It often occurs with myopia or hyperopia and is not a disease in itself.

Most astigmatism is regular, with two principal meridians of curvature, usually near 90 and 180 degrees. Irregular astigmatism results from corneal scarring, keratoconus, or trauma and is more difficult to correct with standard lenses. The amount of astigmatism is described in diopters (D) and the axis indicates orientation.

Symptoms include blurry vision, eye strain, headaches, squinting, and difficulty with night driving. Diagnosis involves a comprehensive eye examination, with refraction testing, keratometry to measure corneal curvature, and often corneal topography. A retina exam may be performed to rule out other conditions.

Treatment depends on severity and needs. Mild astigmatism may not require correction. Corrective options include eyeglasses with cylindrical (toric) lenses, toric contact lenses, or refractive surgery such as LASIK or PRK for eligible individuals. Irregular astigmatism may require specialty lenses or other procedures.

Astigmatism is common and often present from birth; it can change over time, especially in children or after eye surgery or injury. Regular eye exams help monitor changes and adjust treatment as needed.