Astigmatism is one of the most common refractive errors, alongside nearsightedness (myopia) and farsightedness (hyperopia). It happens when the cornea, or the lens inside the eye, has an irregular curve rather than a perfectly round one. Light entering the eye then focuses on two or more points instead of a single point on the retina, which blurs or stretches vision at any distance, near or far.
Most people have at least a small, harmless degree of astigmatism, often present from birth. It usually only needs correction once it starts affecting everyday vision: reading, driving, or long stretches at a screen.
What causes astigmatism
The exact cause isn’t always clear, but astigmatism tends to run in families and is usually present from an early age. It can also develop or change after an eye injury, eye surgery, or a condition called keratoconus, where the cornea gradually thins and bulges into a cone shape. Regular eye exams are the best way to catch a meaningful change in curvature early.
Common symptoms
- Blurred or distorted vision at any distance
- Eye strain or discomfort, especially after reading or screen use
- Frequent headaches
- Squinting to bring objects into focus
- Difficulty with night vision, or halos and streaks around lights
Types of astigmatism
Astigmatism is usually described by where it occurs and how regular the curve is.
- Corneal astigmatism: an irregular curve in the cornea, the clear front surface of the eye. This is the more common form.
- Lenticular astigmatism: an irregular curve in the eye’s internal lens rather than the cornea.
- Regular astigmatism: the steepest and flattest curves sit at a consistent angle, roughly 90 degrees apart, and correct predictably with glasses or contact lenses.
- Irregular astigmatism: the curve varies unevenly across the eye, often after an injury or with keratoconus, and can need more specialized correction.
How it’s diagnosed
A comprehensive eye exam is the only reliable way to confirm astigmatism and measure it accurately. An optometrist will typically check visual acuity, then measure the curvature of the cornea with a keratometer or, for a more detailed map, corneal topography. These readings give the exact cylinder power and axis needed to write an accurate prescription.
Correcting astigmatism
Astigmatism is very manageable once it’s measured correctly. Common options include:
- Prescription eyeglasses with a cylinder power ground into the lens to compensate for the irregular curve.
- Toric contact lenses, designed specifically for astigmatism so they hold a stable orientation on the eye rather than rotating.
- Refractive surgery, such as LASIK or PRK, which reshapes the cornea for suitable candidates.
Because the correction depends on precise axis and power measurements, an up-to-date eye exam matters more than the astigmatism itself. Vision Express offers comprehensive eye exams and can fit both glasses and toric contact lenses to a current, accurate prescription.
When to see a doctor
Book an exam sooner rather than later if vision changes suddenly, distortion gets noticeably worse, or one eye seems to fluctuate on its own. These can be signs of keratoconus or another corneal change that benefits from early monitoring, not just a stronger prescription.