What is astigmatism and how is it detected?
Astigmatism is a common refractive error caused by an irregular curvature of the cornea or lens, which blurs vision at all distances. During a comprehensive eye exam, your optometrist uses a keratometer or autorefractor to measure the shape and steepness of your cornea. A refraction test, where you look through a phoropter and compare lens options, confirms the exact degree and axis of astigmatism. This is not a disease but a variation in how your eye focuses light.
The prescription process for astigmatism
Optometrists address astigmatism by recording two key numbers on your prescription: cylinder (CYL) and axis. Cylinder measures the lens power needed to correct the irregular curve, while axis (measured in degrees from 0 to 180) indicates the orientation of that curve. A standard spherical lens corrects nearsightedness or farsightedness alone; for astigmatism, a toric lens is used, which has different powers in different meridians. Your optometrist will fine-tune these values during the refraction to achieve crisp, comfortable vision.
Glasses and contact lenses for astigmatism
Glasses with toric lenses are the most straightforward solution, and they correct most cases of astigmatism. For contact lenses, your optometrist will assess whether you are a good candidate for toric soft lenses or rigid gas permeable (RGP) lenses, which can offer sharper vision for higher astigmatism. The fitting process for toric contacts is more precise than for spherical lenses, as they must stay aligned on the eye. A follow-up evaluation ensures the lens rotates correctly and provides stable vision.
Special considerations and other treatments
- Irregular astigmatism from eye injury or conditions like keratoconus may require custom or specialty lenses, such as scleral lenses.
- Laser vision correction (LASIK or PRK) can reshape the cornea to reduce astigmatism, but candidacy depends on your overall eye health, age, and stability.
- Your optometrist will also check for dry eye or digital eye strain, as these can affect how well you tolerate correction for astigmatism.
When to see an optometrist for astigmatism
If you experience persistent blurriness, headaches, eye strain, or difficulty seeing at night, schedule an eye exam. Only a comprehensive exam by a licensed optometrist can accurately measure astigmatism and rule out other conditions. Remember, routine exams also support overall wellness by detecting early signs of diabetes or high blood pressure through the eyes.
Your optometrist is your partner in clear, comfortable vision. If you have any questions about your prescription or lens options, bring them to your next visit.