Is Astigmatism Causing Your Blurry Vision?
Author: Evan Langsted
If you have been diagnosed with nearsightedness or farsightedness, you may experience some blurry vision, especially when you are not wearing your glasses or contact lenses. But did you know you may also have a common condition known as astigmatism? Astigmatism can also cause blurred vision, as well as headaches and eye discomfort.
What is Astigmatism?
Astigmatism occurs due to an irregular corneal shape or an irregular curvature of the lens inside the eye. Either of these conditions may prevent light from focusing correctly on the retina, and blurred vision at any distance may result, since both the cornea and lens are responsible for focusing the light which enters the eye.
Astigmatism, nearsightedness and farsightedness are known medically as refractive errors, because each of these conditions affects how the eyes "refract" or bend light.
An astigmatic eye does not have the evenly spherical shape which gives clear vision. Instead it has an oval shape or an irregularity of shape caused by a scar on the cornea or some defect in the lens. An oval shape has two curvatures:
- A steeper curvature on its short side; and
- A flatter curvature on its long side
A scar or other irregularity also has several curvatures. Each curvature bends incoming light differently, giving multiple images on the retina or in front of it. Blurry vision is the result.
Your comprehensive visual examination with a qualified ophthalmologist measures how the eyes focus light. This helps your eye doctor to determine the prescription that will help to correct your blurry vision. Some of the sophisticated diagnostics used at Bellevue Lasik and Cornea in Seattle, Washington include:
- Visual acuity -- This is done through a phoropter, where the chin and forehead rest against the designated surfaces and you look through an aperture at the Snellen chart. The eye doctor or his assistant flips between different lenses, asking you to read the smallest line of letters you can see. This test measures your eyes' refractive error and yields a corrective prescription for glasses or contacts.
- Keratometry -- A keratometer measures corneal curvature. A circle of light is focused on the cornea and its reflection is measured. This is a critical measurement in determining proper fit for contact lenses.
- Corneal topography, a more sophisticated procedure, may be used to gain greater details about the shape of the cornea.
The measurements from these tests and others help your eye doctor determine if you have astigmatism, to what degree, and which treatment option will work best to help you achieve your best vision.
Diagnosing and Treating Astigmatism
Medical doctors do not know why astigmatism occurs. In some case it appears to be hereditary. In many cases it is present at birth but symptoms may not be obvious until early adulthood. Astigmatism can improve or worsen over time.
To determine if astigmatism is contributing to your blurry vision, a visit to an experienced ophthalmologist is needed for a comprehensive eye examination. If astigmatism is diagnosed, treatment may be:
- Glasses or contact lenses to alter the way your eyes refract light.
- Laser vision correction, such as LASIK or any of its variants. LASIK alters the cornea's shape by removing a tiny amount of corneal tissue. A highly precise laser beam vaporizes the tissue according to your detailed treatment plan.
- Orthokeratology (Ortho-K) which is a painless, non-invasive procedure that modifies corneal shape through specially-designed rigid contact lenses.