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Understanding Astigmatism: Information, Symptoms, and Treatment
The Basics | Symptoms | Treatment
Treatment
How Do I Know If I Have Astigmatism?
People usually complain of blurred vision or children may fail their vision exam at school.
The doctor may use one or more of these four tests to detect astigmatism and measure your level of astigmatism.
Vision test. It's the simplest yet most important part of an eye exam. Using a standardized chart, patients read the letters they can see from 20 feet away. If your vision is 20/20, this means you can see at 20 feet what a normal eye can see from 20 feet. If your vision is 20/80, this means you can only see at 20 feet what a normal eye should be able to see from 80 feet away.
Refraction. The doctor uses loose lenses or a lens machine (phoropter) to hold corrective lenses in front of your eye. The doctor looks inside a handheld device called a retinoscope to determine if any refractive error is present. Then the eye doctor will offer you different choices in lenses through the phoropter to refine the correction until you can see the vision chart clearly. After both eyes are measured your doctor will write a prescription for eyeglasses based on which corrective lenses worked for you.
Keratometry. This machine measures the curvature of your central cornea. Corneas that have no astigmatism exhibit uniform, round curvature. Corneas with astigmatism have an inconsistent curvature. The keratometer determines the steepest and the flattest curves. These measurements tell your doctor about your corneas' shape and focusing power. The keratometer is also used to fit contact lenses and to monitor corneal curvature after eye surgery.
Corneal Topography. This advanced technology provides the most detailed information about the shape of a cornea. The patient looks at a visual target while the device collects thousands of tiny measurements. A computer then constructs a color map on the computer from the data. This corneal map allows the doctor to see a three-dimensional picture of your cornea. Such sophisticated measurements are important for planning refractive surgery and occasionally for fitting contact lenses.
The Basics | Symptoms | Treatment
