Tests and diagnosisBy Mayo Clinic staff
To diagnose astigmatism, your eye doctor may:
- Measure reflected light. By measuring light reflected from the surface of your cornea, a device known as a keratometer quantifies the amount and orientation of corneal astigmatism.
Measure the curvature of your cornea. Using light to project rings on to your cornea, a device called a keratoscope measures the amount of curvature to your cornea's surface and can confirm the presence of astigmatism. Observation through the keratoscope of the reflection of light from your cornea and inspection of the shape and spacing of the rings provide information about the degree of astigmatism.
To measure the change in corneal surface curvature, a process called corneal topography is used. Corneal topography uses a videokeratoscope, which is a keratoscope fitted with a video camera.
- Mian SI. Visual impairment in adults: Refractive disorders and presbyopia. http://www.uptodate.com/home/index.html. Accessed Nov. 22, 2010.
- Astigmatism. American Optometric Association. http://www.aoa.org/x4698.xml. Accessed Nov. 21, 2010.
- Preferred practice pattern: Comprehensive adult medical eye evaluation. San Francisco, Calif.: American Academy of Ophthalmology. http://one.aao.org/ce/practiceguidelines/ppp_content.aspx?cid=64e9df91-dd10-4317-8142-6a87eee7f517. Accessed Nov. 21, 2010.
- Preferred practice pattern: Refractive errors and refractive surgery. San Francisco, Calif.: American Academy of Ophthalmology. http://one.aao.org/ce/practiceguidelines/ppp_content.aspx?cid=e6930284-2c41-48d5-afd2-631dec586286. Accessed Nov. 21, 2010.