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Tests and diagnosis
By Mayo Clinic staffYour eye doctor may use these tools in examining your eyes:
- Keratometer. This instrument quantifies the amount and orientation of corneal astigmatism by measuring reflected light from the surface of your cornea.
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Keratoscope and videokeratoscope. These devices are used to detect and quantify corneal surface curvature and the presence of astigmatism. A keratoscope uses light to project rings on your cornea. 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.
A keratoscope fitted with a video camera is called a videokeratoscope. A videokeratoscope is the most common instrument used to measure the change in corneal surface curvature, in a process called corneal topography.
- Astigmatism. American Optometric Association. http://www.aoa.org/x4698.xml. Accessed Oct. 27, 2008.
- Preferred practice pattern: Comprehensive adult medical eye evaluation. San Francisco, Calif.: American Academy of Ophthalmology. http://one.aao.org/asset.axd?id=6749e4a0-6a09-4795-8f8d-aec60dc937c9. Accessed Oct. 27, 2008.
- Abad JC, Azar DT. Current concepts, classification and history of refractive surgery. In: Yanoff M, et al. Ophthalmology. 2nd ed. St. Louis, Mo.: Mosby; 2004. http://www.mdconsult.com/das/book/body/108512830-3/764482214/1197/19.html#4-u1.0-B0-323-01634-0..50019-5--cesec5_324. Accessed Oct. 27, 2008.
- Preferred practice pattern: Refractive errors and refractive surgery. San Francisco, Calif.: American Academy of Ophthalmology. http://one.aao.org/asset.axd?id=b5e06307-8a97-4675-8174-367ed4eb355b. Accessed Oct. 27, 2008.
