Corneal topography, also known as photokeratoscopy or videokeratography, is a non-invasive medical imaging technique for mapping the surface curvature of the cornea, the outer structure of the eye. Since the cornea is normally responsible for some 70% of the eye’s refractive power, its topography is of critical importance in determining the quality of vision.
The three-dimensional map is therefore a valuable aid to the examining ophthalmologist or optometrist and can assist in the diagnosis and treatment of a number of conditions; in planning refractive surgery such as LASIK and evaluation of its results; or in assessing the fit of contact lenses. A development of keratoscopy, corneal topography extends the measurement range from the four points a few millimeters apart that is offered by keratometry to a grid of thousands of points covering the entire cornea. The procedure is carried out in seconds and is completely painless.
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Visual Field Testing
A visual field test measures the range of your peripheral or “side” vision to assess whether you have any blind spots (scotomas), peripheral vision loss or visual field abnormalities. It is a straightforward and painless test that does not involve eye drops but does involve the patient’s ability to understand and follow instructions.
An initial visual field screening can be carried out by the optometrist by asking you to keep your gaze fixed on a central object, covering one eye and having you describe what you see at the periphery of your field of view. For a more comprehensive assessment, special equipment might be used to test your visual field. In one such test, you place your chin on a chin rest and look ahead. Lights are flashed on, and you have to press a button whenever you see the light. The lights are bright or dim at different stages of the test. Some of the flashes are purely to check you are concentrating. Each eye is tested separately and the entire test takes 15-45 minutes. These machines can create a computerized map out your visual field to identify if and where you have any deficiencies.