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 how much 'side' vision you have. It is a straightforward test, painless, and does not involve eye drops. Essentially lights are flashed on, and you have to press a button whenever you see the light. Your head is kept still and you have to place your chin on a chin rest. 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 about 15 minutes. Your optometrist may ask only for a driving licence visual field test, which takes 5-10 minutes. If you have just asked for a driving test or the clinic doctor advised you have one, you will be informed of the result by the clinic doctor, in writing, in a few weeks.
Normally the test is carried out by a computerised machine, called a Humphrey. Occasionally the manual test has to be used, a Goldman. For each test you have to look at a central point then press a buzzer each time you see the light.