Knowing the shape of the cornea in more detail than just the central readings as determined with the keratometer can be very helpful in diagnosing corneal conditions such as keratoconus, following corneal curvature changes, pre- and post-surgical evaluations, and in some cases in fitting contact lenses.
Computerized videokeratography has become available and popular. Most of these instruments digitize an image of a ring pattern from the surface of the cornea and then construct topography maps. They cover the central 8 to 10 mm of the cornea. They are limited in that they do not measure to the limbus. They must be properly focused and aligned for accurate results.
