Corneal topography and computerized contact lens-fitting modules (Englisch)

AbstractContact lens fitting by videokeratoscopy or other corneal mapping techniques offers a number of advantages over traditional keratometry and fluorescein pattern interpretation. The ability of these instruments to quantitate midperipheral corneal topography allows a more accurate determination of the many bearing and clearance points of the contact lens. The major question facing practitioners is how to interpret the corneal maps into usable contact lens-fitting information. Also, once the maps have been translated, can the information be numerically described within the software of the instrument? The ideal contact lens-fitting module should follow a series of logical steps similar to the thought process the practitioners use to determine the optimum lens fit. We have identified two fundamental steps in the fitting process that form the cornerstone to any topographic fitting module; these are that (1) a bearing area should be present along the horizontal meridian approximately 3–4 mm from center, and (2) the lens should maintain unobstructed movement along the vertical meridian. The appropriate radii to achieve these fitting objectives can be systematically evaluated from the corneal map. The computer can then identify if the chosen base curve will permit the desired bearing and clearance points on the cornea.