Topography is used in topographical fitting to create what?

• A. A fixed, non-adjustable lens
• B. An alignment fitting relationship
• C. A diagnostic trial only
• D. A lens that cannot be adjusted

Answer: (B)

Topography data reveal the exact shape of the corneal surface, including how steep or flat it is and where curvature changes. In topographical fitting for gas-permeable lenses, that information is used to design a lens whose base curve and peripheral geometry closely match the cornea. The result is an alignment fitting relationship, where the lens sits in even contact with the cornea, centers well, and maintains a stable tear lens with appropriate movement. Because the lens design can be customized based on the map—adjusting base curve, diameter, and peripheral curves—it is not about a fixed or non-adjustable lens, nor is it limited to a diagnostic trial.