Topography is useful for the fitting of contact lenses, particularly in irregular corneas and for rigid lenses. By identifying the curvature of the steepest and flattest areas of the cornea and generating a simulated fluorescein pattern, it can direct the selection of the initial back surface curvature to be tried, thereby reducing the number of trial lenses required. It can also inform the design of custom design lenses.
Corneal irregularity can cause visual loss which is correctable by rigid contact lenses, but not by glasses. Topography is valuable in identifying such cases. In severe cases, such information can be sent to contact lens manufacturers to inform custom lens designs.
Monitoring post-fitting can detect contact lens-induced corneal warpage, due to sustained pressure from the lens in areas of touch. Various patterns can occur, including changes of astigmatism, irregular astigmatism, oblate pattern (flattening centrally and steepening towards the periphery) and a steep-flat pattern with flattening under an eccentric lens with corresponding steepening elsewhere. If the steepening is inferior, this may mimic keratoconus. Warpage tends to reverse after several weeks without lens wear, but if lenses have been worn for many years, the corneal shape may never return to normal. Warpage should have reversed as fully as possible prior to taking measurements for biometry or refractive surgery.
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