Piggyback lenses are used by many practitioners as a means of improving the acuities of patients with irregular astigmatism. This modality consists of a soft lens carrier with an overriding rigid lens. The purpose of our study was to determine whether the power of the soft lens carrier would impact the base curve of the rigid lens required. Two subjects were fit with Ciba Night and Day contact lenses 8.4/13.8 in powers of +0.25, +3.00, and +6.00. Topographical corneal maps were taken using the Medmont videokeratoscope of each patient in each of the lenses in addition to one with no lenses at all. It was determined that, in fact, the power of the soft lens does affect the "effective" corneal curvature in which the rigid lens needs to be fit. 5
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