A new technique for fitting of tricurve rigid gas-permeable contact lens in penetrating keratoplasty eyes using Scheimpflug imaging

PURPOSE: Rigid gas-permeable (RGP) contact lens fitting after penetrating keratoplasty (PK) is challenging due to significant irregular astigmatism. The aim of the study was to determine a guideline for selecting the initial base curve (BC) of the RGP contact lens fitting in post PK eyes. METHODS: The data of patients who had tricurve RGP contact lens fitting post PK were collected retrospectively. The following data were collected: best-corrected visual acuity with glasses and contact lenses; contact lens parameters which included the BC and diameter; corneal topography parameters which included steep keratometry value (K), flat-K, and mean-K; and anterior best fit sphere (BFS) measured using Scheimpflug imaging. RESULTS: The median age of the 40 subjects (46 eyes) who met the inclusion criteria was 37.5 years (IQR 26.7–45.5). The spherical equivalent was –3.00 diopter (D) (–8.31 to –1.56). The median steep-K, flat-K, and mean-K in them were 6.76 mm (6.28–7.07), 7.78 mm (7.37–8.14), and 7.26 mm (6.93–7.46), respectively. The median anterior BFS value of the transplanted cornea was 6.96 mm (6.6–7.37). The median BC of the final RGP lens was 7.0 mm (6.7–7.23) and the median diameter was 9.8 mm (9.4–10.4). Among all the Scheimpflug imaging parameters, the BFS correlated well with the final BC of the RGP contact lens dispensed (R 0.742, P < 0.0001). CONCLUSION: The anterior corneal surface BFS value can be used as a reference in selecting the initial BC of tricurve RGP contact lens to achieve the best fitting and reducing the chair time of patients after PK.