Abstract: Aim: To describe the correlation between base curve (BC) of RGP trial lens fitting and topographic findings. Methods: 245 eyes of 200 keratoconus patients (97 females and 103 males), who underwent RGP CL fitting, included in this study. Wavelight Advance Topographer (Oculyzer -II) was used to measure corneal curvature. All participants were divided in to 7 groups based on Sim-k reading. Statistical analysis: Pair t- test. Result: Significant correlation found between final lens BC and Sim-k reading of Oculyzer-II. For group 5 & 7, BC= steep sim-k. For group 2, BC= average sim-k. For Group 1,3,4& 6, BC= flat sim-k. Conclusion: The development of new theory for RGP lens fitting enables eye care professional to achieve an optimum-fit in a shorter period of time by reducing the no of trials. The customary lens fitting methods are suggested to be replaced by the correlation found in this study.