Assessment Of Rigid Gas Permeable Base Curve Measurements With The Humphrey Topographer.

Background: This research study determines if the base curve of a rigid gas permeable lens can accurately be measured using the Humphrey Topographer. With the advancing technology of automated optical instruments it is evident that the manual instruments will be harder to obtain and access. Few instruments are currently available to accurately measure the base curve of a rigid gas permeable lens, thus the need for alternative methods. Methods: Ten spherical and ten bi-toric RGP lenses were randomly chosen with unidentified parameters. The base curve of each lens was measured using the radiuscope and the Humphrey Atlas Topographer, model991, two trails of each lens were documented. Results: Based on the hypothesis that the two base curve measurements of the RGP lenses are equal, of the lenses tested 90% of the spherical lenses fell within a 95% confidence interval of the hypotheses. For the bi-toric lenses 60% were within the 95% confidence interval. Conclusions: After careful statistical analysis it is apparent that the Humphrey Topographer can accurately assess the base curve of a spherical RGP lenses as compared to the radiuscope. More extensive research is still needed to determine if the bi-toric RGP lenses will be as successful.