CHANGES IN COMPUTERIZED VIDEOKERATOGRAPHY INDUCED BY ARTIFICIAL TEARS

Purpose: To analyze the effect of several standard artificial tear pre parations on computerized videokeratograhic measurements. Setting: Cul len Eye Institute, Baylor College of Medicine, Department of Ophthalmo logy, Houston, Texas, USA. Methods: We evaluated one eye each in 18 no rmal volunteers. Using the EyeSys Corneal Analysis System(TM) (EyeSys Technologies), we obtained corneal topographic measurements at baselin e and 0.5, 1, 2, 3, 4, 5, 6, 8, and 10 minutes after instillation of t he following preparations: balanced salt solution, Tears Naturale(R)II , Tears Naturale Free(R), Cellufresh(R), Celluvisc(R), HypoTears(R), a nd HypoTears(R)PF. We analyzed changes in curvature of the keratograph ic rings at radii 1 to 5 mm and changes in keratometric-equivalent ast igmatic power and meridian. Results: A[I preparations except HypoTears and Tears Naturale II induced statistically significant, time-depende nt changes in mean corneal power in the central 5 mm corneal zone comp ared with baseline measurements (P<.05). The relationship between chan ge in dioptric power over time varied with preparation type and was no nlinear in nature. In all cases, the mean induced change was less than or equal to 0.5 diopter. Except for Celluvisc, tear administration pr oduced minimal changes in the values of corneal astigmatic power or me ridian. Conclusion: When performing serial measurements of mean cornea l power, the greatest consistency was achieved with no tears or with i nstillation of HypoTears or Tears Naturale II.