The refractive index of contact lens saline solutions

PurposeThe aim of this study was to measure the refractive index of three readily available contact lens saline solutions in order that these values could be used in a calculation to convert back vertex power measured in saline to its corresponding power in air.MethodUsing an automatic digital refractometer, measurements were made daily for 31 days at 20 °C and at a wavelength of 589.3 nm of the refractive index of fifteen bottles from different manufacturing batches of each of the three saline solutions.ResultsFor AMO LENS PLUS™ OcuPure™, BAUSCH & LOMB Sensitive Eyes™ Plus Saline Solution and Sauflon saline, the mean values of refractive index were 1.33458, 1.33465 and 1.33470, respectively. The standard deviation for each solution was 0.00001 and the range of the measured values of refractive index of the three solutions over the test period did not exceed 0.00005.ConclusionsIt is proposed that when calculating back vertex power in air from measurements made in a wet cell that refractive index values for AMO LENS PLUS™ OcuPure™, BAUSCH & LOMB Sensitive Eyes™ Plus Saline Solution and Sauflon saline of 1.3347, 1.3348 and 1.3348, respectively be used for focimeters operating at a wavelength of 587.56 nm and values of 1.3361, 1.3362 and 1.3362, respectively when a wavelength of 546.07 nm is used.