Effect of corneal vital dyes on pachymetry measured by dual Scheimpflug technology

PurposeThis study evaluated and compared changes in pachymetry measurements at different times after applying riboflavin 0.25%, lissamine green 0.5%, fluorescein 2%, and fluorescein 0.25% - lidocaine HCl 4% eye drops.MethodsCorneal pachymetry was assessed in thirty healthy volunteers (60 eyes) using a Galilei G6^® Dual Scheimpflug topographer. Baseline measurements were taken with and without saline. Thickness was measured at 1, 5, and 15 min after dye application.ResultsSignificant increases (p < 0.001) in Central Corneal Thickness (CCT) were observed following riboflavin instillation (N = 60, at 1 min: 17 ± 7.1 µm; at 5 min: 7.1 ± 6.9 µm), fluorescein 0.25% (N = 59, at 1 min: 14.8 ± 14.1 µm; at 5 min: 9.4 ± 7.4 µm; at 15 min: 5.2 ± 6.7 µm), and fluorescein 2% (N = 10, at 1 min: 20 ± 5.7 µm; at 5 min: 18.8 ± 7 µm; at 15 min: 11.2 ± 8.4 µm). There was a high number of artifacts in the measurements with 2% fluorescein (48 eyes), and only three patients showed no artifacts. Lissamine green (N = 58) did not significantly affect pachymetry measurements.ConclusionsRiboflavin 0.25% and fluorescein 0.25% temporarily overestimated pachymetry. Fluorescein 2% caused excessive artifacts, compromising reliability. Lissamine green 0.5% showed no influence in pachymetry. Characteristics from vital dyes should be considered according to programmed examinations when using a Dual Scheimpflug topographer.