Influence of Artificial Tears on Keratometric Measurements in Cataract Patients

Abstract

To assess the influence of artificial tears of different viscosity on K-readings prior to cataract surgery. Prospective randomized crossover, before-and-after clinical study. Setting: Department of Ophthalmology, Medical University of Vienna. A total of 123 eyes of 80 patients prior to cataract surgery were assigned to 2 groups based on normal and dry eyes. Two native baseline keratometries were followed by instillation of either high- or low-viscosity eye drops. Keratometry was repeated 30 seconds, 2minutes, and 5minutes after instillation. Influence of eye drops of different viscosity in normal and dry eyes on short time K-readings. Repeatability between native baseline measurements was high (standard deviation= 0.02mm in normal and in dry eyes). In normal and dry eyes, a statistically significant increase in measurement variability after instillation of both low-viscosity and high-viscosity eye drops was observed (P < .01). Measurement variability was most pronounced between baseline measurement and 30 seconds and diminished over time. Variability of K-readings appeared higher in dry eyes compared with normal eyes. Astigmatism changed more than 0.5 diopters in 13.2% of normal eyes and 34.4% in dry eyes using eye drops of high viscosity. Tear film-stabilizing eye drops prior to keratometry measurements influenced K-readings significantly, especially in dry eyes. A time period of more than 5minutes should be allowed to pass after instillation of eye drops. The higher the viscosity of the eye drops, the stronger the influence and the longer its persistence.