LAUSR

PURPOSE Assessing the influence of artificial tears of different viscosity on K-readings prior to cataract surgery. DESIGN Prospective randomized cross-over, before-and-after clinical study METHODS: Setting: Department of Ophthalmology, Medical University Vienna PATIENT POPULATION: A total of 123 eyes of 80 patients prior to cataract surgery were assigned to two groups based on normal and dry eyes. INTERVENTION Two native baseline keratometries were followed by instillation of either high- or low-viscosity eye-drops. Keratometry was repeated 30 seconds, 2 minutes and 5 minutes after instillation. MAIN OUTCOME MEASURES Influence of eye-drops of different viscosity in normal and dry eyes on short time K-readings. RESULTS Repeatability between native baseline measurements was high (SD=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<0.01). 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 to 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. CONCLUSION Tear film stabilizing eye-drops prior to keratometry measurements influenced K-readings significantly, especially in dry eyes. A time period of more than five minutes 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.