Veronika Röggla1, Christina Leydolt1, Daniel Schartmüller1, Luca Schwarzenbacher1, Elias Meyer2, Claudette Abela-Formanek1, Rupert Menapace3. 1. Department of Ophthalmology and Optometry, Medical University of Vienna, Vienna, Austria. 2. Section for Medical Statistics, Center for Medical Statistics, Informatics and Intelligent Systems, Medical University of Vienna, Vienna, Austria. 3. Department of Ophthalmology and Optometry, Medical University of Vienna, Vienna, Austria. Electronic address: rupert.menapace@meduniwien.ac.at.
Abstract
PURPOSE: To assess the influence of artificial tears of different viscosity on K-readings prior to cataract surgery. DESIGN: Prospective randomized crossover, before-and-after clinical study. METHODS: Setting: Department of Ophthalmology, Medical University of Vienna. PATIENT POPULATION: A total of 123 eyes of 80 patients prior to cataract surgery were assigned to 2 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 (standard deviation = 0.02 mm 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. CONCLUSION: Tear film-stabilizing eye drops prior to keratometry measurements influenced K-readings significantly, especially in dry eyes. A time period of more than 5 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.
RCT Entities:
PURPOSE: To assess the influence of artificial tears of different viscosity on K-readings prior to cataract surgery. DESIGN: Prospective randomized crossover, before-and-after clinical study. METHODS: Setting: Department of Ophthalmology, Medical University of Vienna. PATIENT POPULATION: A total of 123 eyes of 80 patients prior to cataract surgery were assigned to 2 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 (standard deviation = 0.02 mm 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. CONCLUSION: Tear film-stabilizing eye drops prior to keratometry measurements influenced K-readings significantly, especially in dry eyes. A time period of more than 5 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.