Influence of Artificial Tears on Keratometric Measurements in Cataract Patients.

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.