Study on change in keratometric measurements following application of tear substitutes with varying viscosity in cataract patients

Background: Preoperative keratometry is crucial for accurate intraocular lens (IOL) power calculation during cataract surgery. Dry eye disease (DED) destabilizes the tear film, potentially altering corneal curvature, biometric accuracy, and postoperative refractive outcomes. Influence of artificial tear viscosity on transient corneal regularity warrants investigation. Objectives: To compare baseline keratometric values between normal and dry eyes, assess effect of artificial tears on corneal astigmatism, and evaluate whether drop viscosity influences astigmatic correction. Methodology: A prospective, randomized, observational study was conducted at A.J. Institute of Medical Sciences, Mangalore, from July 2024 to June 2025. Ninety cataract eyes (45 and 45 normal) were classified according to DEWS 2017 criteria. Participants received either high- or low-viscosity artificial tears. Keratometric Corneal astigmatism measured before instillation, at 30 seconds, 2 minutes, and 5 minutes afterward. Paired and unpaired t-tests were used for analysis. Results: Baseline astigmatism was higher in dry eyes than normal eyes (1.58 ± 1.06 D vs. 0.90 ± 1.05 D; p = 0.005). Following tear instillation, dry eyes demonstrated significant reductions of 0.33 D, 0.48 D, and 0.62 D at 30 seconds, 2 minutes, and 5 minutes, respectively (all p < 0.0001). Normal eyes showed minimal, nonsignificant changes. The baseline difference of 0.68 D decreased to 0.03 D at 5 minutes (p = 0.915). High-viscosity drops produced slightly greater reduction than low-viscosity drops (0.47 D vs. 0.43 D), although the difference was not statistically significant. Conclusion: Artificial tears significantly reduced corneal astigmatism in dry eyes, achieving values comparable to normal eyes within 5 minutes. Although high-viscosity drops showed a modest numerical advantage, viscosity did not significantly influence outcomes. Pre-biometry tear supplementation may improve keratometric reliability and IOL power calculation accuracy in cataract patients with DED.