Variations in keratometric values (K-value) after administration of three different eye drops: effects on the intraocular lens calculations in relation to cataract surgery

Purpose: To investigate the variance in keratometric (K) values after administration of different eye drops (three tested), and the effects on intraocular lens (IOL) power calculations in relation to standard cataract surgery. Methods: A prospective intervention study (pilot study) on 38 participants (22 women, 16 men, 58–88 years) undergoing 57 cataract surgeries. Three keratometries on each eye were performed: a baseline (‘standard’) keratometry about 9 weeks preoperatively, and two on the operation day; a ‘dry’-measurement before interventions and a ‘wet’-measurement after applying one of three eye drops (saline, Systane Ultra^®, or Systane Complete^®). All standard cataract operations were uneventful. Variabilities in K-values, spherical equivalents (SEQs) for IOL power calculations (Barrett TK Universal II) and subjective manifest refractions (SRs) 6 weeks postoperatively were compared between groups. Results: The ‘wet’ K-values had a similar variability to those of the ‘standard’ and ‘dry’ K-values (p > 0.05, anova on ranks). The mean paired differences in K-measurements between groups ranged within a small interval from −0.0107 to 0.0096 mm. After comparing the SEQ predictions with SR-measurements, the most precise IOL calculation was achieved after administration of a saline eye drop, but the precision was not statistically improved compared to the other drop modalities. Conclusion: The variability in K-values was not significantly changed by administration of any of the different eye drops tested, suggesting that artificial eye drops do not impact the keratometry or IOL power prediction.