Comparison of Impact of Balanced Salt Solution and Cohesive-Dispersive Viscoelastic on Intraoperative Aberrometry Measurements
A small previous study noted a difference in spherical equivalent (SE) between intraoperative aberrometry measurements taken after inflating the eye with balanced salt solution (BSS) vs. viscoelastic. This evaluation was undertaken to determine whether the difference in measurements is consistent enough to be incorporated into future nomograms.
Analysis of refractive outcomes in 54 eyes undergoing cataract surgery. After phaco, eyes were inflated to 21 mmHg using BSS. An aphakic intraoperative aberrometry measurement and IOL power recommendation were obtained. All BSS was removed and the eyes were reinflated to 21mmHg with the same cohesive-dispersive viscoelastic used during phaco (Discovisc, Alcon). A second aphakic measurement was obtained. Outcomes include postoperative visual acuity at 1 month and differences in SE and lens power recommendation between the two measurements, as well as the difference in prediction error between the two power recommendations.
Mean aphakic SE was 11.73 ± 3.25 D with the BSS measurements and 10.85 ± 3.50 D with the Discovisc measurements, a mean difference of 0.76 ±0.28 D. The mean IOL power recommendation was 20.12 ± 2.87 D with BSS and 19.73 ± 2.93 D with Discovisc, a mean difference of 0.52 ± 0.27 D. Mean absolute value of the prediction error (MAVPE) was 0.30 ± 0.28 D for BSS measurements compared to 0.58 ± 0.48 D for the Discovisc measurement.
Aphakic SEs obtained with a cohesive-dispersive viscoelastic differ from and are lower than those obtained with BSS. Given that the differences are consistent, as evidenced by the standard deviation, it seems reasonable that a nomogram could be developed so that a cohesive-dispersive viscoelastic could be used for intraoperative aberrometry measurements.