NOV 14, 2019
Cataract/Anterior Segment, Refractive Mgmt/Intervention
This retrospective review of 2 prior toric IOL studies compared the use of intraoperative aberrometry with current-generation formulas for eyes undergoing toric IOL implantation.
Investigators studied 132 eyes receiving 2 different toric IOLs: SN6ATx (Alcon) and Tecnis Symfony Toric (Johnson & Johnson). They compared expected residual refractive sphere and cylinder using intraoperative wavefront aberrometry with the ORA or preoperative spherical power calculations using the Barrett Universal II for the SN6ATx and the Haigis formula for the Symfony. Astigmatic power was calculated using the Barrett Toric calculator for the SN6ATx lens and the Johnson & Johnson’s Surgical Vision Toric Calculator for the Symfony.
At 3 months, the percentage of eyes with expected spherical equivalent refractions within 0.25 and 0.5 D of target was higher in the preoperative calculations group, at 87% and 65% compared with 78% and 68% in the aberrometry group, respectively (P=0.02 and P=0.05).
Seventeen eyes had a spherical equivalent of more than 0.5 D off target; intraoperative aberrometry would have led to better outcomes than preoperative calculations in 2 of these cases. When looking at the astigmatism power, the preoperative calculation group had a higher percentage within 0.5 D compared with the aberrometry group (94% vs. 58%; P<0.001).
This was a retrospective analysis that did not include any eyes are that are typically considered to have a higher chance of inaccurate preoperative IOL calculations, such as post-LASIK eyes. It is possible if these eyes were included, the results for intraoperative aberrometry group would have been better.
In prior studies, intraoperative aberrometry has been considered to raise the accuracy of sphere and cylinder to 82% and 90%, respectively, over the older methods of IOL calculations that yield 75% and 76% of cases within 0.5D. This study suggests that newer methods of spherical and toric calcuations that incorporate expected posterior corneal astigmatism improve preoperative accuracy, and thus may limit the benefits of intraoperative wavefront aberrometry. A major limitation is that this study included no eyes with previous keratorefractive surgery, and wavefront aberrometry would likely perform better due to the lower accuracy of preoperative calculations in these cases.