Abstract
Purpose :
To compare the Barrett formula predicted posterior corneal astigmatism with the Scheimpflug camera (Pentacam) directly measured posterior corneal curvature, in toric cataract surgery biometry, utilizing the Barrett Toric Calculator, and the resultant selection of Toric IOL for each group.
Methods :
A retrospective clinical study was conducted to determine the comparison of the predicted posterior corneal astigmatism versus the measured posterior corneal astigmatism. A clinical series of eyes being measured for cataract surgery with toric IOL placement was retrospectively studied. All eyes were measured with the scheimpflug camera (Pentacam) for posterior corneal astigmatism. The Barrett Toric Calculator was utilized. An analysis of the data for posterior corneal astigmatism was obtained both by the Barrett predicted posterior corneal astigmatism as well as the Pentacam measured posterior corneal astigmatism. The raw difference in posterior corneal astigmatism amounts was compared between the predicted and measured groups. Also analyzed was the final IOL toricity amount suggested for implantation between both the predicted and measured posterior corneal astigmatism groups.
Results :
The preoperative biometry of 28 eyes undergoing toric calculations for cataract surgery was randomly selected and analyzed. Direct measurement of the posterior corneal astigmatism versus the predicted corneal astigmatism varied in 27 of 28 cases. Except for the one eye that had the exact same astigmatism measured vs predicted, this variability ranged from 0.01D to 0.33D. On average, the predicted corneal astigmatism using the Barrett Toric Calculator was 0.135D different than the direct measurement with Pentacam with a 95% confidence interval of (.099,.172) and p value of 3.08*10-8. The differences between measured and predicted posterior corneal astigmatism resulted in a different IOL recommendation for 4/28 eyes (14%). In 3 of these eyes, the measured astigmatism resulted in a reduction in the amount of cylinder recommended in the IOL. In the other case, it resulted in an increase in the recommended cylinder.
Conclusions :
Measurement of the posterior corneal curvature with Pentacam results in a different toric IOL selection with the Barrett toric calculator in a significant percentage of patients.
This is a 2020 ARVO Annual Meeting abstract.