Toric Intraocular Lens Calculations With The Barrett Calculator: A Comparative Analysis Of The Calculator With And Without The Integrated K Option

To evaluate the accuracy of the Barrett Integrated K (IK) toric calculator in comparison with the standard Barrett toric calculator using both predicted and measured posterior corneal astigmatism (PPCA and MPCA, respectively).

Ophthalmology Department, Rabin Medical Center, Petach Tikva, Israel.

Consecutive cases of patients who underwent cataract extraction with implantation of a toric IOL were retrospectively reviewed. Only eyes with final best-corrected visual acuity of 20/40 or better were included. Errors in the predicted postoperative refractive astigmatism were calculated for the Barrett toric calculator with and without the IK tool using PPCA and MPCA. Using vector calculation, the predicted postoperative refractive astigmatism was compared with the actual postoperative refractive astigmatism to give the prediction error. The median absolute error, the mean centroid error and the percentage of eyes with a prediction error within 0.50D, 0.75D and 1.00D were calculated for each method.

The study included 78 eyes of 62 patients. The mean centroid prediction error with Barrett’s PPCA (0.11 ± 0.81D @ 80°) was significantly different compared with the MPCA (0.09 ± 0.81D @ 59°, p=0.011) and the IK-MPCA (0.07 ± 0.80D @ 50°, p=0.048) calculators. In addition, a significant difference between the IK-PPCA (0.08 ± 0.80D @ 80°) and IK-MPCA was found (p=0.014). The median absolute prediction error ranged from 0.56D using the IK-PPCA formula to 0.61D using the PPCA formula, with no significant differences between the four calculation versions. No significant differences were seen between the calculators in the predictability rates within 0.50D, 0.75D and 1.00D.

The Barrett Integrated K toric calculator yielded comparable outcomes to the Barrett calculator which uses only a single device for anterior corneal evaluation. Although differences in the mean centroid errors were found, they were clinically insignificant and predominantly seen in the axis of the error of the predicted astigmatism. These minor differences were mainly attributed to the incorporation of the MPCA in the calculation.