Findings of a study determining the prediction error in the magnitude of residual astigmatism after cataract surgery with a toric intraocular lens (IOL) suggest that use of intraoperative wavefront aberrometry for toric power selection could enhance the refractive outcome in a large subset of eyes.
The study included 50 eyes of 38 patients implanted with a toric IOL (SN6ATx; AcrySof IQ Toric IOL, Alcon Laboratories). In all cases, the toric power of the implanted IOL was determined using an intraoperative wavefront aberrometer (ORA System, Alcon Laboratories). The residual astigmatism predicted by the device was noted.
In addition, IOL power calculation was performed for all eyes with the toric IOL manufacturer’s online calculator that uses the Barrett Toric Algorithm, a nomogram that theoretically accounts for posterior corneal astigmatism. Using the subjective refraction measured at 3 months postoperatively, the predicted residual astigmatism for the implanted toric IOL was back-simulated using the toric IOL calculator.
For the main outcome analysis, the difference vector was calculated for each prediction method by subtracting the predicted residual astigmatism vector from the observed postoperative astigmatism vector.