Trifocal Non-Toric Or Low-Powered Toric Intraocular Lens Implantation Based On Predicted Posterior Corneal Astigmatism Toric Calculation Formula In Eyes With Low Corneal Astigmatism

To evaluate the refractive outcomes after implantation of trifocal low-powered toric and non-toric intraocular lenses (IOL) in eyes with low preoperative corneal astigmatism.

Memira Eyecenter, Norway. HO Londrina - Hospital de Olhos, Brazil.

Consecutive eyes with low preoperative corneal astigmatism implanted with trifocal IOLs were divided into 2 groups based on toric calculations with predicted posterior corneal astigmatism: non-toric (T00 group) and low-powered toric (T20 group). The main outcome measures were the calculated expected residual astigmatism, postoperative uncorrected distance visual acuity (UDVA), manifest refraction spherical equivalent (MRSE), manifest astigmatism, double-angle plot, and astigmatism linear distribution graph. 

671 eyes were included (T00=468 eyes and T20=203 eyes). Six months postoperatively, there were no statistical differences between groups regarding UDVA (0.00±0.08 LogMAR, P=0.841), MRSE (+0.13±0.30 D, P=0.869) or manifest astigmatism (P=0.055). Ninety-two percent of the eyes presented postoperative manifest astigmatism within 0.50D and a centroid error of 0.03D@79º±0.36D. The calculated expected residual astigmatism presented significant differences between groups (P<0.001), with an opposite pattern: the T00 group showed higher expected residual astigmatism (0.34 ± 0.16D) than postoperative manifest astigmatism (0.26 ± 0.26D), whereas the T20 presented lower expected (0.09 ± 0.08D) than manifest (0.22 ± 0.25D). 

Corneas with preoperative low corneal astigmatism presented a clear benefit of preoperative toric calculations for all trifocal IOL cases. Toric IOL implantation should be performed according to the proposed by the toric IOL calculator.