Comparison of the predicted target refraction and the postoperative refraction using two different calculators for toric intraocular lens calculation

Session Details

Session Title: Pseudophakic IOLs: Toric I

Session Date/Time: Saturday 10/09/2016 | 16:00-18:00

Paper Time: 16:12

Venue: Hall C2

First Author: : C.Kern GERMANY

Co Author(s): :    A. Sakhel   K. Kortam   F. Raabe   A. Wolf   S. Priglinger   M. Wolfgang     

Abstract Details

Purpose:

To compare two calculators for toric intraocular lens (IOL) calculation by comparing the predicted target refraction (TR) and the postoperative refraction (PR) with regard to the predicted required toric cylinder power (TCP).

Setting:

Retrospective case series, Single Centre Study, Department of Ophthalmology, University Hospital Munich

Methods:

49 Eyes of 42 patients undergoing co-axial micro-incision cataract surgery (CoMICS) and phacoemulsification by one experienced surgeon with an estimated surgical induced Astigmatism (SIA) ≤0.5 D followed by implantation of a toric intraocular lens (Zeiss Torbi 709M) calculated by the Zeiss calculator (ZCalc). For all biometric analyses the Zeiss IOL Master 500 was used. The error between the TR and the PR was verified by Wilcoxon analysis. The predicted required TCP between the ZCalc and the Barrett calculator was compared using again Wilcoxon statistical testing. Moreover, we performed a subgroup analysis regarding the TCP for Patients with With-the-Rule (WTR) astigmatism.

Results:

Our Analysis showed a significant difference between the spherical equivalent (SE) of TR and PR (p = 0.01) in all patients. Compared to the selected TR we reached mean postoperative under-correction in the SE of +0.28 D (SD ± 0.42D). Comparing the TR and PR in patients with WTR astigmatism (n=30) study data result in no significant postoperative refractive error (p>0.05). There was no difference between the predicted required TCP between the ZCalc and the Barrett calculator (p>0.05). Regarding the subgroup of patients with a postoperative error ≤ 0.5 D or >0.5 D we observed no difference of the predicted TCP between the two calculators (p>0.05).

Conclusions:

The deviation between TR and PR was within tolerable limits of ± 0.5 D despite the significant postoperative under-correction of 0.28 D. Regarding only patients with WTR astigmatism, the effect did not reach statistical significance. According to the Baylor Nomogram WTR astigmatisms tend to over-correction which could lower our significant tendency for under-correction. In our study the Barrett calculator considering simulated posterior corneal astigmatism with IOL Master 500 values did not have a significant advantage over a standard calculator in predicting toric IOL power.

Financial Disclosure:

NONE