Posters

Comparison of corneal power measurement for intraocular lens calculations in previously myopic patients who have undergone laser refractive surgery

Poster Details

First Author: T.Jenyon UK

Co Author(s):    P. Mandal   A. Bansal                 

Abstract Details

Purpose:

There is no current consensus on the most accurate method to calculate corneal power in patients who have undergone previous laser refractive surgery.  We looked at two different methods of calculating corneal power that are readily available in most units.  The IOLMaster 500 (Carl Zeiss Meditec) optical keratometry readings were compared to the Pentacam (Oculus) derived Equivalent K Readings (EKR) using the 4.5mm zone.  The purpose of this study was to determine the most accurate method of keratometry for estimating IOL power in this group of post refractive patients.

Setting:

Eye Unit, University Hospital of Coventry and Warwickshire, UK.

Methods:

Retrospective review of 11 sequential eyes from 11 patients, who underwent cataract surgery after prior myopic correction with LASIK or PRK.  Pre-operatively corneal power was measured using the IOLMaster and the Pentacam.  These values were used to calculate the suggested IOL power using the online ASCRS calculator average. Following cataract surgery, the postoperative deviation from predicated refractive outcome was used to retrospectively calculate the optimum IOL power for achieving planned refractive outcome.   The two methods of measuring corneal power were then compared to the optimum IOL power and the most accurate method determined retrospectively.

Results:

The average optimum IOL was 18.17D. The average IOL power as suggested using the IOLMaster K readings was 19.27D compared to 20.26D using the Pentacam derived 4.5mm EKR.   The two methods of measuring corneal power were significantly different (p = 0.00013).  Both methods were significantly different from the calculated optimum IOL power (over estimating IOL power in every case) but the IOLMaster optical Ks gave a more accurate result.

Conclusions:

This small retrospective study suggests that the Zeiss IOLMaster optical Ks give more accurate IOL power recommendations when used as part of the ASCRS IOL calculator.  Both methods suggest higher power IOLs leading to more myopic outcome than predicted.  In the absence of any other methods we would recommend using the Zeiss IOL Master optical Ks over the Pentacam 4.5mm EKR in post refractive surgery intraocular lens calculations.

Financial Disclosure:

None