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Optimizing intraocular lens power calculation using adjusted conventional keratometry for cataract surgery combined with Descemet membrane endothelial keratoplasty

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First Author: R.Diener GERMANY

Co Author(s):    J. Lauermann   M. Treder   N. Eter   M. Alnawaiseh           

Abstract Details

Purpose:

To evaluate intraocular lens (IOL) power calculation using adjusted conventional keratometry (K) according the postoperative posterior to preoperative anterior corneal curvature radii ratio (PPPA-ratio) for eyes with Fuch´s dystrophy undergoing cataract surgery combined with Descemet membrane endothelial keratoplasty (Triple DMEK).

Setting:

Department of Ophthalmology, University of Muenster, Germany

Methods:

A fictitious refractive index (FRI) was calculated based on the PPPA-ratio in 50 eyes undergoing TripleDMEK, determined by pre- and postoperative Scheimpflug-imaging. Adjusted corneal power was calculated in every eye with Eom´s Adjustment Method: K values determined by the IOLMaster were converted to adjusted anterior corneal radius using the mean FRI. Posterior corneal radius was calculated with the mean PPPA-ratio. Adjusted corneal power was determined based on the calculated corneal radii and thick lens formula. Arithmetic error using the Haigis and SRK/T formulae based on the adjusted corneal power was compared with that based on conventional K measurements.

Results:

Calculated mean PPPA ratio and FRI was 0.805 and 1.3272. Mean refractive error based on conventional K was in the hyperopic direction (Haigis formula: 0.77±1.12D; SRK/T formula: 0.54±1.05D) and significant higher (P<0.001) than that based on adjusted corneal power (0.07±1.09D and 0.02±1.13D). Percentage of eyes with a hyperopic shift >0.5D calculated with adjusted corneal power was reduced from 62% to 13% (Haigis) and 54% to 13% (SRK/T). Proportion of eyes with a prediction error of ±0.5D was significantly smaller using conventional K in the Haigis (28%) and SRK/T formula (26%) than that obtained using adjusted corneal power (44% and 40%).

Conclusions:

IOL power calculation using adjusted conventional K based on the postoperative posterior to preoperative anterior corneal curvature radii ratio in eyes with FECD undergoing triple DMEK enables more accurate refractive outcomes than IOL power calculation using conventional K. Eom´s Adjustment Method being based on FRI (1.372) and PPPA-ratio (0.805) can be used to reduce the risk of a hyperopic shift after TripleDMEK.

Financial Disclosure:

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