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The efficacy of different biometry formulae in stable ectatic corneas

Poster Details

First Author: F.Emad Labib EGYPT

Co Author(s):    M. Roshdy   S. Wahba   R. Fikry              

Abstract Details

Purpose:

To study the efficacy of different biometry formulae used in Intraocular lens (IOL) power calculation for patients with stable keratoconus or post Lasik ectasia.

Setting:

Al Watany Eye Hospital, Cairo, Egypt.

Methods:

A retrospective comparative study included 38 eyes of 24 patients with stable keratoconus or post Lasik ectasia, who underwent cataract extraction. Group A included 21 eyes implanted with non-toric IOL and group B 17 eyes with toric IOL. The spherical equivalent (SE) prediction error, safety index and efficacy index of different formulae were calculated.

Results:

Mean age was 46.9�Â�±14.5 years,axial length was 25.98�Â�±2.42mm,anterior chamber depth was 3.65�Â�±0.43,thinnest corneal thickness was 428.8�Â�±54.8�Â�µm, keratometric reading was 46.48 �Â�±4.66D,topographic astigmatism was 3.53�Â�±2.54D. Postoperative SE was -0.69�Â�±1.18D and cylinder -2.22�Â�±1.79D (-2.96�Â�±1.85D in Group A and -1.35�Â�±1.27D in Group B, P=0.0046).Absolute SE prediction error wasn�â�€�™t statistically significant between formulas:Haigis (0.91�Â�±0.77D), SRK-T (1.01�Â�± 0.79D), Hoffer Q (0.95�Â�±0.83D),Barrett (1.07�Â�±0.82D),Holladay1 (1.02�Â�±0.78D),P>0.05.The Holladay and Hoffer Q formulas giving more hyperopic results than the others (P<0.05).Surgeries showed safety index of 1.44�Â�±0.83 and efficacy index of 1.04�Â�±0.68.

Conclusions:

In stable ectatic corneas, cataract extraction and IOL implantation showed good safety and efficacy indices. All formulas have comparable accuracy, although Holladay and Hoffer-Q gave more hyperopic outcomes. Toric IOLs calculation based on Barrett formula significantly reduced the postoperative astigmatism.

Financial Disclosure:

travel has been funded, fully or partially, by a competing company

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