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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


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


Al Watany Eye Hospital, Cairo, Egypt.


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.


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.


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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