Comparison of four intraocular power calculation formulae in keratoconus eyes

Session Details

Session Title: Presented Poster Session: Toric Lenses & IOL Power Calculation

Venue: Poster Village: Pod 1

First Author: : V.Camps SPAIN

Co Author(s): :    R. Fikry   E. Caravaca   F. Labib   V. Mateo   M. Caballero   D. Pinero        

Abstract Details

Purpose:

To analyse and compare the clinical relevance of results obtained theoretically and clinically in keratoconus (KC) eyes using the SRK-T, Hoffer-Q, Holladay I and Haigis IOL formulas. In case of the presence of differences among formulas, the potential contribution of the second corneal surface, among other parameters, to the final predictability achieved in cataract surgery in keratoconus eyes was evaluated.

Setting:

University of Alicante (Spain), Cairo University, Opthalmology department (Cairo, Egypt) and Al Watany Eye Hospital (Cairo , Egypt)

Methods:

The retrospective study included a total of 43 eyes of 22 patients, 16 men and 27 women. IOL powers were calculated using four conventional formulas (SRK-T, Haigis, HofferQ and Holladay 1) using the effective lens position (ELP) defined for each formula and the desired refraction of 0 D (Rdes=0 D). The calculation with the conventional IOL power formulas was performed by implementing them in an Excel software sheet version 2016 for Windows.

Results:

All differences between formulas were statistically significant and clinically relevant. Haigis formula always overestimated than the rest of formulas, with the highest difference between it and the SRK-T and Hoffer Q formulas. The lowest difference was obtained between the Hoffer Q and Holladay 1 formulas. The overestimation by the Haigis formula was higher as the magnitude of the IOL power calculated decreased and the patient became more myopic. Differences between Haigis and Hoffer formulas increased in eyes with deep anterior chambers, steeper anterior and posterior corneal surfaces, and high axial lengths.

Conclusions:

The selection of the IOL power formula in keratoconus eyes needing cataract surgery is crucial as there are statistically and clinically significant differences between formulas, especially in eyes with advanced keratoconus. The most comparable results are provided by the Hoffer Q and Holladay 1 formulas, whereas the Haigis formula provides the most discrepant outcome. Prospective studies must be conducted to evaluate the refractive predictability obtained with all these formulas and to confirm if the Haigis formula is really overestimating and therefore leading to a more significant residual refractive error.

Financial Disclosure:

None