Accuracy of keratoconus-specific formulae compared to standard formulae for intraocular lens power calculation in patients with keratoconus

Objective

To compare the accuracy of keratoconus-specific formulae for nontoric and toric intraocular lenses in eyes with keratoconus undergoing cataract surgery.

Design

Consecutive retrospective case series.

Participants

Patients with keratoconus who underwent cataract surgery.

Methods

A retrospective chart review was conducted on cataract surgeries performed by the Cornea Service in the Department of Ophthalmology and Visual Sciences of the University of British Columbia from 2000 to 2023. The Kane keratoconus, Kane, Barrett Universal 2, Barrett True K, SRK II, SRK/T, Hoffer Q, Holladay I, EVO, Hill RBF and Hoffer QST, and Pearl DGS formulae were calculated. The postoperative mean absolute error (MAE) and mean prediction error (MPE) were calculated for each formula.

Results

A total of 133 eyes from 88 patients were eligible for inclusion in the study, 113 from 74 patients received nontoric IOLs, and 20 from 14 patients received toric IOLs. Pearl DGS had the most myopic MPE of −0.51 ± 1.04, which was statistically significant (p < 0.001) compared to all other formulae. There were no statistically significant differences in the MPE and MAE of the Kane keratoconus, Kane, Barrett Universal 2, Barrett True K keratoconus-specific formula, SRK II, SRK/T, Hoffer Q, Holladay I, EVO, Hill RBF and Hoffer QST formulae (p > 0.05).

Conclusion

There was no difference in IOL power estimation accuracy with keratoconus-specific formulae compared to conventional formulae for cataract surgery in KC patients. The IOL power estimation in KC remains significantly less accurate compared with non-KC patients.