Purpose: To assess the refractive accuracy of different formulas for intraocular lens (IOL)power calculation in eyes with keratoconus. Setting: IRCCS Fondazione Bietti, Rome, Italy. Design: Multicenter retrospective interventional study. Methods: A consecutive series of eyes with keratoconus that had cataract surgery were evaluated. Keratometry, anterior chamber depth, and axial length were measured preoperatively with optical biometry; IOL power was calculated with the Barrett Universal II, Haigis, Hoffer Q, Holladay 1, and SRK/T formulas. Subjective refraction was assessed at 1 month. The mean prediction error (PE), median absolute error (MedAE)and percentage of eyes with a PE within ±0.50 diopters (D), ±0.75 D, and ±1.00 D were calculated. Results: The final spherical equivalent was −0.52 D ±1.61 (SD). In the whole sample (41 eyes), the mean PE was positive (hyperopic surprise)with all formulas; the lowest PE (0.91 D)and MedAE (0.62 D)were obtained with the SRK/T formula. In stage I eyes (n = 21), the MedAE ranged between 0.43 and 0.91 D; the SRK/T formula achieved the lowest MedAE and the highest rate of eyes with a PE within ±0.50 (61.9%). In stage II eyes (n = 13), the MedAE ranged between 0.75 D and 1.50 D; the SRK/T formula achieved the lowest MedAE and the highest rate of eyes with a PE within ±0.50 (30.8%). In stage III eyes (n = 7), the MedAE was higher than 2.50 D with all formulas. Conclusions: In keratoconus eyes, all formulas led to a hyperopic refractive outcome. The SRK/T was the most accurate formula. The results were worse in advanced stages of the disease.
ASJC Scopus subject areas
- Sensory Systems