Comparative Refractive Accuracy Of Kane For Keratoconus, Barrett True-K For Keratoconus, And Srk/T Formulas In Cataract Surgery Eyes With Keratoconus
Published 2026 - 44th Congress of the ESCRS
Reference: POCAT626 | Type: Free paper | DOI: 10.82333/6yew-v012
Authors: Ms Aki Tanimura* 1 , Dr So Goto 1 , Dr Naoyuki Maeda 2 , Dr Yoshinori Oie 1 , Dr Shizuka Koh 3 , Dr Takeshi Soma 1 , Dr Akihiko Shiraki 1 , Prof. Dr Kohji Nishida 4
1Department of Ophthalmology,Graduate School of Medicine, The University of Osaka,Suita, Osaka,Japan, 2Ophthalmology,Kozaki Eye Clinic,Osaka,Japan, 3Department of Ophthalmology,Graduate School of Medicine, The University of Osaka,Suita, Osaka,Japan;Ophthalmology,Department of Innovative Visual Science, The University of Osaka Graduate School of Medicine,Osaka,Japan, 4Department of Ophthalmology,Graduate School of Medicine, The University of Osaka,Suita, Osaka,Japan;Ophthalmology,Intergrated Frontier Research for Medical Science Division, Institute for Open and Transdisciplinary Research Initiatives,Suita, Osaka,Japan
Purpose
To compare the refractive prediction accuracy of Kane for keratoconus formula(Kane-KC), Barrett True-K for keratoconus formula(BTK-KC), and SRK/T formula in keratoconus eyes undergoing cataract surgery.
Setting
This single-center clinical study was conducted at The University of Osaka Hospital, Osaka, Japan. Medical records of consecutive patients who underwent cataract surgery between March 2017 and November 2025 were reviewed.
Methods
This retrospective study included keratoconus eyes undergoing cataract surgery. Intraocular lens (IOL) power was calculated using Kane-KC, Barrett True-K, and SRK/T formulas. Prediction error (PE) was defined as 1-month postoperative subjective spherical equivalent minus target refraction. Outcomes included mean PE, standard deviation (SD), median absolute error (MedAE), root square mean absolute error (RSMAE), and proportions within ±0.5 D and ±1.0 D. Subgroup analysis was conducted according to the Amsler-Krumeich classification.
Results
Fifty-seven keratoconus eyes (29 female, 28 male) were analyzed. Mean age was 64.5±11.6 years, mean axial length was 26.2±2.1 mm, and mean keratometry was 48.4±4.3 D. According to Amsler–Krumeich classification, 22eyes were stage1, 20 stage2, 7 stage3, and 8 stage4. Mean PE did not differ significantly among formulas (p=0.67). MedAE was 0.85 D for Kane-KC, 0.97 D for BTK-KC, and 1.08 D for SRK/T. RSMAE was 1.63 D, 1.71 D, and 1.94 D, respectively. Kane-KC showed significantly lower MedAE and RSMAE than SRK/T (p < 0.05, respectively). The proportion of eyes within ±1.0 D were 59.6% for Kane-KC, 52.6% for BTK-KC, and 47.4% for SRK/T(p = 0.13). Prediction error variability increased with advancing KC severity based on Amsler-Krumeich staging.
Conclusions
Although mean PE was comparable among formulas, keratoconus-specific algorithms demonstrated superior refractive precision compared with SRK/T formula. In particular, Kane-KC achieved significantly lower MedAE and RSMAE compared with SRK/T. Refractive predictability decreased with increasing keratoconus severity. Stage-based counselling is essential when planning cataract surgery in keratoconus eyes.