Safety of refractive surgery in patients diagnosed with keratoconus through biomechanical and tomographic properties by an artificial intelligence algorithm

Abstract

Purpose : To evaluate the risk of ectasia of laser-assisted in situ keratomileusis (LASIK) in patients diagnosed with subclinical keratoconus (SCKC) and keratoconus (KC) using the Tomographic Biomechanical Index (TBI) on the Pentacam and Corvis ST (Oculus, Wetzlar, Germany).

Methods : A retrospective study of patients who had LASIK surgery between the years 2020 and 2022 was performed. All patients underwent clinical examination in the slit-lamp and biomechanical and tomographic data collected using the Pentacam and Corvis ST. Patients were divided into three groups based on TBI: Normal (0 and 0.4), SCKC (0.41 and 0.78) and KC (TBI>0.78). All patients had a residual stromal bed (RSB) over 290 microns and a percentage tissue altered (PTA) under 40%. Patients with keratoconus diagnosed solely by tomographic data were not considered candidates for LASIK. Patients were followed for a minimum of 12 months. Statistical analysis was performed with a Tukeys range test.

Results : 247 eyes of 164 patients were included. The mean age was 29.15 ± 5.82 years. 0 out of 154 eyes of group 1 (normal TBI) developed ectasia. 0 out of 76 eyes of group 2 (TBI=SCKC) developed ectasia. 0 out of 17 eyes of group 3 (TBI=KC) developed ectasia. A statistically significant correlation was observed between TBI, Pentacam Random Forest Index (PRFI), and Belin/Ambrosio Display-Total Deviation (BAD-D) across all groups, with higher indices noted between normal and KC groups. Corvis Biomechanical Index (CBI) lacked a linear correlation between the three groups. PTA and RSB were not statistically different between the three groups (table 2). The mean PTA was 30.32% ± 3.73, mean RSB was 364.8µ ± 31.71, mean Randleman Ectasia Risk Score was 1.05 ± 1.20 and mean maximum ablation depth was 74.29 µ ± 28.06.

Conclusions : Patients with an abnormal TBI have tomographic or biomechanical changes that deviate from the norm. This study suggests that although an increased TBI is diagnostic for keratoconus, it is not indicative of post refractive surgery ectasia, as long as the RSB>290 microns and the PTA < 40%.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.