Abstract / Summary
Abstract Purpose : To evaluate the impact of early postoperative astigmatic changes on visual, refractive, and corneal outcomes following corneal allogeneic intrastromal ring segment (CAIRS) implantation for keratoconus. Methods : This retrospective observational study included patients with keratoconus who underwent CAIRS implantation at a single centre between February 2020 and October 2024. Outcomes included uncorrected and corrected distance visual acuity (UCVA, CDVA), keratometric parameters, and the absolute value of refractive cylinder (|cylinder|). Longitudinal changes were evaluated over a follow-up period of up to 36 months. Results : A total of 109 eyes were included. CAIRS implantation resulted in significant improvements in visual acuity and corneal parameters. Although the mean |cylinder| significantly decreased (from 4.07±2.56 D to 3.19±2.35 D; P<0.001), 32.4% of eyes showed an increase in |cylinder| at 1 month. Multivariate analysis revealed that prior collagen cross-linking (CXL) was associated with a higher likelihood of early increase in |cylinder| (OR=2.720, 95% CI 1.059-7.207; P=0.038), whereas higher baseline |cylinder| was associated with a lower risk (OR=0.393, 95% CI 0.221-0.651; P<0.001). Eyes with lower baseline astigmatism and prior CXL were more likely to exhibit early increase. Conclusion : CAIRS significantly improves visual and corneal parameters in keratoconus. Early increases in refractive cylinder are relatively common and are influenced by baseline astigmatism and prior CXL. These changes should be interpreted with caution, as they do not necessarily indicate unfavourable long-term outcomes.