Three-Year Visual, Tomographic, and Corvis ST-Derived Biomechanical Outcomes After Combined Intrastromal Ring Implantation and Corneal Collagen Cross-Linking for Keratoconus
Combined intrastromal corneal ring segment implantation with corneal collagen cross-linking (CXL) aims to improve optical regularity and reduce the risk of ectatic progression in selected eyes with keratoconus. In this retrospective, single-center, complete-case longitudinal series, 58 eyes from 40 patients treated at OCULENS Ophthalmology Clinic between 2019 and 2022 were analyzed after same-session KeraRing implantation and conventional epithelium-off CXL, with baseline and 6-, 12-, 24-, and 36-month follow-up data. Outcomes included uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), thinnest pachymetry, maximum keratometry (Kmax), the Belin/Ambrosio enhanced ectasia total deviation index (BAD-D), the C and D components of the ABCD classification, and Corvis ST-derived dynamic deformation parameters. Longitudinal continuous outcomes were analyzed as eye-level repeated-measures estimates with Holm-adjusted paired comparisons, and stage distributions were analyzed with the Friedman test. At 36 months, UDVA improved from 0.560 ± 0.151 to 0.469 ± 0.136 logMAR and CDVA from 0.350 ± 0.109 to 0.287 ± 0.092 logMAR (both p < 0.001). Kmax decreased from 56.11 ± 3.17 D to 54.87 ± 2.86 D, BAD-D improved from 5.62 ± 1.89 to 4.70 ± 1.75, and thinnest pachymetry measured 440.7 ± 21.9 µm at 36 months, corresponding to 97.0% of baseline thickness. Corvis ST-derived deformation behavior shifted toward lower deformation amplitude and higher stiffness parameter at first applanation (SP-A1), but these device-derived parameters should be interpreted as indirect deformation response metrics rather than as direct tissue stiffness measurements. Two clinically significant complications were recorded (2/58 eyes, 3.4%): one sterile corneal infiltrate requiring ring explantation and one case of corneal melting requiring ring explantation and referral for keratoplasty. The findings support sustained 36-month visual, tomographic, and Corvis ST-derived changes after combined treatment, while interpretation remains limited by the retrospective complete-case design, unavailable denominator for cases excluded because of incomplete follow-up, eye-level analysis with bilateral cases, lack of a control group, and indirect nature of Corvis ST-derived biomechanical assessment.