Factors predicting the visual outcome of intracorneal ring segment for keratoconus

Abstract

ABSTRACTObjectivesTo find predictive factors and to construct predictive models using epidemiological and clinical preoperative factors for the visual acuity change after intracorneal ring segment (ICRS) implantation in keratoconus patients.MethodsMedical records of 287 keratoconic eyes implanted with ICRS at Chula Refractive Surgery Centre of a tertiary university hospital (Bangkok, Thailand) between January 2012 and March 2022 were retrospectively reviewed for epidemiological and clinical preoperative variables, including those derived from Scheimpflug tomography. The correlation between these variables and postoperative uncorrected and corrected distance visual acuity change (ΔUDVA and ΔCDVA; logMAR scale) at 6 months was explored. Two hundred forty eight eyes (excluding cases with unmeasurable refraction) were randomized into 2 groups: the equation group (198 eyes) and the validation group (50 eyes). Multiple linear regression analysis was used to develop the predictive model from the equation group.ResultsTwenty preoperative variables were statistically correlated with ΔCDVA. Only the preoperative corrected distance visual acuity (CDVAp) strongly correlated with ΔCDVA (R = - 0.746). ΔUDVA correlated with only preoperative visual acuity, corneal astigmatism, and maximum Ambrósio relational thickness (ARTmax). CDVAp, spherical power (SPH), and anterior minimum sagittal curvature (Rmin) were the best predictors of ΔCDVA. The proposed model, ΔCDVA = 0.589 - 0.713×CDVAp - 0.010×SPH - 0.082×Rmin, had an acceptable predictability (R2 = 53.4%). The prediction was correct in 82% of the eyes within 0.22 logMAR.ConclusionsPotential predictive factors and models for ICRS-induced changes in visual acuity were proposed as adjunctive tools for clinicians. Such tools could be used for case selection and during counseling before ICRS implantation to maximize surgical outcomes.