Abstract
INTRODUCTION: This study aimed to assess the tomographic and biomechanical progression of non-operated eyes in patients with asymmetric keratoconus who underwent unilateral intracorneal ring segment (ICRS) implantation. METHODS: This retrospective study included 33 patients (66 eyes) with asymmetric keratoconus who underwent unilateral ICRS implantation. The fellow eye did not meet clinical or tomographic criteria for surgical intervention at the time of the initial surgery. Tomographic and biomechanical data from the non-operated fellow eye were compared between baseline and the final follow-up (minimum 12 months). Scheimpflug-based corneal tomography (Pentacam(®)) assessed keratometry, curvature, corneal irregularity indices, and thickness-based metrics. Biomechanics parameters were evaluated via dynamic corneal response analysis (Corvis ST(®)). Disease progression was defined as the presence of at least two concordant changes among the following: Kmax increase > 1.0 D, thinnest corneal thickness decrease > 20 µm, BAD-D increase > 0.42, and worsening of biomechanical E-stage. RESULTS: Over a median follow-up of 31 months, non-operated fellow eyes showed no clinically meaningful changes in visual, tomographic, or biomechanical parameters, suggesting no structural progression under conservative, behavior-based management, including counseling to avoid eye rubbing, management of atopic disease, and oral riboflavin supplementation. Disease progression was observed in only two eyes (6.1%), which were subsequently referred for corneal cross-linking (CXL). ICRS-treated eyes demonstrated significant improvements in visual acuity and corneal regularity. CONCLUSION: In this paired-eye study, most non-operated fellow eyes in asymmetric keratoconus remained stable under conservative, behavior-based management combined with regular multimodal monitoring. These results support a behavior-first approach, using corneal tomography and biomechanics to detect objective progression and guide timely intervention. Conservative management in asymmetric keratoconus should be understood as an active, follow-up-dependent strategy rather than the absence of treatment. Surgical interventions should remain reserved for objectively progressing cases, recognizing that a small but clinically relevant proportion of fellow eyes still progress and require CXL.