Intrastromal corneal ring segments for keratoconus: a comprehensive review of different types

This comprehensive review analyzes different types of intrastromal corneal ring segments (ICRS) used in the treatment of keratoconus, focusing on visual outcomes, complication rates, and patient selection criteria for INTACS, KeraRing, Ferrara Ring, MyoRing, and corneal allogenic intrastromal ring segments (CAIRS). We reviewed clinical studies, case reports, and long-term follow-ups to compare visual outcomes, corneal stability, and safety profiles of these ICRS types, with specific emphasis on parameters such as uncorrected distance visual acuity (UDVA), best-corrected distance visual acuity (CDVA), keratometry (Kmax reduction), and complication rates, including migration, extrusion, and postoperative visual disturbances. Each type of ICRS exhibits distinct advantages, with efficacy varying according to disease severity and corneal irregularity. INTACS demonstrated reliable visual improvements for moderate keratoconus with minimal complication rates. KeraRing provided customizable options that significantly improved UDVA and CDVA in cases with irregular astigmatism, although segment migration was more common. The Ferrara Ring was highly effective in central keratoconus, offering substantial corneal flattening with a moderate risk of visual disturbances. MyoRing effectively reduced higher-order aberrations in advanced keratoconus but was associated with a higher reoperation rate. CAIRS, combined with corneal crosslinking, showed promising outcomes with enhanced biocompatibility and minimal complications, particularly for patients sensitive to synthetic materials. ICRS types offer tailored options for keratoconus management. INTACS remains effective for moderate cases, while KeraRing and Ferrara Ring are suitable for advanced stages, especially where customization and flattening are needed. MyoRing offers significant benefits for severe ectasia, and CAIRS presents a novel, biocompatible alternative. Optimizing outcomes and minimizing complications requires tailored selection based on patient-specific corneal characteristics and disease stage. Further comparative studies are needed to refine patient selection criteria and assess the long-term efficacy of each ICRS type.