From synthetic to biological rings: CAIRS for visual preservation after PMMA ICRS extrusion in keratoconus, a case report.

PURPOSE: To report the outcome of partial replacement of an extruded PMMA intracorneal ring segment (ICRS) with corneal allogenic intrastromal ring segment (CAIRS) in advanced keratoconus.

CASE PRESENTATION: A patient with advanced keratoconus previously treated with a pair of Ferrara ring segments, achieved stable visual improvement for over 20 years. In 2024, extrusion of one segment occurred. The extruded PMMA segment was removed and replaced with a full-thickness CAIRS, while the second segment was left in situ. Despite technical challenges in adapting the CAIRS to the pre-existing tunnel, implantation was successful and visual acuity was preserved.

CONCLUSION

Partial exchange of an extruded ICRS with CAIRS is feasible and may maintain prior visual and biomechanical gains, offering an alternative to complete segment removal in selected cases.