CAIRS and nomograms: a narrative review.

CAIRS (Corneal Allogeneic Intrastromal Ring Segments) is an emerging new treatment for keratoconus that involves implantation of allogeneic corneal tissue into the periphery of the keratoconic cornea, resulting in flattening of the cone, regularisation of the central cornea, and ultimately, improved vision. Published results have been encouraging and consequently, the procedure is gaining significant traction around the world. Several nomograms have been developed to predict visual outcomes and improve accuracy and predictability. We review and compare the results of the different nomograms (e.g. how they differ in segment preparation, sizing, and placement) and delve into the key discussion points associated with the procedure, which we hope will aid the reader in gaining a greater understanding of the procedure and allow them to plan their own CAIRS procedure, in what is a rapidly evolving field.