Corneal Allogenic Intrastromal Ring Segments (Cairs) Using Femtosecond Laser

In 2018, Jacob et al. described corneal allogenic intrastromal ring segments (CAIRS) as an alternative to synthetic materials. The corneal origin of the segments may prevent certain complications reported with PMMA arcs, including ring extrusion or migration, overlying corneal melt or acute stromal necrosis. The aim is to present a case of only eye advanced keratoconus unsuitable for synthetic intracorneal ring segment (ICRS) and intolerant to RGP contact lenses, where corneal transplantation was discarded following patient desires. For this purpose, femtosecond laser assisted CAIRS procedure was recommended as the only surgical option available to improve his vision.

Vissum (Grupo Miranza), Alicante, Spain

A 40-year-old man came for an evaluation of his left eye. He suffered a trauma of his right eye 20 years ago, that resulted in total loss of vision with no light perception and ocular phthisis. Uncorrected distant visual acuity (UDVA) of his left eye was counting fingers and the corrected distance visual acuity (CDVA) was 0,4 (decimal value). Examination revealed advanced corneal ectasia without striae or corneal scarring. The maximum thinning was pronounced at the lower periphery (358µ). The patient strictly rejected a corneal transplant on his only eye and searched for another option. One CAIRS segment was planned (160° of arc length and 400µ thick) and dissected using the Visumax 500 (Zeiss) femtosecond laser and an artificial anterior chamber. Femto dissection was achieved by two consecutive lamellar dissections after full donor epithelial removal (first plane in the thickness of 450µ with diameter of 5mm, second plane in the thickness of 400µ with diameter of 6,80 mm). Femtosecond laser was also used to create the tunnel in the recipient cornea (250µ depth and 1.1mm width with two opposite corneal incisions at the steep corneal axis).  One month postoperatively, patient’s UDVA improved to 0,6, corneal cylinder improved from -11,08D to -9,63D, and corneal coma (HOA) improved from 2,79 to 0,58µ.

This case indicates that CAIRS is a minimally invasive, safe, and effective option for treating keratoconus. Treatment of corneal ectasia with CAIRS improved visual functions, refractive and topographic parameters. The technique of preparation using femtosecond laser technology and artificial anterior chamber demonstrated precision and reproducibility and offers an alternative for corneal transplantation in advanced cases since, opposite to synthetic ICRS, there is no risk of extrusion, and the more anterior placement allows for a stronger effect as demonstrated in the current case.