Outcomes after Implantation of KeraNatural, a Sterile Corneal Allograft Intrastromal Ring Segment (CAIRS), in Eyes with Keratoconus

Purpose To assess and describe the outcomes of corneal allograft intrastromal ring segment (CAIRS) implantation in eyes with keratoconus. Methods In this retrospective analysis, we examined the early postoperative results of CAIRS (KeraNatural) implantation after cutting a corneal tunnel with a femtosecond laser device (Ziemer Z6) in patients with keratoconus. Outcome measures included best-corrected distance visual acuity (BCDVA), spherical equivalent (SE), maximal keratometry (K max ), refractive astigmatism (RA), higher-order aberrations (HOAs), and root mean square total aberrations (total RMS), evaluated both before and a variable time after surgery, ranging from at least 30 days to 338 days, with a mean follow-up time of 141.1 +/- 79.9 days postoperatively. Results A total of 17 eyes with keratoconus of 16 patients (mean age of 36.2 +/- 17.3 years) were treated. In one eye, previous corneal UVA cross-linking (CXL) was reported in the medical history, and 9 eyes underwent adjunctive CXL at least 1 month postoperatively due to previously documented progressive disease. BCDVA (mean +/- SD) improved from preoperative values of 0.43 +/- 0.16 logMAR to 0.19 +/- 0.14 logMAR postoperatively (p < 0.001). Furthermore, the results show a significant decrease in spherical and astigmatic refraction, with the mean SE decreasing from - 2.9 +/- 4.7 D to - 0.7 +/- 3.6 D (p = 0.004). Mean RA slightly changed from - 3.42 +/- 2.18 D to - 2.51 +/- 2.31 D (p = 0.13). Additionally, mean K max significantly decreased from 57.3 +/- 5.5 D to 51.4 +/- 5.7 D (p < 0.001). In the comparison of pre- to postoperative HOA and total RMS values at 4, 5, and 6 mm, a slight tendency for improvement was found; however, these changes were not statistically significant (p > 0.05, each). Conclusion CAIRS implantation reduced corneal ectasia and improved BCDVA in patients with keratoconus. This highlights its potential as an effective visual rehabilitation strategy, particularly for patients who are intolerant to wearing contact lenses.