Early results of allograft intrastromal ring segment for keratoconus

This study aimed to determine the efficacy of a novel nomogram for implanting allograft intrastromal ring segments in keratoconus patients.

The study included 86 eyes of 86 patients who were followed for 6 months. Patients were treated using the Istanbul nomogram, which is used to guide the creation of corneal tunnels, utilizing a femtosecond laser, with dimensions of 4×7.5mm and a depth of 200μm. Sterile allograft corneal rings (KeraNatural™) were implanted at the precise location of the cone. Pre- and postoperative measurements of SE, CDVA, UDVA, keratometry values, and topographic map parameters were compared. Additionally, an online protractor was used to measure the angle of the cone and the angle of the implanted allograft ring.

After surgery, there was significant improvement in SE, CDVA, UCVA, keratometry values, and topographic map parameters, including anterior map elevation (AME), posterior map elevation (PME), and best-fit sphere (BFS) anterior and posterior (P<0.001). In addition, a statistically significant correlation was found between the cone angle and KeraNatural™ length (P<0.001).

Our findings highlight the importance of considering the cone angle and KeraNatural™ length in preoperative evaluations. These parameters might help predict potential visual acuity outcomes and tailor surgical plans according to individual patient needs. The stability of most visual parameters over six months reaffirms the long-term efficacy of surgical interventions. The KeraNatural™ used in this study is safe and effective in keratoconus patients and provides an opportunity to avoid keratoplasty.