LONG TERM RESULTS OF ALLOGRAFT CORNEAL RING SEGMENTS IMPLANTATION IN KERATOCONUS TREATMENT

To evaluate the efficacy and safety of allograft corneal ring segments implantation in the treatment of keratoconus by analysing long-term visual, refractive and tomographic results.

This prospective study included 62 eyes of 49 keratoconus patients who underwent allograft corneal ring segments (KeraNatural®; Lions VisionGift, Portland, OR, USA) implantation at Istanbul Medipol University Faculty of Medicine between February 2020 and August 2022. Patients operated with the Istanbul nomogram were evaluated preoperatively and postoperatively at 1st month, 6th month, 1st year and 3rd year. Uncorrected distance visual acuity (UDVA), best corrected distance visual acuity (CDVA), spherical equivalent (SE), spherical refraction (SR), cylindrical refraction (CR), topographic keratometric values, thinnest corneal thickness and anterior segment OCT measurements were performed.

Preoperative mean UDVA and CDVA (Snellen, decimal) were 0.18 ± 0.18 and 0.28 ± 0.20, respectively, and increased to 0.49 ± 0.29 and 0.66 ± 0.24 at the last visit (P<0.001). There was a significant decrease in SE, SR and keratometric values postoperatively (P<0.001).  There was no difference in CR and thinnest corneal thickness values (P=0.333 and 0.154, respectively). The stromal and epithelial thicknesses measured by anterior segment optical coherence tomography (OCT) were stabilised at 6th month and remained stable thereafter. No major complications or side effects were observed intraoperatively or postoperatively.

This study demonstrated that allograft corneal ring segments implantation is a safe and feasible alternative treatment for keratoconus with satisfactory visual outcomes.