Comparative Study between Myoring and Ferrara Ring Intracorneal Implantation Using Femtosecond Laser for Treatment of Keratoconus

 Background: Keratoconus is a bilateral progressive, non-inflammatory ectatic corneal disease characterized by changes in corneal collagen structure and organization. Though the etiology remains unknown, novel techniques are continuously emerging for the diagnosis and management of the disease. Intracorneal rings are an effective way for treating keratoconus; the surgery is safe and has an adequate biocompatibility. The procedure is adjustable and reversible and, most importantly, effective in improving unaided visual acuity (UAVA), best corrected visual acuity (BCVA).
Aim of the Work: To compare the efficacy of MyoRing versus Ferrara ring using femtosecond laser for treatment of keratoconus as regards the visual outcome, refractive changes, keratometery reading (K-max), proper depth tilt and haze by anterior segment OCT and complications.
Patients and Methods: This study included forty eyes of patients with keratoconus. They were divided into two groups. Group (A) included twenty eyes of patients with keratoconus subjected to femtosecond laser assisted MyoRing implantation, while Group (B) included twenty eyes of patients with keratoconus subjected to femtosecond laser assisted Ferrara ring implantation.
Results: In group (A) MyoRing all patients showed improvement in UAVA, BCVA, refraction and K-max except 4 patients (20%) who showed no visual improvement despite the refractive and topographic improvement. Using the anterior segment OCT in interpretation of visual, refractive and topographic findings showed that those 4 patients had their MyoRings implanted at shallower depth with presence of intracorneal ring tilt. In group (B) Ferrara ring all patients showed improvement in UAVA, BCVA, refraction and K-max except 2 patients (10%) who showed no visual improvement despite the refractive and topographic improvement. Using the anterior segment OCT in interpretation of visual, refractive and topographic findings showed that those 2 patients had their Ferrara rings implanted at shallower depth with presence of intracorneal ring tilt.
Conclusion: In comparison between two rings, there were no differences in different parameters except that the Ferrara ring showed more improvement in BCVA and spherical component. Using the anterior segment OCT in assessment of implanted rings, helped us to explain the non-improvement in visual outcomes despite the refractive and topographic improvements.