Purpose: To evaluate the effect of implanting MyoRing into a femtosecond created corneal pocket on corneal asphericity in patients with keratoconus.
Methods: This prospective, non-randomized, interventional clinical study included 38 eyes with Keratoconus. Femtosecond assisted implantation of MyoRing was done for all cases. The intrastromal pocket was 7.4 mm in diameter and deep at a level equal to 80% of central corneal thickness. Corneal asphericity, curvature, thickness & elevations were evaluated 3 months after surgery.
Results: The mean age of patients at the time of surgery was 24.53±5.18 years. The same diameter of the MyoRing was used in all cases. Both UCVA and CDVA significantly improved after implantation of MyoRing, UCVA improved from 0.05 ± 0.01 to 0.31 ± 0.01 and CDVA improved from 0.29±0.14 to 0.34±0.10. The postoperative changes in all measured refractive parameters were significantly better in comparison to preoperative measures. The mean preoperative spherical equivalent of refractive error was -9.87±2.91, while the postoperative SE was -0.89±0.30. The refractive sphere and cylinder improved also from a preoperative -8.31± 2.55 and -3.11±1.93 to a postoperative values of -0.46±0.21 and -0.86±0.32 (sphere and cylinder respectively). Q value of anterior corneal surface significantly improved to a less prolate shape, from -0.49±0.11 preoperative to 0.23±0.01 postoperative. On the other hand, Q value of posterior corneal surface showed no statistical significant change after MyoRing implantation.
Conclusion: MyoRing implantation improves the anterior corneal asphericity of advanced prolate shape towards the optimal prolate Q value of -0.52 and “spherical aberration free” human corneal Q value of -0.46. This improvement in corneal asphericity may have a role in increasing postoperative visual acuity.