Clinical outcomes after complete ring implantation in corneal ectasia using the femtosecond technology: a pilot study

Abstract

Purpose: To evaluate the clinical outcomes after implantation of the MyoRing (DIOPTEX GmBH, Linz, Austria) by means of femtosecond laser technology in eyes with corneal ectasia.

Design: Retrospective, consecutive, nonrandomized, case series.

Participants: A total of 12 eyes of 11 patients with ages ranging from 17 to 50 years were included. All cases were diagnosed with corneal ectasia according to the standard criteria: 1 case of post-LASIK ectasia and 11 cases of keratoconus. All cases presented with reduced best spectacle-corrected visual acuity, contact lens intolerance or discomfort, and central corneal thickness of more than 350 μm.

Methods: MyoRing inserts of 280 μm in thickness and 5 mm in diameter were implanted in all cases into an intrastromal corneal pocket created by means of femtosecond technology. Visual, refractive, corneal topography, and pachymetric changes were evaluated during a 6-month follow-up. In addition, corneal biomechanical changes were evaluated by means of the Ocular Response Analyzer (Reichert, Buffalo, NY).

Main outcome measures: Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction, keratometry, corneal asphericity, corneal higher-order aberrations, pachymetry, corneal hysteresis (CH), and corneal resistance factor (CRF).

Results: A significant improvement in UDVA was observed 1 week after surgery (P=0.001), which was consistent with the significant reduction in sphere (P=0.002) and cylinder (P=0.004). No significant changes were detected in these parameters afterward (P ≥ 0.263). Furthermore, a significant corneal flattening of a mean value of 8.03 diopters (D) was found (P=0.005). This keratometric change was correlated with the magnitude of corneal coma-like aberrations (r=0.830, P=0.003) and the CRF (r=-0.782, P=0.008). In regard to aberrometry, a statistically significant increase in primary spherical aberration was found 1 month after surgery (P=0.001). In addition, a significant reduction in higher-order corneal aberrations was found 3 to 6 months after surgery (P=0.027). Significant corneal thickening was also observed postoperatively in the central, nasal, and temporal areas (P ≤ 0.013). No statistically significant changes were detected (P ≥ 0.176) in corneal biomechanics. Explantation was performed in a very advanced keratoconus because of the extremely poor visual outcome.

Conclusions: MyoRing implantation using femtosecond technology in keratoconus allows successful corneal modeling, although the use of large diameters is advisable.