Outcomes of a Single-Segment Intrastromal Corneal Ring in Early Keratoconus Versus Early Pellucid Marginal Degeneration

Abstract Purpose: To determine the effect of a single-segment intrastromal corneal ring segment (ICRS;Intacs-SK) on early keratoconus (KCN) or pellucid marginal degeneration (PMD).Methods: It is a prospective interventional study. One-hundred-twenty-four eyes (99 patients) with KCN and 36 eyes (26 patients) with PMD at early stage (the maximum keratometric reading less than 55 diopters) were included to ICRS implantation using femtosecond laser at a tertiary university-based hospital and a private outpatient center. The uncorrected distance and spectacle-corrected visual acuity (UDVA and SCDVA), manifest spherical and cylindrical refractions, and keratometry indices were measured preoperatively and postoperatively, 1 week, 2 and 6 months.Results: One week after surgery, significant improvements were observed in UDVA, SCDVA, cylinder and keratometry readings of both KCN and PMD groups (all P<0.05) with no significant changes afterwards. No significant change occurred in the sphere refraction of PMD group (P=0.10) in contrast to KCN group (P<0.001). Corneal irregularity of KCN group in central 3 and 5 mm zones increased at 1 week (both P<0.001) and then continued to decrease up to 6 months. However, the corneal irregularity of PMD group had significant reduction only at 1 week in 5-mm zone (P=0.02) and 2 months in 3-mm zone (P=0.01) postoperatively. The final efficacy indexes were 1.44±0.71 and 0.87±0.40 in KCN and PMD groups, respectively. Conclusion: Visual acuity and keratometry values reached stability at 1 week, after one-segment Intacs-SK implantation in KCN and PMD groups. The short-term efficacy of the procedure was more in early KCN compared to early PMD.