Long-Term Outcomes Of Intracorneal Ring Segment Implantation For The Management Of Keratoconus With Non-Coincident Topographic And Coma Axes (Duck Phenotype)

To evaluate visual and topographic long-term outcomes of the implantation of Ferrara-type intrastromal corneal ring segments (ICRS) for the refractive correction of paracentral keratoconus (KC) with non-coincident topographic and coma axis (duck phenotype).

Centro Hospitalar de Entre o Douro e Vouga (CHEDV), Santa Maria da Feira, Portugal.

This study retrospectively analyzed data from 34 eyes of 27 patients with paracentral KC with non-coincident topographic and coma axis who underwent ICRS implantation with a minimum postoperative follow-up period of 6 months. The main outcome measures were uncorrected visual acuity (UCVA), best corrected distance visual acuity (BCVA), corneal dioptric power in the flattest (K1) and steepest meridians (K2), mean corneal dioptric power (Km), asphericity (Q) and aberrometry (coma). Patients were examined before ICRS implantation (T0), as well as at 3-6 months (T1), 6-9 months (T2), 12-18 months (T3), 24-36 months (T4), 48 months (T5), and 60 months (T6) postoperatively.

ICRS implantation was performed on 34 eyes of 27 patients; 16 female. The mean age at surgery was 33.1±9.7 years. The mean follow up was 30.9± 15.0 months (range: 6–60 months). The median UCVA and BCVA improved from 0.52±0.60 and 0.22±0.24 logMAR at T0, to 0.30±0.48 and 0.05±0.16 logMAR at T4, respectively, (p<.001). The mean K1, K2 and Km showed a significant reduction of 2.08±2.30 diopters (D), 2.95±1.74 D, and 2.37±1.65 D from T0 to T1, respectively, (p<.001), and 1.81±1.99 D, 2.80±1.65 D, and 2.08±1.66 D at T4, respectively, (p<.001). The mean Q improved from -0.67±0.27 at T0 to -0.36±0.28 postoperatively at the mean follow up time (p<.001). The mean coma showed an improvement from 2.59±1.08 at baseline to 1.87±0.96 at T4 (p=.002).

Ferrara-type ICRS implantation appears to be an effective treatment option for the management of duck phenotype KC based on significant improvements in UCVA, BCVA, K1, K2, Km, Q, and coma, which are registered immediately postoperatively and sustained over a long follow-up period. These results suggest that ICRS implantation may provide long-term visual and topographic benefits for patients with paracentral KC with non-coincident topographic and coma axis.