Corneal biomechanical changes after intracorneal ring segment implantation in keratoconus

To evaluate by means of the Ocular Response Analyzer (ORA) the biomechanical changes that follow intracorneal ring segment (ICRS) implantation and to develop a predicting model for the postoperative visual outcome, considering these biomechanical changes and other clinical parameters.

A total of 45 consecutive keratoconic eyes of 35 patients aged 18 to 55 years and implanted with ICRS were included in this retrospective study. All patients were implanted with KeraRing using femtosecond laser technology. Visual acuity, refraction, corneal topography, and aberrations were evaluated during a 6-month follow-up. Additionally, corneal biomechanical changes were evaluated with the ORA system.

No significant changes in corneal hysteresis (CH) and corneal resistance factor (CRF) were observed at 1 month postoperatively (P ≥ 0.39). However, significant changes in these parameters were detected afterward (CH, 3 months, P = 0.03; CRF, 6 months, P = 0.02). Preoperative corneal biomechanical parameters were significantly correlated with postoperative corneal higher-order aberrations at all visits (P ≤ 0.05), although these correlations became stronger at the end of the follow-up. Multiple regression analysis revealed that corrected distance visual acuity at 1 month after surgery was significantly correlated with the preoperative mean keratometry and the preoperative difference between CH and CRF (P < 0.01, adjusted R² of 0.66).

Biomechanical parameters measured with the ORA and mean keratometry are factors allowing a prediction of the postoperative visual outcome in a short term after ICRS implantation in keratoconic eyes. In the long term, corneal biomechanical changes limit the prediction of the ring segment effect.