Biomechanical effect of intracorneal ring segment implantation

Abstract

AbstractBackground: Previous studies have reported significant differences in corneal biomechanics between keratoconic and healthy corneas. Corvis ST® (CST – OCULUS, Wetzlar, Germany) and Ocular Response Analyser® (ORA – Reichelt Inc., Depew, NY, USA) are two single central air‐puff tonometers and are commonly used to analyse the corneal biomechanics. Implantation of intracorneal ring segments (ICRS) using a femtosecond laser represents a reliable surgical option to widen the spectrum of the stage‐related therapy of keratoconus for selected patients. Our purpose was to analyse the change in corneal biomechanical properties after ICRS implantation in keratectasia.Methods: This retrospective monocentric study included 118 patient eyes that underwent femtosecond laser‐assisted ICRS implantation (INTACS SK®, Addition Technology Inc., Des Plaines, IL, USA) for keratectasia. Biomechanical analysis was performed using both ORA, with determination of Corneal resistance factor (CRF), Corneal hysteresis (CH) and Keratoconus Match Index (KMI), as well as by CST with determination of stiffness parameter A1 (SP‐A1), Ambrosio's related thickness to the horizontal profile (Arth), integrated radius (IR), deformation amplitude‐ratio (DA‐ratio) as well as Corvis Biomechanical Index (CBI) and Tomographical Biomechanical Index (TBI). Data collection was performed preoperatively and after 6 months postoperatively for ORA and CST and additionally after 1 and 2 years for ORA.Results: The CRF decreased significantly postoperatively (5.8 ± 1.7 mmHg) compared to preoperatively (6.8 ± 3.7 mmHg; p < 0.001), and increased again during follow‐up (6.2 ± 1.9 mmHg; p = 0.001), without regaining preoperative values. CH and KMI did not change significantly. SP‐A1, IR and DA‐ratio increased significantly after ICRS implantation (p < 0.001). Arth decreased significantly from 190 ± 88 to 157 ± 108. However, there was no significant postoperative change for CBI and TBI.Conclusions: Corneal biomechanical properties showed inconsistent changes after ICRS implantation. The classical corneal biomechanical parameters (using single central air‐puff tonometers) do not seem to be suitable for follow‐up after ICRS implantation.