A Comparative Study on Common Scenarios of Single-segment and Double-segment Intracorneal Ring Segments in a Keratoconus Corneal Model

Keratoconus (KC) is a non-inflammatory and degenerative disease of the cornea. It is manifested by the formation of cone-shaped regions accompanying severe eyesight issues. Implantation of intrastromal corneal ring segments (ICRS)‎ is a popular treatment to improve visual acuity. Controversies exist over restoring functionality of different ICRSs. In this study, numerical models were used to quantify the mechanical and optical effects of different ICRSs on a reference cornea with central cone. Finite element (FE) simulations were used to simulate the implantation of two classes of ICRS sets common in clinical settings: a) single segment arcs of 360º (1 × 360), 350º (1 × 350), 320º (1 × 320), and b) symmetric double-segment arcs of 160º each (2 × 160), 150º each (2 × 150), 120º each (2 × 120), and 90º each (2 × 90). Results showed that implantation of symmetric double-segment arcs caused the symmetric displacement and stress distribution contours on both anterior and posterior corneal surfaces. This study shows the potential impact of a detailed mechanical analysis of ICRS placement and represents a first step toward the development of an evidence-based nomogram for the different implantation techniques and the optimization of the surgical intervention based on patient-specific modeling.