Extrusion of Femtosecond Laser-Implanted Intrastromal Corneal Ring Segments in Keratoconic Eyes: Prevalence, Risk Factors, and Clinical Outcomes

Abstract

Purpose. To evaluate the prevalence, possible risk factors, and clinical results of femtosecond laser implanted intrastromal corneal ring segment (ICRS) extrusion in keratoconic eyes. Patients and Methods. This is a retrospective observational study evaluating 333 eyes of 269 patients who were subjected to femtosecond laser-implanted Keraring ICRS in the Sohag Refractive Center, Sohag, Egypt, from January 2014 to January 2019. The study included eyes with channels created by a femtosecond laser (60 kHz IntraLase femtosecond system; Advanced Medical Optics, Santa Ana, California, USA) with implantation of Keraring intrastromal corneal ring segments (Mediphacos, Belo Horizonte, Brazil). Patient data and causes of Keraring extrusions were identified as being those rings that migrated or showed melting of the cornea with no other reason which required segment removal. Results. Seven eyes were found to fit the criteria of ring extrusion (2.1%) out of the 333 eyes which had Keraring implantation. All extruded rings were from patients with keratoconus grade 3, with eccentric cones, and with femtosecond creation of the tunnel. Four eyes belonging to 3 patients (57.1%) had a history of vernal Keratoconjunctivitis, yet they did not show signs of activity at the time of implantation. They reported excessive rubbing just before they presented with conjunctival hyperemia and foreign body sensation. Five eyes (71.4%) showed chronic sun exposure. The mean minimal corneal thickness was 401.85 μm (range 384–420 μm), while the mean maximum keratometry was 61 D (range 55.18–68.96 D). Most of the extruded rings had large arcs. Six eyes had crosslinking (CXL) at the same session of the Keraring implantation. The simultaneous CXL treatment is considered as a possible significant risk factor for ring extrusion. Conclusion. ICRS is an effective reversible option for patients with keratoconus who are intolerant to hard contact lenses, yet the choice of cases and ring segments is mandatory for satisfactory results. Moreover, meticulous history taking and examination reduces the incidence of complications including extrusion.

Effects of intracorneal ring segments implementation technique and design on corneal biomechanics and keratometry in a personalized computational analysis

“…From a technical point of view, local stresses generated during implant migration could accelerate corneal weakening and cause implant extrusion. Clinically, investigated by Mounir et al 10 , the prevalence and risk factors of ICRS extrusion were performed by femtosecond laser. They found that careful evaluation and timing of the CXL can be considered as preoperative options to achieve satisfactory results.…”

“…From a mechanical point of view, the extrusion of ICRS is associated with locally induced stresses at the implant insertion site, which may be followed later by corneal melting and vascularization 10 . During postoperative implant extrusion, the cornea gradually weakens, leading to biomechanical instability and tissue failure.…”

Delayed Perforation of an Intrastromal Corneal Ring Segment into the Anterior Chamber: A Case Report and Review of the Literature

“…In contrast, the femtosecond laser method creates a tunnel at a uniform depth as measured from the corneal epithelium. Thus, when using the femtosecond laser, depth must be set at 70–80% as measured from the thinnest part of the cornea [ 22 ]. As corneal thickness is irregular in keratoconus, ICRS insertion may often be shallower than intended with the femtosecond laser.…”

A novel Q‐value‐based nomogram for single intracorneal ring segment implantation versus standard manufacturer's nomogram combined with accelerated cross‐linking for treatment of keratoconus: a randomized controlled trial

“…Out of 104 eyes receiving Keraring implantation in the current study, only one (0.96%) exhibited a postoperative complication, in the form of segment extrusion, which required surgical removal. Mounir et al ( 2020 ) reported a 2.1% Keraring‐extrusion rate in a study of 333 eyes implanted with Keraring segments using a femtosecond laser. The explanations they provided included segment migration, corneal melting and associated VKC.…”