Femtosecond Laser Implantation of a 355-Degree Intrastromal Corneal Ring Segment in Keratoconus: A Three-Year Follow-Up

Abstract

Purpose To evaluate the outcomes of femtosecond laser-assisted implantation of a 355-degree intracorneal ring (ICR) (Keraring) in patients with keratoconus in the three-year follow-up. Setting Future Femtolaser Center, Sohag, Egypt. Design Prospective interventional case series. Patients and Methods A prospective case series of 38 eyes of 26 patients with keratoconus had implantation of the 355-degree ICR keraring after tunnel creation with a femtosecond laser. The uncorrected visual acuities (UCVA) and best-corrected visual acuities (BCVA), sphere, cylinder, and manifest refraction spherical equivalent (SE), and mean keratometry (K), K max, and K min were evaluated preoperatively and 3, 6, 12, 24, and 36 months postoperatively, and all complications were reported. Results 38 eyes of 26 patients with mean age 25.92 ± 5.44 years were enrolled in the study, 11 were males (42.3%). The mean UCVA improved from 0.93 ± 0.21 to 0.63 ± 0.21 logMAR (P ≤ 0.001) and the mean BCVA from 0.67 ± 0.22 to 0.43 ± 0.26 logMAR (P < 0.001). The mean sphere, cylinder, and spherical equivalent have been changed dramatically from preoperative to 3 month postoperative, which is statistically significant (P ≤ 0.001), and the changes between 1 and 2 years and 2 and 3 years are also considerable and statistically significant; the K max and K min and K mean improved and the changes were statistically significant (P ≤ 0.001), and the changes between one, two, and three years were also statistically significant. The safety and efficacy indices were changed through the three-year follow-up. The complications were corneal neovascularization (36.84%), corneal melting (26.3%), and ring extrusion (31.5%) at the end of the study. Conclusions Implantation of a 355-degree intracorneal keraring using femtosecond laser improved the visual, refractive, and topographic parameters in keratoconus patients, with a high rate of ICR extrusion and instability. The study has been registered for the Pan African Clinical Trial Registry (http://www.pactr.org) database within No: PACTR201810796878908 on 29 October 2018.

Visual and Tomographic Outcomes of a 300° Arc-length ICRS Implantation in Moderate to Advanced Central Keratoconus

“…The 355° arc-length ICRS provides marked corneal flattening and a significant improvement in UDVA and CDVA. (17,18) However, a high rate of postoperative complications (ring extrusion, (17,18) corneal melting, (18) and neovascularization (18) were reported. The proximity between the ICRS tip and the incision is the main explanation for these complications.…”

“…(21)(22)(23) The newer types of ICRS with long arc-length are providing encouraging outcomes in advanced central keratoconus, suggesting that they could provide a visual restoration that avoids or at least delays corneal transplantation in this type of keratoconus when the cornea remains clear. (17,18,22,23) However, more long-term follow-up studies are required to assess the proportion of eyes in which the corneal transplantation is prevented and the percentage in which this procedure just delays the transplant. Nevertheless, if corneal transplantation were required, deep lamellar anterior keratoplasty could be safely performed after ICRS implantation and even with the ICRS in place.…”

“…(15,16) The reintroduction of the longarc ICRS models is yielding encouraging visual and refractive outcomes in more advanced keratoconus. (17)(18)(19)(20)(21)(22)(23) Nevertheless, some complications, mainly associated with the proximity of the ICRS tip to the surgical incision, have been reported. (17)(18)(19)(20) To overcome these complications, variations in long arclengths have been proposed for moderate to advanced keratoconus.…”

“…(17)(18)(19)(20)(21)(22)(23) Nevertheless, some complications, mainly associated with the proximity of the ICRS tip to the surgical incision, have been reported. (17)(18)(19)(20) To overcome these complications, variations in long arclengths have been proposed for moderate to advanced keratoconus. (21)(22)(23) It has been hypothesized that the ideal indication for this type of ICRS should be specifically for moderate to advanced central hyperpolate keratoconus.…”

Continuous Intracorneal Ring Implantation in Keratoconus: Efficacy, Predictive Factors, and Complications

“…Previous studies, however, have shown no significant differences in outcomes between femtosecond and manual dissection to create the stromal pocket. [34][35][36] Despite the success demonstrated, a significant limitation is that patients were not systematically categorized using KC grading such as the Belin-Ambrosia ABCD classification. This renders comparison with the study population more arduous.…”