Comparison Of Clinical And Safety Outcomes Between Manual And Femtosecond Laser-Assisted Surgery For Intrastromal Corneal Ring Segment Implantation

To compare the visual, refractive, aberrometric, and safety results of intrastromal corneal ring segments (ICRS) implantation with manual dissection and femtosecond laser-assisted surgery.

Single center, observational study which included patients with keratoconus and high astigmatism after penetrating keratoplasty (PK) who had Ferrara-type ICRS implantation using manual dissection and femtosecond laser technique (with FEMTO LDV Z8Ò, Ziemer Ophthalmic Systems AG, Bern, Switzerland) with a minimum follow-up of 6 months in the Ophthalmology Department of Local Health Unit of São João, Porto, Portugal.

LogMAR uncorrected (UDVA) and corrected (CDVA) distance visual acuity, refractive error, corneal topography (including K minimum, K maximum, K mean) and aberrometry (including the root mean square (RMS) for corneal coma-like aberration) and pachymetry map were recorded before and at 6 months after surgery. Two groups were compared according to the surgical tecnicque used for the ICRS implantation (manual group vs femtosecond laser group). The study included 9 eyes in the manual group and 13 eyes in the femtosecond laser group. Eighteen (81.8%) eyes had keratoconus and 4 (18.2%) eyes had high astigmatism after PK.

After surgery, there was a statistically significant improvement in the CDVA for the femto group (-0.27±0.31 logMAR units; p=0.016), but not for the manual group (-0.02±0.27 logMAR units; p=0.813). There was a decrease in K mean (-2.88±2.11D; <0.001 in the femto; -2.15±1.55D; p=0.006 in the manual group) and K maximum in both groups, while the K minimum, the anterior topographic astigmatism, and the coma RMS did not change significantly. No complications were reported in the femto group, while in the manual group, the postoperative complications rate was 22% (n=2), with no reported intraoperative complications. One of the patients had ICRS spontaneous extrusion and the other required ICRS exchange for visual and refractive enhancement.

Eyes that underwent femto ICRS implantation presented a significant CDVA improvement, unlike eyes that underwent manual ICRS implantation There were no significant differences between the manual and femto groups regarding keratometric outcomes. Manual dissection ICRS surgery presented a higher rate of postoperative complications (both mechanical and refractive), proving femtosecond laser as a safer surgical procedure. When available, ICRS should be performed with the femtosecond laser. If not available, manual implantation can be considered, although safety outcomes may be a concern.