The 320° Challenge: Tunnel Depth Predictability In Long-Arc Intracorneal Ring Segments — Manual Versus Femtosecond Laser

To evaluate the predictability of intrastromal tunnel depth for implantation of long-arc intracorneal ring segments (320°), comparing manual dissection and femtosecond laser-assisted techniques in patients with keratoconus.

Tertiary referral ophthalmology center.

This prospective study included 89 eyes of patients with keratoconus who underwent implantation of intracorneal ring segments with a 320° arc length. Tunnel creation was performed by manual dissection (45 eyes) or with femtosecond laser assistance (44 eyes). Planned tunnel depth was defined preoperatively as a fixed percentage of corneal thickness (80% for the manual technique and 70% for the laser-assisted technique) and was considered constant along the entire arc of the segment. Tunnel depth was assessed six months postoperatively using swept-source anterior segment optical coherence tomography, with measurements at nasal, temporal, and inferior points. Relative and absolute deltas between planned and achieved depths were calculated.

The femtosecond group demonstrated a smaller difference between planned and achieved tunnel depth, as well as lower variability of measurements, consistently across all evaluated points along the 320° intracorneal ring segment arc.

The femtosecond laser-assisted approach showed superior tunnel depth predictability, indicating enhanced surgical control and reproducibility in long-arc intracorneal ring implantation relative to manual dissection.