Summary Comparison of the depth predictability of intracorneal ring segment implantation by mechanical versus femtosecond laser-assisted techniques using optical coherence tomography (OCT Visante®). Purpose To compare the depth predictability of intracorneal ring segment implantation by mechanical versus femtosecond laser-assisted techniques using OCT Visante®. Methods This observational prospective study included, after patients’ consent, 76 keratoconic eyes, of which 31 eyes (group 1) were operated using the mechanical technique and 45 eyes (group 2) with the femtosecond laser-assisted technique. The target depth was two-thirds of the peripheral corneal thickness, ranging from 5 to 7mm in diameter. Every patient underwent high-resolution anterior segment OCT (OCT Visante®) measurement preoperatively and for the implant depth, 1month postoperatively. Then two different sites were used to determine the segment depth, at the segment site and tangentially, at a distance of 700μm central to the segment's inner edge. Results Both measurement techniques demonstrated that targeted implantation depth of 66% of the corneal thickness was not observed in either group. The mean difference between the preoperative expected depth and final segment implantation was 76.64±48.76μm in the manual technique and 85.85±33.02μm in the femtosecond-assisted technique, with no statistically significant difference between the groups. Comparison between the measurement sites showed implantation depth to be shallower, 54.93±6.03%, at the tangential site compared to 55.14±8.08% at the implant site in group 1 and 56.17±5.82% versus 58.88±6.06%, respectively, in group 2. Conclusion Both mechanical and femtosecond laser-assisted techniques showed a more superficial Intacs® placement than predicted. No statistically significant difference was observed in implantation depth between the two groups.