Effects of femtosecond laser-assisted minimally invasive lamellar keratoplasty (FL-MILK) on mild-to-moderate and advanced keratoconus

Purpose To compare the outcomes of femtosecond laser-assisted minimally invasive lamellar keratoplasty (FL-MILK) for mild-to-moderate keratoconus (KC) and advanced KC. Methods Prospective case series study. Sixty-three eyes of 56 patients with progressive KC underwent FL-MILK were divided into group 1 [mean keratometry (Kmean) <= 53D] and group 2 (Kmean > 53D). Best spectacle-corrected visual acuity (BSCVA), Kmean, maximum keratometry (Kmax), anterior central corneal elevation (ACE), stiffness parameter A1 (SP-A1) and deformation amplitude (DA) were evaluated preoperatively and up to 24 months postoperatively. Results Mean BSCVA improved from 0.34 +/- 0.13 logMAR preoperatively to 0.25 +/- 0.13 logMAR at 24 months postoperatively in group 1 (F = 10.10, P <.0001), and from 0.54 +/- 0.31 logMAR to 0.40 +/- 0.26 logMAR (F = 9.06, P =.0002) in group 2. Group 2 showed an average Kmax reduction of 10.9 D and an average Kmean reduction of 3.9 D at 24 months postoperatively (both P <.0001), whereas no significant change was observed in group 1. Average ACE decreased from 19.2 +/- 10.0 to 5.2 +/- 8.4 at 24 months postoperatively in group 1 (F = 28.5, P <.0001), and from 46.2 +/- 16.3 to 19.1 +/- 9.0 (F = 49.6, P <.0001) in group 2; SP-A1 increased from 53.8 +/- 12.7 mmHg/mm to 95.9 +/- 20.2 mmHg/mm in group 1 (F = 70.0, P <.0001), and from 38.6 +/- 13.4 mmHg/mm to 89.3 +/- 18.2 mmHg/mm (F = 96.9, P <.0001) in group 2; DA decreased from 1.30 +/- 0.14 mm to 1.17 +/- 0.13 mm in group 1 (F = 14.0, P <.0001), and from 1.40 +/- 0.16 mm to 1.18 +/- 0.10 mm (F = 27.6, P <.0001) in group 2. Conclusions FL-MILK can stabilize progressive KC in mild-to-moderate cases and advanced cases at 24-month follow-up. Steeper corneas are more likely to undergo flattening after FL-MILK.