A randomized controlled trial comparing femtosecond-enabled deep anterior lamellar keratoplasty and standard deep anterior lamellar keratoplasty (FEDS Study)

Abstract

Objectives: To compare outcomes of femtosecond-enabled deep anterior lamellar keratoplasty (FE-DALK) and standard deep anterior lamellar keratoplasty (S-DALK).

Methods: An open label, randomized controlled trial (Kensington Eye Institute, Toronto, ON, Canada) including 100 eyes of 97 participants with either keratoconus or corneal scarring, randomized to either FE-DALK (n = 48) or S-DALK (n = 49).

Primary outcomes: postoperative astigmatism and surgically induced corneal astigmatism (SIA) - both at 15 months.

Secondary outcomes: 6-, 12- and 15-month postoperative uncorrected- and best spectacle-corrected visual acuity, steep and flat keratometry, manifest sphere and astigmatism, rate of conversion to penetrating keratoplasty (PK), big-bubble success, central corneal thickness, endothelial cell count and complications.

Results: In intention-to-treat analysis, mean postoperative astigmatism in the FE-DALK (n = 30) and S-DALK (n = 30) groups at 15 months was 7.8 ± 4.4 D and 6.3 ± 5.0 D, respectively (p = 0.282) with an adjusted mean difference of 1.3 D (95% CI -1.08, +3.65). Mean SIA (arithmetic) was 9.2 ± 7.8 and 8.8 ± 5.4 D, respectively (p = 0.838) with a mean difference of 0.4 D (95% CI -3.13, +3.85). In an analysis of successful DALK cases only, mean postoperative astigmatism in the FE-DALK (n = 24) and S-DALK (n = 20) groups at 15 months (after excluding 4 eyes with AEs) was 7.3 ± 4.4 and 6.2 ± 4.9 D, respectively (p = 0.531) with an adjusted mean difference of 0.9 D (95% CI -1.94, +3.71). Mean SIA (arithmetic) was 9.1 ± 7.8 and 7.9 ± 4.6 D, respectively (p = 0.547) with a mean difference of 1.2 D (95% CI -2.70,+5.02). Comparison of secondary outcomes showed only weak statistical evidence.

Conclusions: In this randomized controlled trial, FE-DALK and S-DALK showed comparable functional and anatomical outcomes.

Fig. 1. Femtosecond laser settings for the creation of a full-thickness mushroom configuration in the donor cornea.

Vertical cuts overlap 10 μm horizontally and 30 μm vertically with the horizontal lamellar cut at a 90° angulation to the corneal surface to ensure completely cut intersecting wound edges. The ring lamellar cut is made at a depth of 300 μm. The posterior side-cut depth is set at 1200 μm from the epithelium (or 900 μm deep from the ring lamellar cut).

Fig. 2. Femtosecond laser settings for the creation of a partial thickness mushroom configuration in the recipient cornea.

Vertical cuts overlap 10 μm horizontally and 30 μm vertically with the horizontal lamellar cut at a 90° angulation to the corneal surface to ensure completely cut intersecting wound edges. The ring lamellar cut is made at a depth of 300 μm. The posterior side-cut depth is calculated by subtracting 100 μm of residual corneal stroma from the thinnest corneal pachymetry.

Fig. 3. CONSORT Flow Diagram.

Flow of participants through the study.