Aim To evaluate the stromal bed quality and endothelial damage after femtosecond laser (FSL) cuts into the deep corneal stroma.

Methods Using a 150-kHz FSL, a lamellar cut was aimed at a depth of 100, 300, or 500 μm in porcine corneas. Stromal bed smoothness was graded from light microscopy and scanning electron microscopy images. Rabbit corneas were cut at remaining thicknesses of 70, 100 and 150 μm using the FSL. The effects of peeling off the corneal flap and the distance between laser spots (2 or 4 μm) were examined.

Results The ratio of damaged cells in the group with a remaining depth of 70 μm was significantly larger than that in the groups with a remaining depth of 150 μm. The ratio of damaged cells in the group with a 4-μm spot separation and the flap peeled off was significantly larger than that in the group with a 4-μm spot separation and the flap not peeled off.

Conclusions Corneal endothelial damage is likely to increase when the remaining depth is less than 70 μm, and peeling off the flap damages corneal endothelial cells when the remaining depth is less than 100 μm.