Effects of femtosecond laser mushroom-like penetrating ring-cut on ring incision and corneal endothelial cells

Objective

To evaluate the effect of mushroom-like pattern femtosecond laser enabled penetrating keratoplasty with different laser energies on the ring incision and corneal endothelial cells, and compare with conventional penetrating keratoplasty.

Methods

According to the point/line separation and blasting energy, 48 porcine corneas were randomly divided into 6 groups by using a random number table.In group A, B, C, D and E, the point/line separation was 4/4, 4/4, 8/8, 8/8 and 4/2 μm, and the blasting energy was 1.5, 2.0, 1.5, 2.0 and 2.0 μJ; In group F, a negative pressure ring drill was used to make penetrating incisions.There were 8 porcine corneas in each group.Femtosecond laser of 200 kHz was used to make corresponding mushroom-shaped penetrating incisions on the porcine corneas, and compared with porcine corneas incisions with a ring drill.The optical and scanning electron microscope images were used to evaluate the glossiness of ring incisions.Four human corneas used femtosecond laser for mushroom-like penetrating incisions with point/line separation 8/8 μm, and blasting energy 2.0 μJ as the experimental group; three human corneas received a negative pressure ring drill for penetrating incisions as the control group.The loss rate of corneal endothelial cells was observed and compared between experimental group and control group.The donor guardians agreed to the acquisition and use of the donors’ cornea and signed informed consents.This study protocol was approved by the Ethics Committee of Nanjing First Hospital.

Results

Femtosecond laser mushroom penetrating ring incision completion rate was 100%.The corneal ring incision in each group was stepped, and sections of ring incisions in group A and group E were glossiest by the light microscope.Sections of ring incisions in group E were glossiest by the laser scanning electron microscope.The overall glossiness scores of the corneal ring incisions among various groups were statistically significantly different by the light microscopy (F=22.75, P<0.01). Among them, the glossiness scores in the group A were higher than those in the group B, and the glossiness scores in the group C were higher than those in the group D, with statistically significant differences (both P<0.05). The overall glossiness scores of corneal ring incisions among various groups were statistically significantly different by laser scanning electron microscopey (F=122.33, P<0.01). Among them, the glossiness scores in the group A were higher than those in the group B, and the the glossiness scores in the group C were higher than those in the group D, with statistically significant differences (both P<0.05). The corneal endothelial cells showed regular shape and tight arrangement in the experimental group, and irregular shape and loose connections were seen in the control group.The average corneal endothelial cell loss rate in the experimental group was (2.2±1.3)%, lower than (6.7±2.1)% of the control group, with a significant difference between them (t=3.569, P<0.05).

Conclusions

Femtosecond laser can produce perfect mushroom configuration, and the ring incision glossiness is better in comparison with trephine cutting.Femtosecond laser ring cut can lessen corneal endothelial loss.