Femtosecond laser assisted keratoplasty for keratoconus

Abstract

Purpose: To evaluate the results of treatment of keratoconus of different stages by femtosecond laser assisted procedure. Methods: Femtosecond laser (AMO Intralase 60kHz) assisted penetrating keratoplasty (FS-PKP) with “combined” trephination profile was performed for 115 eyes (main group), and traditional penetrating keratoplasty - for 112 eyes (control group) with stage 4 keratoconus. The 2 groups were compared in terms of UCVA, BSCVA, postoperative astigmatism and endothelial cell (EC) loss. An original technique of femtosecond laser-assisted deep anterior lamellar keratoplasty (FSDALK) with optimized cutting algorithm allowing to result “mushroom-shape” transplant and recipient’s bed edge and avoid using sharp instruments for making big-bubble, was performed for 34 eyes (main group), and manual deep anterior lamellar keratoplasty (DALK) – for 35 eyes (control group) with stages 2 and 3 of keratoconus. The 2 groups were compared in terms of UCVA, BSCVA, postoperative astigmatism, EC loss, central graft thickness and residual recipient’s tissue thickness. Also, corneal hysteresis (CH) and corneal resistance factor (CFR) were evaluated before and after surgery. Roughness of bared DM was measured by atomic force microscopy (AFM) comparative to the roughness of the cut, made by mechanical microkeratome (Moria II). Results: At 12 months observation after penetrating keratoplasty UCVA was 0.37±0.18 and 0.21±0.12 (p=0.023), BSCVA was 0.81±0.15 and 0.47±0.17 (p=0.01) in main and control group, respectively. Postoperative astigmatism was equal to 3.25±1.2D in main group and was higher in the control one – 4.5±1.3D (p=0.024). EC loss was equal in two groups – 18.9% (main) and 21.4% (control, p>0.05). After the lamellar procedure at 6 months observation UCVA was 0.21±0.17 and 0.12±0.13 (p=0.031), BSCVA was 0.54±0.15, and 0.42±0.14 (p=0.023) in main and control group, respectively. At 12 months UCVA was 0.29±0.19 and 0.26±0.2 (p>0.05), BSCVA was 0.66±0.15 and 0.54±0.18 (p>0.05), respectively. Part of patients, achieved BSCVA≥0.5 was 97.1% in the main group and 71.4% in the control one (p=0.013). Postoperative astigmatism was equal to 3.7±1.4 D in the main group and was higher (p=0.04) in the control one (4.8±1.9 D). EC loss (7.4 and 6.1%, p>0.05), central graft thickness (506±20 and 521±28 um, p>0.05) and residual recipient’s tissue thickness (25±4 and 25±5 um, p>0.05) were comparable. CH and CRF had improved from 6.6±1 and 4.8±1.1 mm Hg to 9.9±0.7 and 9.3±0.8 mm Hg (p<0.001) in the main group. AFM showed roughness mean square (RMS) of DM=92±6.3 nm, comparable to RMS of microkeratome-assisted cut of 120±19 nm (p>0.05). Conclusions: Introducing femtosecond laser techniques resulted in faster visual recovery, lesser postoperative astigmatism and lager part of patients, achieved BSCVA≥0.5, comparative to traditional methods. Key words: keratoconus, femtosecond laser, penetrating keratoplasty, deep anterior lamellar keratoplasty, big-bubble technique, atomic-force microscopy.