Femtosecond laser-assisted deep anterior lamellar keratoplasty in phototherapeutic keratectomy versus the big-bubble technique in keratoconus

AIM：To compare the functional and anatomic results of femtosecond laser（FSL）-assisted deep anterior lamellar keratoplasty（DALK） associated with phototherapeutic keratectomy（PTK） and FSL-assisted DALK performed using the big-bubble technique in keratoconus.METHODS：During the first phase of the study,an electron microscopy histopathology pilot study was conducted that included four unsuitable donor corneas divided into two groups：in FSL group,FSL lamellar cuts were performed on two corneas and in FSL＋PTK group,PTK was performed at the stromal beds of two corneas after FSL lamellar cuts were made.During the second phase of the study,a randomized clinical trial was conducted that included two treatment groups of patients with keratoconus：group 1（n=14 eyes） underwent FSL-assisted DALK associated with PTK and group 2（n=12 eyes） underwent FSL-assisted DALK associated with the bigbubble technique.The main outcome measures were the postoperative visual acuity（VA） and optical coherence tomography（OCT） measurements,confocal microscopic findings,and contrast sensitivity.RESULTS：In the pilot study,histopathology showed a more regular stromal bed in the FSL＋PTK group.In the clinical trial,group 1 had significantly worse best spectaclecorrected VA and contrast sensitivity（P〈0.05 for both comparisons）.The residual stromal bed measured by OCT was significantly（P〈0.05） thicker in group 1.Confocal microscopy detected opacities only at the donor-receptor interface in group 1.CONCLUSION：Patients with keratoconus treated with FSL-assisted DALK performed using the big-bubble technique fare better than treated with FSL-assisted DALK associated with PTK.