Contact Lens–Assisted Femtosecond Laser Harvesting of Donor Bowman Layer Grafts: A Pilot In Vitro Study With Preliminary Clinical Application in Advanced Keratoconus
Pedro Bertino, Ricardo Machado-Soares, Renata Soares Magalhães, Guilherme Andrade do Nascimento Rocha, Luciene Barbosa de Sousa, Renato AmbrósioPurpose:
To describe and evaluate a pilot technique using a sterile bandage contact lens (CL) as a spacer to overcome the minimum-depth limitations of applanation-based femtosecond laser (FSL) platforms when harvesting thin donor Bowman layer (BL) grafts, with preliminary clinical application in BL transplantation for advanced keratoconus (KC).
Methods:
This experimental and interventional case series included 9 in vitro donor corneas and 4 in vivo eyes with progressive KC. A ∼70-μm plano CL was applied to the bare donor stroma. The FSL dissection depth was programmed by adding the intended graft thickness to the CL thickness (110 μm for a ∼40-μm BL graft). Graft thickness and morphology were evaluated via optical coherence tomography (OCT). For the clinical cases, grafts were implanted into FSL-created stromal pockets; in vivo outcomes were limited to anterior segment OCT assessment of graft integration, graft thickness, and central corneal thickness over 12 months of follow-up.
Results:
The combined success rate for graft preparation was 92.3% (12/13). In vitro BL grafts yielded a median central thickness of 70 μm. The in vivo BL grafts achieved a median central thickness of 46 μm, with a median deviation of 1.5 μm from the individualized targets. Over the 12-month follow-up, anterior segment OCT showed all grafts to remain well integrated within the stromal pocket, with no displacement or interface complications.
Conclusions:
In this pilot study, the CL-assisted FSL protocol proved a reproducible method for harvesting BL grafts. By bypassing the minimum depth constraints of widely used applanation-based FSL platforms, this technique may minimize tissue loss and expand surgical access to BL transplantation for managing advanced KC, pending confirmation in larger series.