PURPOSE
Thin-flap keratomileusis is a procedure that
minimizes LASIK flap thickness to preserve both the corneal epithelium and the
maximum residual stroma. This study investigated the usefulness of optical
coherence tomography (OCT) as a tool in guiding the femtosecond laser in the
creation of a thin flap in human eyes in a non-randomized case series.
METHODS
In a private research laboratory, an in vitro
investigation was performed on human autopsy eyes. Five human cadaver eyes,
unsuitable for transplantation, underwent flap creation with a femtosecond
laser. The laser procedure was controlled in real-time with an OCT system
(Thorlabs HL AG) to ensure that the cut was placed just underneath
Bowman’s layer. The repetition rate of the femtosecond laser was 10 MHz
with a single-pulse duration of <400 femtoseconds (pulse energy in the nJ
range). As a control, all eyes underwent histological dissection and were
examined using light microscopy.
RESULTS
Video monitoring of the flap creation supported the
feasibility of real-time OCT monitoring of the femtosecond laser flap creation
process. A clear distinction of the corneal epithelium was possible in all
eyes. Bowman’s layer was not identified in all donor eyes at the given
resolution of the OCT device used in this study. Light microscopy demonstrated
flaps approximately 50-µm thick, confirming that the real-time monitoring
assured a positioning of the cutting plane at minimum distance underneath
Bowman’s layer.
CONCLUSIONS
This study of five human cadaver eyes shows
that real-time OCT monitoring of the creation of thin-flaps in LASIK using a
femtosecond laser is possible, thus ensuring that the flap is created at the
desired depth. [J Refract Surg. 2010;26:57-60.]
doi:10.3928/1081597X-20101215-09
AUTHORS
From Augenklinik am Neumarkt, Cologne (Kermani, Oberheide);
Rowiak GmbH, Hannover (Will); and Laser Zentrum Hannover e.V., Hannover
(Massow, Lubatschowski), Germany.
The authors have no proprietary interest in the materials
presented herein.
This paper was presented at the Lens, Refractive &
Wavefront Summit ARI/WFC 2009; March 5-7, 2009; Alicante, Spain.
Correspondence: Omid Kermani, MD, Augenklinik am Neumarkt,
Schildergasse 107-109, 50667 Cologne , Germany. Tel: 49 221 65072271; Fax: 49
221 65072279; E-mail: o.kermani@augenportal.de
