[Real-time monitoring of a femtosecond laser in Sub-Bowman Keratomileusis on human donor eyes using OCT].

PURPOSE

In LASIK (laser in situ keratomileusis) the thickness of the corneal flap is important since it is the residual corneal bed that determines corneal stability. The introduction of real-time OCT visualisation of the corneal layers during the fs-laser cut should enable the surgeon to control and monitor the position of the plane of laser-tissue-interaction during operation. To prove that optical coherence tomography (OCT) can be useful to guide femtosecond (fs)-laser in Sub-Bowman-Keratomileusis (SBK) an in-vitro experimental study was performed on human autopsy eyes in a research laboratory set-up.

METHODS

Five human autopsy eyes, unsuitable for transplantation, received fs-laser keratomileusis (flap) cuts. The laser procedure was controlled in real-time with an OCT system (Thorlabs HL AG, Lübeck, Germany) to ensure that the cut was placed just underneath Bowman's layer. As a control all eyes were dissected histologically (H & E staining) and examined under the light microscope (LM).

RESULTS

Videomonitoring of the laser process supported the feasibility of the concept to online monitor the fs-laser cutting process via OCT. A clear distinction of the corneal epithelium was possible in all eyes. Bowman's membrane was not identified in all autopsy eyes at the given resolution of the OCT used in this study. Still, LM sections confirmed that the online monitoring assured a positioning of the cutting plane at minimum distance underneath Bowman's membrane.

CONCLUSION

It was proven that real-time OCT monitoring of fs-laser SBK on human eyes is in principle possible.