Visualization of femtosecond laser pulse–induced microincisions inside crystalline lens tissue
Received 16 March 2009; received in revised form 18 June 2009; accepted 30 June 2009.
Purpose
To evaluate a new method for visualizing femtosecond laser pulse–induced microincisions inside crystalline lens tissue.
Setting
Laser Zentrum Hannover e.V., Hannover, Germany.
Method
Lenses removed from porcine eyes were modified ex vivo by femtosecond laser pulses (wavelength 1040 nm, pulse duration 306 femtoseconds, pulse energy 1.0 to 2.5 μJ, repetition rate 100 kHz) to create defined planes at which lens fibers separate. The femtosecond laser pulses were delivered by a 3-dimension (3-D) scanning unit and transmitted by focusing optics (numerical aperture 0.18) into the lens tissue. Lens fiber orientation and femtosecond laser–induced microincisions were examined using a confocal laser scanning microscope (CLSM) based on a Rostock Cornea Module attached to a Heidelberg Retina Tomograph II. Optical sections were analyzed in 3-D using Amira software (version 4.1.1).
Results
Normal lens fibers showed a parallel pattern with diameters between 3 μm and 9 μm, depending on scanning location. Microincision visualization showed different cutting effects depending on pulse energy of the femtosecond laser. The effects ranged from altered tissue-scattering properties with all fibers intact to definite fiber separation by a wide gap. Pulse energies that were too high or overlapped too tightly produced an incomplete cutting plane due to extensive microbubble generation.
Conclusions
The 3-D CLSM method permitted visualization and analysis of femtosecond laser pulse–induced microincisions inside crystalline lens tissue. Thus, 3-D CLSM may help optimize femtosecond laser–based procedures in the treatment of presbyopia.
From the Department of Ophthalmology (Stachs, Hovakimyan, Guthoff), University of Rostock, Rostock, and Laser Zentrum Hannover e.V. (Schumacher, Fromm, Heisterkamp, Lubatschowski), Hannover, Germany
Corresponding author: Oliver Stachs, PhD, Department of Ophthalmology, University of Rostock, Doberaner Straße 140, D-18057 Rostock, Germany.
No author has a financial or proprietary interest in any material or method mentioned.
Supported by BMBF FKZ 13N8709 and 13N8712 and in part by the DFG (Transregio 37, Micro- und Nanosystems in Medicine–Reconstruction of Biological Functions).
ABSTRACT