Non-contact Cornea Trephination with a Flying-spot Excimer-laser System
Müller M., Sherif Z., Pleyer U., Hartmann C.
University-Department of Ophthalmology Charité Berlin
Purpose: One of the most common complications after a perforating keratoplasty is the occurrence of irregular astigmatism induced by mechanical distorsion of tissue. Non contact laser assisted trephination offers the advantage of a smooth cut. We developed a simplified method to prepare donor grafts for transplantation. Quality of the cut edges and exposure time were evaluated.
Method: The beam of an experimental excimer laser (OPTex®, Lambda Physik®) was homogenised and guided by an optical system including lenses and scanner mirrors. A special software conducts the laser beam in concentric circles over the surface of the cornea. Corneas from porcine eyes were stabilized in an artificial anterior chamber. 20 in vitro grafts were trephinated applying our method and investigated by electron microscopy.
Results: All experiments provided regular cut edges. The average exposure time was (10,5±2,7) min, the diameter of the grafts was 8.0 mm. Because the cornea of porcine eye is 1/3 thicker, exposure time for preparation of human tissue might be tolerable.
Conclusions: The experiments showed the possibility of non contact trephination with a rotating focussed excimer laser beam in a porcine cornea model. The optical alignment allows clinical use under sterile conditions because the focus lens can be integrated in a closed system.
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