Limitations of erbium:YAG laser photorefractive keratectomy.
OBJECTIVE
The erbium:YAG laser (lambda = 2.94 microm) has been considered promising as an alternative to the ArF excimer laser in photorefractive keratectomy (PRK). However, corneal application of this mid-infrared solid state laser is still plagued with various disadvantages compared to that of the ArF excimer laser (lambda = 193 nm). We discuss the limitations of PRK with the erbium:YAG laser.


METHODS
Measurements of ablation threshold, ablation efficiency, and thermal damage were done to compare the process of erbium:YAG laser photoevaporization to the ArF excimer laser. PRK procedures were performed on fresh enucleated pig corneas to investigate the morphology and surface roughness of the cornea after scanning-spot and fundamental mode photoablation. Surface roughness was measured by using a tactile surface reprofiling system.


RESULTS
The ablation threshold and the ablation efficiencies for the erbium:YAG laser are significantly higher compared to the ArF excimer laser. Collateral thermal damage decreases with a reduction of laser pulse duration to a minimum of approximately 5 microm. Scanning electron microscopy and surface roughness measurements of the corneal surface after erbium:YAG laser treatment demonstrated higher surface roughness compared to ArF excimer laser treatments.


CONCLUSIONS
The erbium:YAG laser is not at present an alternative to the ArF excimer laser for photorefractive keratectomy.
Mrochen
M
M
University of Dresden, Department of Ophthalmology, Germany. mrochen@rcs.urz.tu-dresden.de
Semshichen
V
V
Funk
R H
RH
Seiler
T
T
D000818:Animals; D003315:Cornea / Q000601:surgery* / Q000648:ultrastructure; D066298:In Vitro Techniques; D053685:Laser Therapy / Q000295:instrumentation; D054018:Lasers, Excimer; D008855:Microscopy, Electron, Scanning; D018903:Photorefractive Keratectomy / Q000295:instrumentation / Q000379:methods*; D013552:Swine; D014945:Wound Healing