Corneal morphology in vitro after superficial keratectomy with q-switched Er:YSGG and free-running Er:YAG lasers.
OBJECTIVE
Examination of morphology in corneal ablation induced by a q-switched Er:YSGG (2.79 microm) laser and a free-running Er:YAG laser (2.94 microm).


METHODS
Defined ablation of 6-mm diameter and 15, 30, 55, 90, and 120-microm depth was performed on freshly enucleated swine eyes. Er:YSGG laser parameters: fluence 1.6 J/cm2, frequency 6 Hz, spot-size 465 microm FWHM, scanning-mode, pulse number 1520 to 6210. Er:YAG laser parameters: fluence 3 J/cm2, frequency 1.5 Hz, spotsize 6 mm, wide area ablation, pulse number 2 to 13. Corneal morphology was analyzed by gross photography, histology, scanning electron microscopy, and scanning nearfield acoustic microscopy.


RESULTS
Histology showed thermal damage of 5 to 15 microm in depth caused by the Er:YSGG laser in comparison with 10 to 20 microm by the Er:YAG laser. Average roughness of the ablated surface measured with scanning nearfield acoustic microscopy was 20 to 40 microm for the Er:YSGG laser and 5 to 15 microm for the Er:YAG laser. These data confirm the subjective impression of images created by scanning electron microscopy and gross photography.


CONCLUSIONS
Although the Er:YAG laser system appeared to demonstrate a smoother corneal surface than the q-switched Er:YSGG laser, the thermal damage in either case poses a potential limitation for clinical use in lamellar refractive surgery.
Kampmeier
J
J
Department of Ophthalmology, University Eye Hospital Ulm, Germany. juergen.kampmeier@medizin.uni-ulm.de
Russ
D
D
Schafer
S
S
Lang
G E
GE
Lasser
T
T
Steiner
R
R
Lang
G K
GK
D000818:Animals; D003315:Cornea / Q000601:surgery / Q000648:ultrastructure*; D003316:Corneal Diseases / Q000209:etiology / Q000473:pathology*; D065306:Corneal Injuries; D005131:Eye Injuries / Q000209:etiology / Q000473:pathology*; D054018:Lasers, Excimer; D008855:Microscopy, Electron, Scanning; D010781:Photography; D018903:Photorefractive Keratectomy / Q000009:adverse effects* / Q000379:methods; D013552:Swine