Histologic changes and wound healing response following 10-pulse noncontact holmium:YAG laser thermal keratoplasty.
BACKGROUND
Noncontact holmium:YAG laser thermal keratoplasty (Ho:YAG LTK) is a promising new technology for correction of hyperopia and astigmatism. We studied the acute histologic changes and wound healing response following Ho:YAG LTK performed with treatment parameters encompassing those used in clinical studies.


METHODS
We performed 10-pulse noncontact Ho:YAG LTK on three human corneas 1 day before their removal at penetrating keratoplasty and on six New Zealand white rabbit corneas followed for up to 3 months. Tissues were studied with light and transmission electron microscopy and immunohistochemistry.


RESULTS
The amount of acute tissue injury increased according to the pulse radiant energy. In human corneas, changes in the irradiated zones included epithelial cell injury and death, loss of fine filamentous structure in Bowman's layer, disruption of stromal lamellae, and keratocyte injury and death. In the rabbit corneas, similar acute changes were noted. By 3 weeks, epithelial hyperplasia and stromal contraction were present. Wound healing in the rabbits included repair of the epithelial attachment complex, keratocyte activation, synthesis of type I collagen, partial restoration of stromal keratan sulfate and type VI collagen, and retrocorneal membrane formation.


CONCLUSIONS
Noncontact Ho:YAG LTK produces acute epithelial and stromal tissue changes and in rabbit corneas stimulates a brisk wound healing response.
Koch
D D
DD
Cullen Eye Institute, Baylor College of Medicine, Department of Ophthalmology, Houston, Tex 77030, USA.
Kohnen
T
T
Anderson
J A
JA
Binder
P S
PS
Moore
M N
MN
Menefee
R F
RF
Valderamma
G L
GL
Berry
M J
MJ
D000818:Animals; D003094:Collagen / Q000378:metabolism; D003315:Cornea / Q000378:metabolism / Q000601:surgery / Q000648:ultrastructure*; D005500:Follow-Up Studies; D005642:Fuchs' Endothelial Dystrophy / Q000378:metabolism / Q000473:pathology* / Q000601:surgery; D006801:Humans; D007150:Immunohistochemistry; D007632:Keratan Sulfate / Q000378:metabolism; D015948:Keratoplasty, Penetrating; D053685:Laser Therapy / Q000379:methods*; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D011817:Rabbits; D014945:Wound Healing
D003094:Collagen; D007632:Keratan Sulfate