A comparison of corneal cellular responses after 213-nm compared with 193-nm laser photorefractive keratectomy in rabbits.
OBJECTIVE
Corneal refractive surgery is typically performed using a 193-nm excimer laser. However, a recently developed 213-nm solid-state (5th harmonic) Nd:YAG laser presents some practical and user safety advantages, although the biological impact of using this wavelength remains poorly characterized. Here, we provide in vivo and in vitro comparisons of the corneal cellular outcomes after irradiation with 213 and 193 nm wavelengths.


METHODS
New Zealand White rabbits underwent photorefractive keratectomy with -5 diopters and a 6.5-mm optical zone and studied at time points up to 1 year. The development of haze was examined ophthalmologically and by detecting myofibroblasts immunohistochemically. Cell death was quantified using a terminal deoxynucleotidyl transferase-dUTP nick end labeling (TUNEL) assay, and the number of stromal keratocytes undergoing apoptosis estimated histologically. Superoxide dismutase activity was estimated in vitro by enzyme-linked immunosorbent assay in irradiated rabbit corneal keratocytes.


RESULTS
Our results demonstrate subtle differences in the cellular outcomes after irradiation with 213- and 193-nm lasers, despite similar degrees of corneal haze developing in both treatment groups. In vivo, the 213-nm laser results in more stable stromal cell numbers, implying a more predictable ablation outcome. In vitro, higher levels of superoxide dismutase in corneal keratocytes irradiated with 213 nm compared with 193 nm wavelengths suggest a better endogenous protection against free radicals induced by laser surgery.


CONCLUSIONS
The more favorable cellular responses after irradiation with 213 nm compared with 193 nm wavelengths are consistent with good clinical outcomes previously reported. Ablation with a 213 nm wavelength may result in better wound healing, leading to a more reliable correction of refractive errors.
Experimental and Regenerative Neurosciences, School of Animal Biology, University of Western Australia, Western Australia, Australia.
Talia
T
Sanders
Tarak
T
Pujara
Serge
S
Camelo
Ching Tat
CT
Lai
Paul
P
Van Saarloos
Lyn
L
Beazley
Jennifer
J
Rodger
D000199:Actins / Q000378:metabolism; D000818:Animals; D017209:Apoptosis; D002452:Cell Count; D002470:Cell Survival; D003315:Cornea / Q000378:metabolism / Q000473:pathology* / Q000601:surgery*; D003319:Corneal Stroma / Q000473:pathology; D004797:Enzyme-Linked Immunosorbent Assay; D005347:Fibroblasts / Q000473:pathology; D020287:In Situ Nick-End Labeling; D054018:Lasers, Excimer / Q000627:therapeutic use*; D053844:Lasers, Solid-State / Q000627:therapeutic use*; D023421:Models, Animal; D018903:Photorefractive Keratectomy / Q000379:methods*; D011817:Rabbits; D013482:Superoxide Dismutase / Q000378:metabolism; D013817:Thermography; D014945:Wound Healing
D000199:Actins; D013482:Superoxide Dismutase