Wound healing following refractive surgery in hens

Abstract

The wound-healing response is critical to the outcome of refractive surgery and studying wound healing contributes to an understanding of the pathophysiology of other corneal injuries. Animal models allow research to be conducted with sufficient samples and under controlled parameters. We studied the hen to determine the healing process from clinical, biophysical, and biological standpoints after photorefractive keratectomy (PRK). PRK (ÿ6.0 diopters) was performed in hen eyes. At 3, 6, 12, 24, 48, and 72 h and 5, 7, 15, 30, and 60 days postoperatively, we studied the clinical follow-up, objective measurements of light transmission (direct transmittance), apoptosis by TUNEL assay, proliferation by immunocytochemical analysis of 5-bromo-2 0 -deoxyuridine, and expression of alpha smooth muscle actin (SMA) in myofibroblasts in the corneas. Hen corneas reepithelialize quickly. Haze developed from 5 to 60 days after surgery and was correlated with the appearance and finalization of the expression of SMA. The direct transmittance of light was low during the first 15 days and improved at 30 and 60 days. TUNEL-positive cells were observed 3 h after surgery and the numbers decreased thereafter. Epithelial proliferation began at 12 h and was greater at 48 h, while stromal cell proliferation began at 24 h and was greater at 72 h. The hen cornea is anatomically similar to the human cornea, and the manner in which it heals is a good model for studying different surgical techniques and pharmacologic assays.

Measurement of correlation between transmission and scattering during wound healing in hen corneas

“…The different treatments and surgical techniques have been described in detail in previous works [35][36][37], although some additional details concerning the present experiment will be provided here. The corneas ranged from healthy with close to 100% transmissivity to others that were nearly fully opacified, depending on the periods after surgery and treatments.…”

“…Surgical data and methods have already been described in the literature [35,36], and here we only explain the details specific to the current experiment. Hens were anesthetized with an intramuscular injection of ketamine hydrochloride (37.5 mg kg À1 ; Ketolar, Parke-Davis S.A., Barcelona, Spain) and xylazine hydrochloride (5 mg kg À1 ; Rompun, Bayer AG, Leverkusen, Germany), followed by topical application of 0.5% tetracaine chlorhydrate and 1 mg of oxybuprocaine (Colircusı´Aneste´sico Doble, Alcon Cusı´, S.A., Barcelona, Spain).…”

Clinical and pathological effects of different acrylic intracorneal ring segments in corneal additive surgery

“…However, in this study we chose the hen as the experimental animal since, histologically, its cornea resembles human cornea in size and structure: it is thinnest centrally and it thickens toward the periphery. Furthermore, the proportions of hen cornea layer [44,45] and the fibrillar collagen arrangement [46,47] are very similar to those of human cornea. Also, in previous experiments the hen was used as animal model to study the wound-healing response after intracorneal ring segment implantation by our group, so that the learning curve was already realized [48].…”

Tissue reaction after intrastromal corneal ring implantation in an experimental animal model

“…Eleven time points after ICRS implantation or after channel preparation in control group 1 were examined histologically at 4, 12, 24, 48, and 72 hours, 7 days, and 1, 2, 3, 4 and 6 months. These times were chosen based on previous wound healing studies in hens and rabbits [17,22,23]. Enucleated eyes were fixed with 10 % buffered formalin and embedded in paraffin.…”

“…Wound healing after photorefractive keratectomy (PRK) and LASIK surgery has been described as a cascade of events, regulated by several cytokines and growth factors synthesized and released by the epithelium and lacrimal gland [23][24][25]. The quiescent keratocytes around the wound are stimulated to either undergo cell death, or alternatively, to lose the quiescent state and transition into repair or Bactivated^pheno-types.…”