Validation of an experimental animal model for corneal additive surgery

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Purpose: To assess the hen cornea as a model for training and future wound healing studies after implantationof intrastromal corneal ring segments (ICRS) by clinical and optical outcomes.Setting: University of Valladolid, Valladolid, Spain.Design: Experimental study.Methods: One 90°, 150-μm thick polymethyl methacrylate Ferrara ICRS segment was manually implanted at70-80% depth of 192 Gallus domesticus corneas. Clinical follow-up for 6 months included monitoring cornealthickness, epithelial wound closure, edema, haze, and the location and severity of deposits. The refractive state wasalso measured. After each animal was euthanized, corneas were processed for direct transmittance and histologicalanalysis.Results: Complications were present in 16% of the eyes. Epithelial wound closure was completed at 3 ± 2 days.A slight corneal edema in the channel site was present for the first 15 days. All corneas had deposits by 4 monthslocated along the inner, outer curvatures and under the segments. Corneal haze was present only at the incisionsite. ICRS induced hyperopic changes in the refractive state without changes in direct transmitance of centralcornea. New cells and extracellular matrix were present around the segment where deposits were seen on clinicalfollow-up.Conclusions: With hen as an animal model, ICRS were implanted in a precise and reproducible way after alearning curve. Similar to humans, the follow-up period during the first 6 months after implantation showed fastwound closure, deposits, and haze at the incision site. ICRS in hens also reduced the refractive power withoutaffecting the central cornea.