Comparison Of Morphology Of Corneal Nerve Damage And Regeneration With Upper And Nasal Corneal Flap

Objective: Excimer laser in situ keratomileusis (LASIK) maintain integrity of the corneal epithelium and Bowman, so LASIK correspond to the corneal anatomicophysiology.It has been proven that the safety, stability and predictability of LASIK are better than those of photorefractive keratectomy(PRK) and autolaminate keratectomy (ALK).Creation of corneal flap is one of the most key procedure in LASIK, which is also the most difficult part of the operation. Then the sorts and specify was the vital role of producing corneal flap. According to the model of movement, microkeratome was divided into oscillating and rotating model.In the past, back and forth horizontal microkeratome was frequently used to perform a corneal flap with nasal pedicel. Following the appliance of rotating microketatome has enabled it possible to operate the upper hinge of corneal flap. There are no systemic researches and exact conclusions comparing the two corneal flaps at different positions at present. In our study, corneal flaps were observed to compare nerve damage and regeneration of rabbits cornea in morphology.Methods: 35 adult New Zealand White rabbits were divided into 7 groups. Creations of upper hinge of corneal flap without laser photoablation were performed on one random eye and nasal hinge of corneal flap on the fellow eye. Postoperatively, 5 rabbits were killed and 10 corneas were obtained at 1 day, 3 day, 1 week, 4 week, 6 week, 10 week and 20 week. The changes on morphology of corneal nerve damage and regeneration were observed under the light microscope using histochemical gold chloride impregnation. The numbers of regeneration neurities of the two corneal flaps at third days,10weeks and 20 weeks were analyzed by t-test. P value was set on 0.05.Results: Corneal nerve damage and regeneration with upper hinge of corneal flap were similar to those with nasal hinge of corneal flap. One day after the surgery most of epithelial, subepithelia and stroma bed nerves were well preserved adjacent to the hinge of the flap. The rest of the flap, however, showed a major loss of epithelial, subepithelial and superficial stroma nerves. At the wound edge, cut stroma nerves were found in the superficial stroma. At third day , a few new regenerating thin fibers were found to emerge from the cut stroma nerve trunks at both the flap-bed interface and at the wound margins. They appeared to pass the wound margin into the flap area below the epithelium. At 10th week, an increasing number of regenerating nerve leashes were observed which were emerge from the cut stromal nerve trunks. They appeared to send anastomosing fibers among the neighboring strmmal nerves. At 20th week, the epithelial, subepithelial and anterior stromal innervation had gained an almost normal nerve density and architecture. Conclusions: There is no significant difference in morphology of corneal nerve damage and regeneration between upper and nasal hinge of corneal flap.