An Experimental Study Of Corneal Nerve Regeneration After Full-Bed Deep Lamellar Keratoplasty

Objective To observe the morphological changes of New Zealand albino rabbits corneal nerve regeneration in the grafts after Full-Bed Deep Lamellar Keratoplasty(FBDLK).Methods By means of acetylcholinesterase staining histochemical techniques, the morphological features of cholinergic nerve regeneration were monitored under light microscope in those grafts at 1month, 2months, 3months, 4months and 6months after Full-Bed Deep Lamellar Keratoplasty(FBDLK).We used a modified practical method~[6] for the assessment of the relative density of innervation. A 1X1 cm square positioned in the eyepiece of the microscope represented a sampling device. The number of nerves in the square was counted. The square was moved at different position such as superior,inferior,,nasal, temperal and central position which was 1mm from the wound margin.The mean number of the nerves was the relative density of corneal regenerated nerves.Results At 1 month following surgery, the stromal nerves in the bed extended obliquely into the grafts and then ramified further. The nerves in the grafts were finer than those in the bed .The relative density was 3/cm~2 .At 2 month following surgery, the proliferation of straight, longand fine neurites were evident in all preparations. The neurites in the central area were less than those in the peripheral area. The relative density was 11/cm .At 3 months, The second wave of regeneration which was called genuine regeneration presented, and the extensive proliferation of dense, long neurites without branching were observed. The relative density was 17/cm~2. At 4-6 months, It came to the stage of neural remodeling, the severed nerves invading directly into the grafts ,but extended short distances. The morphology of regenerated nerves were almost normal. The relative density was 7/cm2,which was only 19 percents of the normal neural relative density. Conclusion These results suggested that the regenerated corneal nerves increased gradually in the first three months after Full-Bed Deep Lamellar Keratoplasty (FBDLK). While in the last three months following operation the nerves decreased gradually, but the morphology of regenerated nerves were nearly normal. By the 6months after Full-Bed Deep Lamellar Keratoplasty (FBDLK), the relative density of corneal regenerated nerves was only 19 percents of the normal neural relative density.