Abstract
Purpose: :
To determine if the depth of a stromal pocket incision would have differential effects on the corneal nerves.
Methods: :
New Zealand white rabbits of either sex (3kg) were prepared for corneal surgery. Pockets were developed using a guarded blade so that the incision depth was set at either 150 microns or 350 microns. Eight (8) eyes of four rabbits were used in this experiment and an eye was subject to only one incision. Allocation of incisional depth between eyes was random. At the conclusion of surgery and prior to sacrifice the incisional depth was verified by OCT. At three days the animals were sacrificed and anterior segments were removed into an about one ml of PBS. Tissue was allocated at the time for either TEM or immunohisotochemistry. Antibodies for GFAP or beta tubulin were applied to alternate cryostat sections.
Results: :
The OCT results verifying the placement of the pocket showed that the more anterior pockets were between 150-200 microns and the deeper pockets were between 325-350 microns. Immunostaining with GFAP, which stains Schwann cells, showed numerous neural structures at all depths of the cornea up to the epithelium, but only outside of the volume of the pocket. Stromal lamellae over the pocket failed to show GFAP staining. Similarly for beta tubulin, which stains the intra-axonal cytoskeleton, neural structures were peripheral to the pocket and over the intact stroma some intra-epithelial nerve terminals also stained. However, the stoma and epithelium over the pocket failed to show staining. TEM of large stromal nerves peripheral to the pocket showed some edema, loss of Schwann structure and unmyelinated axons filled with mitochondria.
Keywords: cornea: basic science • innervation: neural regulation • depth