Spectacle Wound Healing in the Royal Python (Python regius)
Twenty-five ball pythons, Python regius, were anesthetized, and 25% of the spectacle was resected. Groups of five snakes were humanely euthanized at different times from 24 h to 3 months postoperatively; the eyes were removed and fixed in either formalin or Bouin's solution, and they were sectioned through the wound for histologic evaluation. Engorgement of the spectacular vessels with edema adjacent to the wound edges was observed immediately post-operatively, with this post-surgical response subsiding over several weeks. An amorphous plaque of homogenous proteinaceous material completely filled the defect within 24 h and allowed re-establishment of the subspectacular space and normal wetting of the corneal surface within 1 wk. A variable degree of inflammatory cell infiltration occurred immediately postoperatively and subsided over 30 days. The germinal epithelium of the spectacle migrated under the amorphous plaque by 3 wk post-operatively, re-establishing a germinal center for production of new spectacle material. Normal wound healing resulted in regeneration of normal spectacle morphology by 3 months post-operatively in all animals examined. Experimental animals did not seem to be at risk for a higher incidence of ocular or subspectacular infections as a direct result of partial spectaculectomy. We conclude that partial removal of the spectacle is a feasible procedure to gain access to the ocular compartment for treatment of ophthalmic disease.ABSTRACT
Photomicrograph of a normal snake spectacle. The spectacle (S) forms a protective layer external to the cornea (C). It consists of an externally situated keratinized layer that is shed with each ecdysis and a deeper vascularized germinal layer. The subspectatcular space (SS) lies between these structures and is filled with tears.
Diagram of partial surgical resection of the spectacle of a snake. The subspectacular space is distended by injection of 2.5% methylcellulose to displace the cornea posteriorly (A), and then 25% of the spectacle is excised in a pie-shaped wedge that includes the border of the spectacular limbus from the inferior-temporal portion of the eye (B).
Photomicrographs of the histologic findings at each time period of extensive data collection. Scale is indicated by the black bar in top right corner of each image and equals 100 μm (C and E) or 200 μm (A, B, and D). (A) At 24 h, there was mild edema at the spectacle wound edges. (B) At 7 days, the exposed cornea was slightly desiccated, and spectacle edema was diffuse and more marked at the cut edges. (C) At 21 days, a proteinaceous plug completely filled the spectacular wound, and the spectacle was re-establishing under the plug. (D) At 95 days, the integrity of the spectacle is re-established, and the proteinaceous plug is shed. (E) At 111 days, the proteinaceous plug has shed, and the transparent spectacle has mild to moderate scarring at the wound edges.
Photographs of the spectacle vascular pattern. Infusion of silicone through an atrial catheter placed at euthanasia in the snake highlights changes in vasculature associated with incision and healing of the spectacle. (A) Normal vascular pattern observed in the control. At 21 days, there was evidence of neovascularization and leaking of the silicone within the proteinaceous crust (B); and at 95 days, there was an altered vascular pattern with fine arborizations within the regenerated spectacle (C).
Schematic of spectacle wound healing in the snake. The image on the right demonstrates the surgical wound immediately after resection of 25% of the spectacle. The images on the left document distinct phases in the wound healing process that can be identified histologically. One week post-wounding (top): After resection of 25% of the spectacle, a dense proteinaceous exudate develops (“crust”) adherent to the cornea in the region of the defect. This crust seals the defect and allows re-establishment of the subspectacular space (filled with tears) peripheral to the wound. Two weeks post-wounding (middle): At this time, the proteinaceous crust has organized to a greater degree and is tightly adhered to the spectacle wound edges. The crust has lifted off from the cornea, and the region under the crust is occupied by tears. The stroma (with blood vessels) and the epithelium of the spectacle have begun extending outward from the wound margin. Three weeks post-wounding (bottom): Under the proteinaceous crust, the stroma and epithelium have re-established their continuity across the wound.
