DICLOFENAC SODIUM ATTENUATES NEURAL ACTIVITY AFTER PHOTOREFRACTIVE KERATECTOMY IN RABBITS

BACKGROUND: Photorefractive keratectomy for treating myopia has been a ssociated with severe postoperative pain, The purpose of the present s tudy was to investigate, in a rabbit model, the early effects of laser ablation on the physiology of the sensory nerves of the cornea. METHO DS: Neurophysiologic monitoring of the corneal nerves was carried out 4 to 6 hours after 5-mm diameter, circular PRK ablations with a centra l depth of 85 mu m. The effect of topical 0.1%, 0.25%, and 0.5% diclof enac sodium on the physiologic response to chemical and mechanical sti mulation was evaluated. Corneas were prepared for anatomic studies of corneal innervation. RESULTS: Heightened neural activity was observed in the corneal nerves after ablation, and exaggerated responses to sen sory stimulation with hypertonic sodium chloride solutions were record ed, Diclofenac sodium at 0.1% decreased the response to 0.5 M NaCl and 0.7 M NaCl to 67 +/- 9% and 68 +/- 7% (mean +/- standard error) of th e control response. Mechanically sensitive nerves were more resistant to diclofenac; 0.1% diclofenac had no effect, but 0.25% diclofenac red uced the response significantly (P < 0.05), Anatomic observations show ed that the ablation extended through the neural plexus. By 72 hours, long neurites tipped with growth cones had advanced into the injured r egion, indicating the initiation of neural regeneration. CONCLUSIONS: Diclofenac sodium was effective in attenuating neural activity in the cornea after excimer laser ablation. The action of this agent was show n to be different from that of a topical anesthetic, which rapidly and totally inhibited the response to all forms of stimulation.