Nictitating membrane resection in the horse: a comparison of long-term outcomes using local vs. general anaesthesia.

REASONS FOR PERFORMING STUDY: Neoplasia, for which surgical excision is a frequent treatment, is the most common disease of the equine nictitating membrane. There is little long-term follow-up information available to the practitioner regarding the long-term effects of nictitating membrane excision on ocular health. No information is available to compare recurrence of primary neoplasia of the nictitating membrane after excision with local or general anaesthesia. OBJECTIVES: To evaluate the long-term complications of nictitating membrane resection in horses; recurrence of neoplasia of the nictitating membrane when nictitating membrane resection is performed under local vs. general anaesthesia and if the method of anaesthesia used to permit resection of the affected membrane influences the recurrence of neoplasia of the nictitating membrane after complete nictitating membrane resection. METHODS: Records of 26 horses receiving resection of the nictitating membrane for primary neoplasia of the nictitating membrane 1999-2009 were reviewed. Clinical examination findings, surgical procedure, anaesthesia type, histopathological findings and details of adjunctive treatment were recorded. Owners were contacted via telephone regarding post operative outcomes. Data were analysed using a Fisher's exact test (P<0.05). RESULTS: The most common long-term complication of nictitating membrane excision was mild ocular discharge. Squamous cell carcinoma was the most frequent histopathological diagnosis. Recurrence of neoplasia was uncommon (2/26 horses). No significant difference in the number of horses experiencing recurrence of neoplasia was detected between groups receiving general anaesthesia vs. those receiving local anaesthesia. CONCLUSIONS: Resection of the nictitating membrane in horses following local anaesthesia is not associated with increased risk of recurrence of neoplasia compared with excision under general anaesthesia. Resection of the nictitating membrane is not associated with any long-term ocular side effects and can be an effective modality for cure of primary neoplasia of the nictitating membrane in selected cases.

Treatment of severe keratoconjunctivitis sicca by parotid duct transposition after tympanic neurectomy in rabbits.

PURPOSE: To investigate the feasibility of parotid duct transposition after tympanic neurectomy to treat severe keratoconjunctivitis sicca (KCS) in rabbits. METHODS: Thirty rabbits were divided into three groups in experiment 1. One eye was operated on, and the contralateral eye served as the control. In the KCS group, the lacrimal gland, harderian gland, and nictitating membrane were removed. In the group with parotid duct transposition (DT), the parotid duct was transposed into the lower conjunctival fornix. In the group with parotid duct transposition after tympanic neurectomy (DTTN), the tympanic nerve was resected in addition to parotid duct transposition. Schirmer test was performed and density of corneal staining was determined monthly after surgery, and goblet cell density was measured at postoperative month 3. In experiment 2, the tympanic nerve was resected on one side in 12 rabbits. Both sides of the parotid gland were resected for histopathology at intervals of 2 months to 1 year after surgery. RESULTS: Tear secretion from operated eyes at rest increased significantly after surgery in the treatment groups compared with the KCS group. Tear secretion from operated eyes after chewing was significantly lower in the DTTN than in the DT group. The corneal staining scores were higher in the operated than in the control eyes of the three groups, without significant difference among the operated eyes. Parotid gland atrophy on the operated side occurred at postoperative month 4 and recovered to normal 1 year after surgery. CONCLUSIONS: Parotid duct transposition after tympanic neurectomy could effectively reduce gustatory epiphora but may be insufficient to promote ocular surface health.