Effect of Nictitans Gland and Third Eyelid Excisions on Ocular Surface Integrity, pH, and Tear Production in Dogs

Abstract

Prolapsed nictitans gland is a common affection in dogs. Several treatment options have been suggested such as removal of the prolapsed nictitans gland, excision of the third eyelid, or repositioning of the gland. Keratoconjunctivitis sicca (KCS) was reported to occur after excision of the prolapsed gland or the third eyelid, while recurrence is commonly associated with repositioning surgery. Therefore, the aim of this study was to investigate the effect of excisions of the nictitans gland or third eyelid on ocular surface integrity, pH, and tear production. Nictitans gland or third eyelid were excised surgically from healthy eyes in dogs. Corneal integrity, pH, and tear amount were examined for 7 months. Histological examination was performed after 7 months of surgery. Fluorescein staining was negative at the different time points in both groups. No significant change was observed in pH after excision of the third eyelid. In contrast, pH was significantly decreased after 2 weeks of removal of the nictitans gland. Tear amount was significantly declined 2 and 3 weeks after excision of the third eyelid and 3 weeks after excision of nictitans gland. The histological examination of different regions including, eyelids, cornea and conjunctiva in both groups compared to control revealed that all parts were completely normal.  However, closer to the site of the third eyelid operation severe desquamation of epithelium and infiltration of inflammatory cells were observed. In conclusion, neither excisions of the third eyelid nor the nictitans gland induce the development of KCS or affect the ocular surface integrity.