The aim of this study was to establish a new rhesus monkey model of severe dry eye.
A total of 8 rhesus monkeys were used for the study. Four monkeys had their main lacrimal gland and nictitating membrane surgically removed (group 1). Another 4 monkeys had a similar surgery with further application of 50% trichloroacetic acid on the bulbar conjunctiva (group 2). The ocular surface was evaluated before and after the surgery (1, 4, 8, 12, and 24 weeks) using Schirmer-1 test, corneal fluorescein staining, and the lissamine green test. Conjunctival impression cytology was also performed before and 24 weeks after the surgery. Finally, the cornea and the conjunctiva were evaluated using light microscopy.
A significant decrease in tear secretion was observed in all operated eyes. Schirmer test data measured were ≤4 mm in all the operated eyes. Slit-lamp examination also revealed abnormal staining in all the operated eyes that remained stable until the end of the experiment. In group 2, corneal fluorescein staining and lissamine green test values were always ≥5 (max 12) and ≥4 (max 9), respectively. Impression cytology specimens of both the treated groups showed conjunctival squamous metaplasia and a decreased number of goblet cells. Under light microscopy, the corneal epithelium appeared irregular with edematous basal epithelial cells. The conjunctiva showed a decreased goblet cell density with infiltration of inflammatory cells.
Complete removal of the principal lacrimal gland and nictitating membrane associated with the application of 50% trichloroacetic acid on the conjunctiva could induce severe dry eye in rhesus monkeys.