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[The change of tear secretion and tear film stability in castrated male rabbits].

OBJECTIVE
To evaluate the effect of androgen on tear secretion and tear film stability by observing the changes of ocular surface and tear film in the castrated male rabbit.


METHODS
Sixteen male rabbits were selected and randomly divided into the normal control group (8 rabbits) and the castrated group (8 rabbits). Schirmer's tests, tear film break-up time (BUT) and rose bangle (rb) staining were performed on the eyes of two groups at 1, 2, 3, 4 weeks, 2 and 3 months. The Chiron Diagnostics ACS: 180 Automato Chemilluminescence Systems was used to determine the two groups' testosterone level in serum at pre-castrate and post-castrate. Results were analyzed statistically. Lacrimal gland, Harder's gland, conjunctiva, cornea and limbus were removed for observation histopathologically after three months.


RESULTS
Both Schirmer's test and break-up time scores were significantly lower in the castrated group compared with the control group. The difference became more and more prominent in the course of observation. Rose bangle staining was positive in the castrated group. Testosterone level in serum was significantly lower in the post-castrate than that in the pre-cartrate. Histopathological observation showed that lacrimal glandular epithelial cells were atrophic and flat, the lumen of gland was enlarged and vesicular mucous in acinus cells disappeared. PAS positive material and conjunctival globlet cells were significantly decreased in the castrated group. Compared with the control group there were no significant morphologic changes in the corneal epithelium and limbal stem cells.


CONCLUSIONS
The low level of testosterone in castrated rabbit may contribute to the atrophy and applanation of lacrimal glandular epithelium, disappearance of vesicular mucous in acinar cells and the significant decrease of the number of conjunctival globlet cells. All these can lead to decrease of both the quantity and quality of tear secretion and thus cause the instability of tear film.