The Impact of Surgical Excision of the Orbital Lacrimal Gland on the Aqueous Tear Production and Ocular Surface Health in Donkeys (Equus asinus).

This research examines the effects of surgically removing the orbital lacrimal gland (OLG) on tear production and eye health in donkeys. The results suggest significant changes to tear production and acidity, as well as potential damage to the eye’s surface, though without clear signs of dry eye condition.

Objective of the Research

• The objective of this research was to explore the role of the Orbital Lacrimal Gland (OLG) by investigating the potential effects of its surgical removal on tear production and overall health of the ocular surface. The researchers used a sample of donkeys for this experiment as this area remains less studied in equines.

Research Methodology

• The study was executed on six healthy donkeys without any ophthalmic abnormalities prior to the study. The left eye of each donkey had its OLG surgically removed, while the right eye was left as is and served as a control.
• Several tests, including external ophthalmic examination, Schirmer tear tests I and II (STT I and II for short, measuring tear production), tear pH measurement, and fluorescein staining test (detecting damage on the ocular surface) were performed on both eyes pre-surgery and post-surgery in one-week intervals for 60 days.

Results of the Research

• The conducted experiments demonstrated significant decreases in Schirmer tear test I and II values, indicating lowered tear production in the left eye where the OLG was removed.
• A rise in tear pH values was detected, suggesting increased acidity compared to the control right eye.
• Despite changes in tear production and pH, no overt clinical symptoms of keratoconjunctivitis sicca (KCS), also known as dry eye syndrome, were observed in the operated eyes.
• However, the fluorescein staining test indicated minor injury to the corneal epithelium (surface of the eye) in the operated eyes, as it revealed positive fluorescein uptake post-surgery—a sign of potential corneal dehydration.

Conclusion of the Research

• Based on the findings, the researchers concluded that surgical removal of the OLG leads to significant reduction in tear production and possible harm to the eye’s surface due to corneal dehydration, despite the absence of overt symptoms of dry eye syndrome (KCS).
• Contrary to other studies, the authors suggest that eyes subjected to OLG removal should be treated for dry eye to prevent the development of KCS post-operatively, highlighting the importance of the OLG in maintaining ocular surface health.