Tear clearance rate in dogs: Measurement using anterior segment optical coherence tomography

Area of Science:

• Ophthalmology
• Veterinary Medicine
• Biomedical Engineering

Background:

• The tear film is crucial for maintaining ocular surface health and visual function.
• Assessing tear dynamics is important for diagnosing and managing dry eye disease.
• Anterior segment optical coherence tomography (AS-OCT) offers a non-invasive method for ocular surface evaluation.

Purpose of the Study:

• To evaluate the tear clearance rate (TCR) in dogs using AS-OCT.
• To investigate the correlation between TCR and ocular surface parameters like blink rate, Schirmer tear test-1 (STT-1), and tear film breakup time (TFBUT).
• To explore the relationship between tear meniscus height (TMH) and tear clearance in canine eyes.

Main Methods:

• AS-OCT was used to measure tear meniscus height (TMH) at various time points after saline instillation in 20 healthy dogs.
• Tear clearance rate (TCR) was calculated based on changes in TMH.
• Dogs were categorized into 'High TMHbase' and 'Low TMHbase' groups, and further into 'Satisfied' and 'Not satisfied' subgroups based on STT-1 and TFBUT values.

Main Results:

• Tear meniscus height immediately post-instillation (TMH0) was significantly higher than at 30 seconds (TMH0.5).
• A significant negative correlation was found between TCR and blink rate (p=0.02).
• Dogs in the 'Not satisfied' subgroup of the 'Low TMHbase' group exhibited a lower TCR and a higher blink rate compared to the 'Satisfied' subgroup.

Conclusions:

• Tear clearance rate (TCR) can be effectively evaluated in dogs using AS-OCT.
• A lower TCR is associated with a higher blink rate, suggesting compensatory mechanisms for tear film instability.
• Tear meniscus height (TMH) is a valuable parameter for assessing ocular surface health in dogs.