Evaluation of the effects of age and pituitary pars intermedia dysfunction on corneal sensitivity in horses.

The research paper investigates the impact of age and pituitary pars intermedia dysfunction (PPID) on the corneal sensitivity of horses.

Study Design and Methodology

The study involved 20 adult horses which were categorised into three groups based on their age and condition status:

• PPID group: Old horses (>15 years old) diagnosed with PPID (5 horses).
• Old group: Old horses (>15 years old) without PPID (9 horses).
• Young group: Young horses (≤10 years old) without PPID (6 horses).

All horses classified as having PPID exhibited hirsutism, abnormal fat distribution, or laminitis, conditions not present in the horses of the old and young groups.

A Cochet-Bonnet aesthesiometer, a device specifically designed to measure corneal sensitivity, was used to establish the corneal touch threshold (CTT) in both eyes of each horse. The length of the nylon filament was gradually reduced from a maximum of 60mm until a consistent blink response was observed, indicating perceptible tactile sensitivity. Additionally, tear production, an important factor for eye health, was assessed using the Shirmer tear test (STT).

Research Findings

Results from the study revealed noticable differences across the groups:

• The young group showed significantly higher corneal sensitivity (47.50 ± 4.52 mm) compared to both the old (28.06 ± 5.72 mm) and PPID (21.5 ± 3.37 mm) groups.
• Old horses presented higher CTT values, indicating more sensitivity compared to horses with PPID.
• The tear production, assessed by STT, was found to be within the reference range across all groups and did not show any significant variation.

Conclusion and Implications

This research confirmed a decrease in corneal sensitivity among horses with advancing age and presence of PPID. Since reduced corneal sensitivity can result in impaired wound healing, the study suggests that aging or having PPID can increase the risk of nonhealing or recurring corneal ulcers in horses. This understanding may inform subsequent research to develop effective interventions for maintaining eye health in horses, especially among older horses or those with PPID.