Blink patterns and kinematics of eyelid motion in ophthalmologically normal horses.

This research study explored the characteristics of blinking in healthy horses, including blink rate, types of blinks, and the dynamics of the eyelid movement during a blink. It compared these findings to human blinking behaviours and highlighted its potential use in identifying the causes of certain eye diseases in horses.

Objective and Methodology

• The study aimed to describe and quantify blinking patterns in horses that do not have any eye diseases. This information is necessary to understand normal eyelid function, which can further be useful in diagnosing eye-related pathologies.
• The research was conducted on 10 adult female horses or mares. A high-resolution videography method was used to record the blinking behaviour of these horses. The blink rate, the number of complete and incomplete blinks, and whether the blinking was unilateral (one eye) or bilateral (both eyes) were all analysed.
• To gather quantitative data, the researchers used image analysis software. This allowed them to calculate how much of the cornea was covered during a blink, how long a blink lasted, and the speed and acceleration of the eyelid during the blink.

Findings and Implications

• The results showed that the average blink rate was about 18.9 blinks per minute. Various types of blinks were identified, including minimal incomplete blinks, moderate incomplete blinks, complete blinks, and complete squeeze blinks. The latter being somewhat unique to horses comparing to humans.
• Most of the blinks were bilateral, suggesting that horses usually blink both eyes at once. The duration of a blink was approximated to be half a second. Interestingly, the speed of eyelid closure was found to be approximately twice as fast as the opening phase.
• The research discovered that the maximum velocity and acceleration values for eyelid closure were significantly higher than for opening. These kinematic values were found to be similar to those reported for humans.
• The high percentage of complete squeeze blinks observed in horses may contribute to maintaining the stability of the tear film, which is critical for ocular health. The findings of this study will enable researchers to use blinking kinematics as a potential diagnostic tool for certain corneal diseases in horses.