Circadian rhythm of intraocular pressure in clinically normal donkeys (Equus asinus)

ABSTRACT

The present study aimed to report the circadian rhythm of intraocular pressure (IOP) in clinically normal donkeys. A prospective study was conducted on 30 adult donkeys. Measurement of the IOP was made at 2-hr interval starting at 6:00 hr till the next day at 4:00 using applanation tonometry. Measurements were recorded for both eyes and compared for male and female differences. The overall mean (± SEM) IOP measurement was 24.99 ± 0.14 mmHg. The mean (± SEM) IOP of the right and left eyes was 25.59 ± 0.19 and 24.27 ± 0.19 mmHg, respectively. The IOP values of the right and left eyes as well as of male and female values did not change significantly (P > 0.05) at all times. IOP measurements demonstrated diurnal fluctuation during the light phase of the day. The IOP significantly (P < 0.001) increased (27.07 ± 0.42) in the early morning (peak daytime at 8:00 hr) and was significantly (P < 0.001) lower (20.68 ± 0.34) at the mid-light phase (12:00 hr) compared to all evaluation times. The study documented the daily rhythm of IOP in donkeys. The 24-hr variation of IOP measurement should be considered when evaluating IOP in donkeys.

KEYWORDS:

• Intraocular pressure
• circadian
• rhythm
• eye
• donkey

Author contribution

All authors substantially contributed to the conception and design of the study, analyzed and interpreted the obtained data, drafted the article, critically revised the article for intellectual content and approved the final version of the submitted manuscript.

Declarations

The authors have declared no competing interests; none of the authors have any conflict of interest or relation with any third part that bias the publication of this report.

Disclosure statement

The authors report no conflict of interest.

Additional information

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.