The correlation between the intraocular pressure, central corneal thickness, and signalment of the horse

Abstract

The impact of central corneal thickness (CCT) on intraocular pressure (IOP) has been demonstrated in humans and various animal species but not yet in horses. The current study investigated the relationship between IOP and CCT in horses of different ages, sex, breed, and body weights using tonometry and pachymetry. Ninety-seven horses without ocular disease were examined at the Equine Clinic of the University of Veterinary Sciences Brno, Czech Republic, between 2019 and 2020. A complete ophthalmological examination was performed, including direct ophthalmoscopy and slit-lamp biomicroscopy, to include only horses with healthy eyes in the study. The central corneal thickness was measured with a pachymeter, and the IOP was measured with a tonometer. The effects of sex, age, breed, and horse weight on IOP and CCT were analysed. Measurements of IOP and CCT were acquired in all 97 horses. There was a significant correlation between CCT and age and weight in both eyes. Older and heavier individuals had high CCT values. Mares had lower IOP mean values compared to geldings and stallions. No correlation was found between IOP and CCT of the same eye. This study confirmed a relationship between individual variables such as age and weight on CCT, and sex on IOP. Based on this report, CCT should be considered a minor indicator when interpreting IOP values in healthy horses. Nevertheless, age and weight are essential constraints when interpreting CCT values and sex on IOP values in horses.