# Relationship Between Intraocular Pressure and Carbonic Anhydrase Enzyme Activity in Cattle: Implications for Veterinary Ophthalmology

## TL;DR

This study found that pregnancy in cows lowers eye pressure and that a specific enzyme activity is linked to changes in eye pressure, offering new insights into cattle eye health.

## Contribution

The study establishes a novel link between carbonic anhydrase activity and intraocular pressure changes in pregnant cattle.

## Key findings

- Pregnant cows had significantly lower intraocular pressure compared to non-pregnant cows.
- Carbonic anhydrase activity correlated positively with intraocular pressure changes in both pregnant and non-pregnant cows.
- The similarity in eye pressure between left and right eyes simplifies clinical evaluation in cattle.

## Abstract

This study evaluated the relationship between intraocular pressure (IOP) and carbonic anhydrase (CA) activity in healthy pregnant and non‐pregnant Brown Swiss cows. Fourteen cows (seven pregnant, seven non‐pregnant; average age 4.5 ± 0.3 years; body weight 500 ± 50 kg) were included. After clinical and ophthalmologic examinations, IOP was measured in both eyes using a rebound tonometer on 10 consecutive mornings (9–12 AM). Blood samples were collected for the determination of plasma CA activity. Data were analysed with parametric and non‐parametric tests, and right‐left eye agreement was assessed via Bland‐Altman analysis. Pregnant cows showed significantly lower mean IOP (22.19 ± 1.43 mmHg) than non‐pregnant cows (24.50 ± 1.60 mmHg; p < 0.001), with no significant difference between the eye sides. Plasma CA activity did not differ between groups, but IOP changes correlated positively with CA level changes in pregnant (R
2 = 0.31; p < 0.001) and non‐pregnant cows (R
2 = 0.38; p = 0.001). Pregnancy significantly reduces IOP in cattle, and CA activity is associated with IOP changes, suggesting that hormonal and hemodynamic alterations during pregnancy may influence intraocular fluid dynamics. The similarity between eyes facilitates clinical evaluation. The findings may inform further studies on the role of CA in ocular physiology during pregnancy.

Schematic representation of the relationship between intraocular pressure (IOP) and carbonic anhydrase (CA) activity in pregnant and non‐pregnant cattle. Pregnancy is associated with a decrease in intraocular pressure, while plasma carbonic anhydrase activity shows a moderate positive correlation with IOP. These findings provide species‐specific insight into ocular physiology during pregnancy in cattle.