Intraocular pressure in normal dairy cattle.

Intraocular pressure (IOP) was measured in normal dairy cows by applanation tonometry. In the first study of 15 Holstein and 17 Jersey cows the mean IOP by Mackay-Marg tonometry was 27.5 +/- 4.8 mmHg (range 16-39 mmHg); no significant differences (P < 0.92) were observed between the Holstein and Jersey breeds. In the second study of 15 Holstein and 12 Jersey cows, the mean IOPs by Mackay-Marg and TonoPen-XL tonometry were 28.2 +/- 4.6 mmHg (range 19-39 mmHg) and 26.9 +/- 6.7 mmHg (range 16-42 mmHg), respectively. Comparisons of the Mackay-Marg and TonoPen tonometers indicated no significant differences (P < 0.16). The mean and range of IOP in normal dairy cows within 2 SD (95% of the population) is 27 mmHg with a range of 16-36 mmHg.