Oertzenweg 19 b
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Purpose: To investigate normal intraocular pressure (IOP) values of cattle, sheep and goats
with two different tonometers (TonoVet â [TV] and TonoPen AVIA â [TPA]). Calibration of the tonometers was performed for cattle and sheep eyes. Methods: Twenty healthy cattle, sheep and goats each underwent slit-lamp biomicroscopy and IOP readings of both eyes were taken with the two different tonometers (TV in setting ‘d’). IOP results were statistically analyzed (Wilcoxon-test, P ≤ 0.05). For calibration purposes the IOP was preset from 5 to 60 mmHg in steps of 5 mmHg in 10 bovine and eight ovine freshly enucleated eyes from slaughtered animals. For every interval, readings were taken with both tonometers and compared to the manometrically controlled IOP (Mann–Whitney-U-test, P ≤ 0.05; Bland–Altman; regression analysis). Results: In cattle, sheep and goats median IOP (min–max) obtained with the TV was 23 mmHg (12–40 mmHg), 11 mmHg (7–20 mmHg) and 23 mmHg (9–37 mmHg) and with the TPA 16 mmHg (8–27 mmHg), 10 mmHg (5–18 mmHg) and 13 mmHg (4–25 mmHg), respectively. There were statistically signiﬁcant differences between the readings taken with the TV and TPA in all species (Wilcoxon-test, P ≤ 0.05). All measurements obtained with the TV and TPA within the calibration procedure differed statistically signiﬁcantly from the manometrically controlled IOP (Mann–Whitney-U-test, P ≤ 0.05). For both instruments regression formulas were calculated to correct the measurements (TV: cattle mano = (TV + 5.392)/1.226, r2 = 0.98; sheep mano = (TV + 2.5601)/0.9816, r2 = 0.98;TPA: cattle mano = (TPA + 0.7864)/0.7141, r2 = 0.92; sheep mano= (TPA + 1.1840)/0.6337, r2 = 0.98). Conclusion: In consideration of the speciﬁc regression formula both tonometers can be used effectively to assess the intraocular pressure in ruminants.