Comparison of a rebound tonometer with an applanation tonometer in dogs with glaucoma

Eighteen dogs which presented to the Purdue University Ophthalmology Service with a final diagnosis of primary or secondary glaucoma, and 5 dogs with normal eye examinations, were evaluated. Each dog underwent a complete ophthalmic examination. An eye was categorised as glaucomatous if an intraocular pressure (IOP) measurement ≥25 mm Hg was obtained, and clinical signs consistent with glaucoma were present. Readings with the TonoVet were always performed first without topical anaesthesia. After obtaining readings with the TonoVet, one drop of proparacaine was applied to each eye, followed by IOP measurement with the Tono-Pen XL. As IOP increased, the difference between measurements obtained with the two tonometers was statistically significant. The TonoVet consistently gave higher IOP values compared with the Tono-Pen XL in glaucomatous eyes with Tono-Pen XL IOP readings ≥25 mm Hg. IOP readings were not significantly different between tonometers for normotensive eyes. Based on the results of the current study, the same device should be used for monitoring of IOP in individual patients.