Comparison of three methods of tonometry in horses presented for ophthalmic disease

To compare the measurement of intraocular pressure in horses with clinical ocular disease using three tonometry devices.

A total of fifty horses were presented to the New Bolton Center Ophthalmology Service.

Intraocular pressure was taken on 50 client-owned horses (100 eyes) using the TonoVet, TonoVet Plus and Tono-Pen Avia tonometers. Clinical equine patients included were presented to New Bolton Center for ophthalmic examination. Auriculopalpebral blocks were performed but horses were unsedated.

All three tonometers were found to have strong agreement among them. The strongest agreement was between the TonoVet and the TonoVet Plus with the TonoVet on average 1.330 mmHg less than the TonoVet Plus (standard deviation 4.388 mmHg). This was followed by the TonoVet and the Tono-Pen Avia Vet with the TonoVet on average 2.531 mmHg greater than the Tono-Pen Avia Vet (standard deviation 4.124 mmHg). The weakest agreement was between the TonoVet Plus and the Tono-Pen Avia with the TonoVet Plus on average 3.854 mmHg greater than the Tono-Pen Avia (standard deviation 4.724 mmHg).

All three tonometers showed strong agreement, however, the TonoVet and the TonoVet Plus carried the strongest agreement with the TonoVet Plus having slightly higher measurements overall compared with the TonoVet. Due to small variations between devices, it is recommended that the same device be used for serial measurements of intraocular pressure. However, all three devices are appropriate to use in horses presented for ophthalmic evaluation.