Intraocular pressure measurements using the TONOVET<sup>®</sup> rebound tonometer: Influence of the probe‐cornea distance
Blanche Dreher Rodrigues, Fabiano Montiani‐Ferreira, Mariza Bortolini, André Tavares Somma, András M. Komáromy, Peterson Triches Dornbusch
Abstract
Abstract Purpose To demonstrate the effect of different probe‐cornea distances during intraocular pressure (IOP) data acquisition in dogs and rats. Animals studied Twenty‐four conscious dogs and 15 anesthetized Wistar rats. Methods Three interchangeable three‐dimensional printed polylactide plastic spacer collars were used in place of the original Icare TonoVet® collar piece, which provided different distances (4, 6, and 8 mm) between the instrument's probe and the corneal surface. IOP values were obtained in sequence by a single observer, with the tonometer probe at a 4‐, 6‐, and 8‐mm distance from the corneal surface. The dogs were gently restrained, and the rats were anesthetized with isoflurane. Results Intraocular pressure values obtained at 4, 6, and 8 mm from the TonoVet® probe to corneal surface distance in both dogs and rats were significantly different ( P < .01). There was a small positive correlation between IOP (mm Hg) and probe‐cornea distance (mm) ( r s = 0.39 for dogs and r s = 0.51 for rats). In dogs, the mean IOP (± SD mm Hg) obtained at different distances were 16.2 ± 3.0 at 4 mm; 17.6 ± 3.4 at 6 mm; and 19.8 ± 3.8 at 8 mm. In rats, IOP values were 8.2 ± 1.5 at 4‐mm; 9.4 ± 1.8 at 6‐mm; and 10.5 ± 1.5 mm Hg at 8‐mm distance. Conclusions Probe‐cornea distance of the Icare TonoVet® significantly affects IOP readings, even within the 4‐ to 8‐mm range recommended by the manufacturer.