The retinal dystrophy reported here in Whippet dogs has a unique phenotype of an initial lack of ERG b-wave, development of retinal bullae then a progressive generalized retinal degeneration.
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) (rs = 0.39 for dogs and rs = 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.
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