Evaluation of rebound tonometry in red‐eared slider turtles (Trachemys scripta elegans)

Abstract

Objective To evaluate feasibility and accuracy of intraocular pressure (IOP) measurement by rebound tonometry in adult red-eared slider turtles and determine the effects of manual and chemical restraint on IOP. Animal studied Seventeen adult red-eared slider turtles. Procedures IOP was measured with TonoLab® and TonoVet® tonometers in conscious, unrestrained turtles. To evaluate the effects of manual restraint, turtles were restrained by digital pressure on the rostral head or proximal neck. The effect of two chemical restraint protocols (dexmedetomidine, ketamine, midazolam [DKM] and dexmedetomidine, ketamine [DK] subcutaneously) on IOP was evaluated. Triplicate TonoLab® and TonoVet® readings were compared to direct manometry in 3 ex vivo turtle eyes. Results TonoLab® correlated better with manometry at IOPs <45 mm Hg than TonoVet® (linear regression slopes of 0.89 and 0.30 respectively). Mean (±SD) IOP in unrestrained conscious turtles was significantly lower (P<0.01) with TonoLab® (10.02 ± 0.66 mmHg) than with TonoVet® (11.32 ± 1.57 mmHg). Manual neck restraint caused a significant increase in IOP (+6.31 ± 5.59 mmHg), while manual rostral head restraint did not. Both chemical restraint protocols significantly reduced IOP (DKM: −1.0 ± 0.76 mmHg,; DK: −1.79 ± 1.17) compared to measurements in conscious unrestrained turtles. Conclusions Chemical and manual neck restraint affected IOP. Rostral head restraint had no significant effect on IOP and is, therefore, recommended as the appropriate restraint technique in red-eared-slider turtles. TonoLab® measurements estimated actual IOP more accurately, within physiologic range, than measurements obtained using the TonoVet®.

The eye of the red‐eared slider turtle: morphologic observations and reference values for selected ophthalmic diagnostic tests

“…Intraocular pressure in wild animals has previously been evaluated using indentation tonometry and applanation tonometry and rebound tonometry . Few studies about IOP in reptiles, especially testudine species, were reported in the literature .…”

“…Some available studies with reptile species also report normal ophthalmic parameters and selected clinical tests . Normal values for rebound tonometry and tear production have been reported for red‐eared slider turtles. The objective of this study was to report ocular morphological observations and to perform ophthalmic tests to establish a panel of normal parameters for the red‐eared turtle.…”

“…The available literature focuses on ocular diseases, pathophysiologic mechanisms and clinical treatments . Some available studies with reptile species also report normal ophthalmic parameters and selected clinical tests . Normal values for rebound tonometry and tear production have been reported for red‐eared slider turtles.…”

Ophthalmic findings in a captive population of Panamanian golden frogs: Atelopus zeteki

“…Several studies on various species have validated the use of the Tonovet through correlation with manometry, but no rebound tonometer has been validated in an anuran species. Cannizzo et al .…”

“…Several studies on various species have validated the use of the Tonovet through correlation with manometry, [18][19][20][21][22] but no rebound tonometer has been validated in an anuran species. Cannizzo et al 11 created calibration curves for both Tonovet and TonoLab in American Bullfrogs, but neither tonometer produced IOP readings that matched the manometer.…”