How low can we get? Tonometry in the Thomson gazelle (Gazella thomsoni)

Purpose: To establish a normal reference range of intraocular pressure esti mates in Thomson gazelles (Gazella thomsoni). Materials and Methods: Applanation tonometry was conducted in 22 eyes of 11 gazelles anesthetized for transportation purposes with a mixture of etorph ine hydrochloride and acepromazine maleate. Five sequential readings using a Tone-Pen XL (Mentor Ophthalmics, Inc., Norwell, MA) were obtained from ea ch eye. Results were analyzed for the effect of age, weight, gender, side, and repl icate readings and were compared with estimates in other species. Results: Mean (+/- standard deviation) intraocular pressure estimate in 22 eyes of 1 1 gazelles was 7.6 +/- 1.6 mm Hg. None of the variables tested had a signif icant effect on the results. Conclusions: To date, the intraocular pressure estimates in the Thomson gaz elle are the lowest reported in any species.