MEASURING INTRAOCULAR PRESSURE IN WHITE'S TREE FROGS (LITORIA CAERULEA) BY REBOUND TONOMETRY: COMPARING DEVICE, TIME OF DAY, AND MANUAL VERSUS CHEMICAL RESTRAINT METHODS

Ophthalmic findings and parameters in Western tiger salamanders (Ambystoma mavortium) from northern Colorado

OBJECTIVE

The aim of this study was to document ophthalmic examination findings and provide reference values for ocular examinations and diagnostics in clinically normal Western tiger salamanders (Ambystoma mavortium) and to evaluate the mydriatic effect of a topical rocuronium bromide and identify any adverse effects.

ANIMALS STUDIED

Sixteen Western tiger salamanders.

PROCEDURE

A complete ophthalmic examination, including intraocular pressure via rebound tonometry [iCare® TonoVet (dog-setting) or iCare® TonoVet Plus (dog-setting)], and fluorescein and Rose Bengal stains, was performed. Ocular surface flora culture swabs were collected for microbiology in four salamanders. Rocuronium bromide (50 μL; 0.01 mg) was administered into each eye in three salamanders. Pupil size and constriction ability were evaluated up to 60 min following administration of rocuronium bromide. Distant visual examination and Doppler heart rate were used to monitor for potential adverse effects of rocuronium bromide.

RESULTS

Observed ocular abnormalities included lipid keratopathy/keratitis (19%; 3/16), parasitic ophthalmitis (19%; 3/16), and cataracts (6.3%; 1/16). A significant difference was found between tonometry with iCare® TonoVet (11.5 ± 2.7 mmHg) versus TonoVet Plus (15.4 ± 3.7 mmHg) (p = .025). Fluorescein and Rose Bengal stains were negative in all salamanders. Ocular surface microbiology revealed a high incidence of contamination from environmental flora, with the most common isolate being unidentified as Gram-negative nonfermenters (75%; 3/4). No significant change in pupil size or constriction ability was observed with rocuronium bromide.

CONCLUSION

This is the first study to document ocular examination findings and diagnostics in captive and wild urodeles and may serve as a reference for clinical assessment and future studies of the Western tiger salamander.

Sedation and Anesthesia of Amphibians

Amphibians commonly are managed under human care for research, education, conservation, and companionship and frequently are in need of sedation, anesthesia, or end-of-life care involving euthanasia. Objective investigation of sedative and anesthetic protocols in these taxa still is in its infancy, but knowledge of current best practices is paramount to appropriate care. Tricaine methanesulfonate delivered via immersion (bath) is the most common anesthetic agent in amphibians, but several other effective techniques have been identified. This summary provides a comprehensive review of the current evidence-based literature regarding amphibian sedative, anesthetic, and euthanasia techniques.

Repeatability, reproducibility, and agreement of three tonometers for measuring intraocular pressure in rabbits

The aim of this study was to evaluate repeatability, reproducibility, and agreement of three commonly used tonometers in animal research (TonoLab, TonoVet, and TonoPEN AVIA) in a cohort of 24 rabbits. Additionally, the impact of sedation on IOP was investigated in 21 New Zealand White rabbits with the TonoVet tonometer. Repeatability was determined using the coefficient of variation (CoV) for two observers. For the TonoLab (6.55%) and TonoVet (6.38%) the CoV was lower than for the TonoPEN AVIA (10.88%). The reproducibility was highest for the TonoVet (0.2 ± 3.3 mmHg), followed by the TonoLab (0 ± 12.89 mmHg) and lowest for the TonoPEN AVIA (− 1.48 ± 10.3 mmHg). The TonoLab and TonoVet showed the highest agreement (r = 0.85, R² = 0.73). After sedation, a significant IOP reduction (often > 25%) was observed. Our results show that among the three tonometers tested, the TonoVet tonometer is best for use in rabbits while the TonoLab should be avoided. The impact of sedation on IOP was substantial and should be taken into account during experimentation.

A PRELIMINARY STUDY OF INTRINSIC AND EXTRINSIC FACTORS INFLUENCING INTRAOCULAR PRESSURE IN BROOK TROUT (SALVELINUS FONTINALIS)

Reference intervals of intraocular pressure (IOP) are poorly described in piscine species as the factors that may influence it. Rebound tonometry was used to measure IOP in 28 adult brook trout (Salvelinus fontinalis) anesthetized in a buffered solution of 60 mg/L tricaine methanesulfonate (n = 16) or restrained with electronarcosis (n = 12) at 16 mA. There was no significant effect of the eye side, sex, fish origin, and body weight, but IOP values were significantly higher with electronarcosis (mean ± SD: 16.4 ± 5.0 mm Hg) than with immersion anesthesia (10.8 ± 3.3 mm Hg; P = 0.0017). The same restraint method should be used for comparison with previously published IOP values or when evaluating individual variations over time.

OPHTHALMIC EXAMINATION FINDINGS AND INTRAOCULAR PRESSURE MEASUREMENTS IN SIX SPECIES OF ANURA

A complete ophthalmic exam, including intraocular pressure (IOP) measurement, is key to diagnosing ocular diseases such as uveitis and glaucoma in frogs. We performed complete ophthalmic anterior segment examinations and IOP rebound tonometry measurements using two different settings (other "p" and canine "d") for six anuran species. The objectives were to describe common ocular abnormalities found in these species, to compare IOP values between different tonometer settings, and to compare IOPs between species. Examinations revealed abnormalities including cataracts (11/98 total eyes), lenticular sclerosis (10/98) and lipid keratopathy (9/98). IOP was measured with the TonoVet^® and the ranges (oculus uterque, OU mm Hg other "p" setting, canine "d" setting) were giant waxy monkey tree frogs (Phyllomedusa bicolor) (3.5-7.6; 6.5-11.7; n = 5), mission golden-eyed tree frogs (Trachycephalus resinifictrix) (7.0-9.7, 13.2-15.7; n = 6), boreal toads (Bufo boreas boreas) (0.8-5.5, 5.7-10.5; n = 13), Mexican giant tree frogs (Pachymedusa dacnicolor) (3.8-5.0, 8.3-11.8; n = 3), Lake Titicaca frogs (Telmatobius culeus) (8.8-10.5, 14.0-17.2; n = 8), and mossy tree frogs (Theloderma corticale) (9.7-11.0, 15.7-17.0; n = 5). The TonoVet canine "d" setting IOP measurements were statistically higher (P = 0.01) than the other "p" setting measurements for all species except the giant waxy monkey tree frogs. IOP was significantly lower for giant waxy monkey tree frog eyes with cataracts (P < 0.05) with the other "p" setting. IOP did not statistically differ in eyes with lenticular sclerosis. IOP can be measured by rebound tonometer in anurans, but more research is needed for species-specific references using consistent settings.