Schirmer tear tests and intraocular pressures in conscious and anesthetized koalas (Phascolarctus cinereus)

INTRAOCULAR PRESSURE, TEAR PRODUCTION, AND OCULAR BIOMETRY IN HEALTHY ADULT CHEETAHS (ACINONYX JUBATUS)

Schirmer tear test (STT), intraocular pressure (IOP), and ocular biometry were measured in 58 healthy cheetahs (Acinonyx jubatus) between the ages of 2 and 14 yr in two captive groups. During routine health examination under immobilization, each animal underwent ophthalmic examination including STT, IOP, slit-lamp biomicroscopy, indirect ophthalmoscopy, and ocular ultrasonography. Mean ± SD values for STT and IOP were 13.58 ± 5.29 mm/min and 31.40 ± 5.01 mm Hg, respectively. The time between immobilization and examination significantly influenced both STT and IOP measurements. For IOP measurements, a significant group effect was also demonstrated, possibly due to the different anesthetic drug combinations used. Mean ± SD values for biometry were as follows: globe length (32.73 ± 1.74 mm), lens thickness (7.25 ± 1.09 mm), anterior chamber (8.54 ± 1.21 mm), and posterior segment (16.31 ± 2.06 mm). Surprisingly, all of the biometry measurements differed significantly between the two groups. Establishing STT, IOP, and biometric reference values is important for evaluating the ocular health status of the species. These reference values will assist veterinarians working with cheetahs to perform a full and informed ophthalmic examination.

Clinical ophthalmological diagnostic description of 10 healthy sugar gliders (Petaurus breviceps) and prevalence of ocular-related presentations in a larger hospital population

OBJECTIVE

To provide reference values for ocular examination and diagnostics in ophthalmologically normal sugar gliders (Petaurus breviceps). To retrospectively determine the prevalence of ocular diseases in sugar gliders presenting to a single institution.

ANIMALS

Ten client owned and 106 previously evaluated sugar gliders.

PROCEDURE

A descriptive study evaluated sugar gliders presented to Colorado State University's Avian, Exotics, and Zoological Medicine Service (CSU-AEZ) from August-2019 to January-2020. A complete ophthalmic examination including Schirmer tear test II (STT II), phenol red threat test (PRTT), intraocular pressure (IOP) via rebound tonometry, fluorescein, and rose bengal stain was performed under anesthesia. Conjunctival aerobic culture swabs and cytology were collected prior to ophthalmic evaluation. A retrospective review of medical records of sugar gliders presented to CSU-AEZ from 2008 to 2018 for ocular disease was performed.

RESULTS

Mean values ± standard deviation for selected diagnostics included the following: STT II: 2.2 ± 6.7 mm/min; PRTT: 0 ± 0 mm/15 s; IOP: 12 ± 2.6 mm Hg. Fluorescein and rose bengal staining highlighted corneal abrasions secondary to tear testing. The three most common conjunctival bacterial isolates cultured were Staphylococcus spp. (3/20, 15%), Coryneform spp. (3/20, 15%), and unidentified Gram-positive cocci (3/20, 15%). Retrospective analysis revealed ocular diseases to be the third most common abnormality resulting in sugar glider presentations (13/106, 12.3%).

CONCLUSION

This descriptive study gives reference values for IOP, conjunctival microbiology, and cytology for sugar gliders. STT II and PRTT provide little clinical value in sugar gliders. The retrospective study revealed that ocular abnormalities, often secondary to dental disease, are a common reason for presentation.

Field immobilization using alfaxalone and alfaxalone-medetomidine in free-ranging koalas (Phascolarctos cinereus): a randomized comparative study

OBJECTIVE

To characterize and compare two intramuscular drug protocols using alfaxalone and alfaxalone-medetomidine combination for the field immobilization of free-ranging koalas.

STUDY DESIGN

Blinded, randomized, comparative field study.

ANIMALS

A total of 66 free-ranging koalas from the Mount Lofty Ranges, South Australia.

METHODS

Koalas were randomly allocated into two groups. Group A animals were given alfaxalone alone at 3.5 mg kg^-1. Group AM animals were given alfaxalone 2 mg kg^-1 and medetomidine 40 μg kg^-1, reversed with atipamezole at 0.16 mg kg^-1. Blinded operators recorded heart rate (HR), respiratory rate (f_R), cloacal temperature, depth of sedation and times to: first effect, sedation suitable for clinical interventions, first arousal and full recovery. Data were analysed using independent t test, Mann-Whitney U test, chi-square analysis and log-rank test at 5% level of significance.

RESULTS

Suitable immobilization for clinical examination and sample collection was achieved in all animals. In groups A and AM, median time to working depth was 6.5 minutes (range: 3.4-15) and 8.1 minutes (range: 4.3-24) and time to complete recovery was 66 minutes (range: 12-138) and 34 minutes (range: 4-84), respectively, following reversal. Time to first effect was significantly shorter in group A (p = 0.013), whereas time to full arousal was significantly shorter in group AM (p = 0.007) probably due to the administration of atipamezole. Maximum HR was 117 ± 28 beats minute^-1 in group A, which was a significant increase from baseline values (p < 0.0001), whereas group AM showed a significant tachypnoea of 67 ± 25 (normal f_R 10-15; p < 0.0001).

CONCLUSIONS AND CLINICAL RELEVANCE

Both the protocols produced immobilization, enabling clinical examination and sample collection; however, protocol AM was more suitable for field work due to shorter recovery times.

Ophthalmic findings in cinereous vultures (Aegypius monachus)

OBJECTIVE

The aim of the present study was to provide ophthalmic reference values under normal physiological conditions for Aegypius monachus (cinereous vulture).

PROCEDURES

Thirty-two eyes of sixteen adult captive cinereous vultures were used for this study. Tear tests and tonometry in conscious and anesthetized states, neuro-ophthalmic tests, measurement of corneal diameter, slit-lamp biomicroscopy, ophthalmoscopy, and funduscopy were performed.

RESULTS

Schirmer tear test (STT) value was 11.4 ± 2.6 and 11.5 ± 2.8 mm/min in the right (OD) and left eye (OS), respectively. Phenol red thread test (PRT) values were 22.3 ± 2.1 mm/15 s OD and 22.8 ± 3.0 mm/15 s OS. The results showed a strong correlation between STT and PRT in both eyes. Intraocular pressure (IOP) values were 32.8 ± 6.9 mm Hg OD and 31.9 ± 7.1 mm Hg OS with TonoVet and 20.7 ± 4.5 mm Hg OD and 19.5 ± 4.1 mm Hg OS with Tono-Pen. There were significant differences in IOPs between rebound and applanation tonometry in both OD and OS. Tear production and IOP values showed significant reductions with general anesthesia in both tear tests and both tonometry (P < .001). Horizontal corneal diameter (mm) was 15.56 ± 0.96 OD and 15.56 ± 0.96 OS. Vertical diameter (mm) was 14.13 ± 0.96 OD and 14.06 ± 1.06 OS. The horizontal diameter was significantly longer than vertical diameter (P < .001).

CONCLUSIONS

Ocular morphologic information and normal reference range values for various ophthalmic measurements were obtained in clinically healthy cinereous vultures, which can facilitate accurate diagnosis and better management of ophthalmic diseases in cinereous vultures.

Measurement of tear production and intraocular pressure in conscious captive European fallow deer (DAMA dama)

Normal values for intraocular pressure (IOP) and tear production in conscious cervids have not been reported to date. Based on trends in zoological institutions to perform non-anaesthetized health exams, it is applicable to establish normal values in conscious animals, as anaesthesia and sedation can alter these parameters. The goal of this study was to estimate intraocular pressures using rebound tonometry and measure tear production values in a group of healthy, conscious, European fallow deer utilizing chute restraint. Evaluation of these values with regards to instrumentation and restraint variables will be assessed. Complete ophthalmic examinations, including estimation of IOP with rebound tonometry and measurement of tear production with Schirmer tear tests (STT) were performed on nine conscious European fallow deer (Dama dama) restrained in a chute. Correlations between IOP on the unspecified (P) and the equine (H) settings, as well as IOP and STT differences between left (OS) and right (OD) eyes were evaluated, in addition to assessment of correlations between right and left lateral recumbency on IOP and STT. Tear production measurements were 18.7 ± 5.1 mm min-1 with a 95% confidence interval (CI) range of 16.4-21.1 mm min-1 . Intraocular pressure measurements for the P setting were 16.1 ± 4.5 mmHg with a 95% CI range of 14.1-18.2 mmHg, and for the H setting were 21.5 ± 5.1 mmHg with a 95% CI range of 19.1-23.9 mmHg. No statistically significant difference (P > 0.05) was found between OS and OD in any test. Neither left nor right lateral recumbency was found to have a statistically significant effect on IOP or STT. This study represents the first assessment of ophthalmic parameters in conscious fallow deer with rebound tonometry and STT.

Intraocular pressure and Schirmer tear test values in maned wolf (Chrysocyon brachyurus)

Abstract: The purpose of this study was to establish baseline data on lacrimal quantity (STT-1) and intraocular pressure (IOP) in captive maned wolves. Ten healthy adult maned wolves were contained with a snare pole and muzzle and kept in decubitus of the left side. STT-1 measurement was performed on the lateral third of the lower conjunctival sac for one minute. The cornea was desensitized and intraocular pressure was measured with an tonopen. Average STT-1 in both eyes was 11±5mm.min-1, with no statistical difference between the left and right eye (p=0.960). Average IOP in both eyes was 20±6mmHg, with no statistical difference between the left and right eye (p=0.836). Average STT-1 was lower than, and IOP was the same as normal levels found in dogs. There was no statistical difference in the age of the animals, and STT-1 and IOP values. In the present paper, average maned wolf STT-1 levels were lower compared with those found in dogs, while the IOP was the same in maned wolves as in dogs. Due to the increased incidence in providing emergency care for maned wolf victims of road kill and fires, determination reference values of ocular parameters may improve the correct diagnosis and treatment of the disease.

Reference values and repeatability of the Schirmer tear tests I and II in domesticated, clinically normal dromedary camels (Camelus dromedarius)

OBJECTIVE

To determine the normal values and repeatability for Schirmer tear test (STT) in clinically normal dromedary camels and to analyze the influence of the age and gender on these values.

ANIMALS STUDIED

Thirty clinically normal dromedary camels of different ages (calves, immature, and mature).

PROCEDURES

Schirmer tear tests I and II were performed using commercial STT strips. Three measurements were obtained from each eye over three consecutive weeks, and the variance of these measurements was determined.

RESULTS

Mean values and coefficient of variation of STT I and STT II for the right and left eyes varied significantly among camel groups (P < 0.05). For STT I, the most frequently recorded values were >14-18, > 22-26, and >30-34 mm/min in calves, immature camels, and mature camels, respectively. For STT II, however, the most frequently recorded values were 7-14, >10-18, and >26-30 mm/min, respectively. The interassay coefficients of variation were 1.7-14.4% and were significantly lower in mature camels than in calves and immature camels (P < 0.05). Age was positively correlated with STT I (r = 0.81) and STT II values (r = 0.88). No significant variations were found between genders.

CONCLUSIONS

This preliminary study reports STT I and II values and repeatability in normal dromedary camels. This information may assist veterinary practitioners in complete ophthalmic examinations and in accurate diagnosis of ocular surface diseases affecting the tear film in this species.

Postanaesthetic tear production and ocular irritation in cats

OBJECTIVE

General anaesthesia significantly reduces tear production and normal values are not immediately re-established on ending anaesthesia. Therefore, adequate protection of the cornea has to be assured during the perianaesthetic period. There are various methods available, including taping of the eyelids and the application of eye ointments, gels and drops. In human medicine studies, different formulations were found to induce signs of ocular irritation. The aim of the present study was to determine tear production in cats after general anaesthesia, and to identify possible causes of irritation.

MATERIAL AND METHODS

Tear production was determined in 41 cats after general anaesthesia and eyes were examined for signs of irritation. Two different anaesthetic protocols were used. To protect the cornea, an ointment and gel were applied to the right and left eyes, respectively.

RESULTS

Postoperatively, tear production was significantly reduced for 6 hours and 18 hours in the right and left eyes, respectively. Two hours after anaesthesia, blepharospasm of the right eye was observed in 92.7% (n = 38) of the cats. In contrast, the left eye was always held open.

CONCLUSIONS

This study demonstrated that tear production in cats is significantly decreased both during and after anaesthesia. The degree of reduction was independent of the anaesthetic protocol. Both the eye ointment and gel proved effective in protecting the corneal surface. However, eye gel use is recommended because the eye ointment consistently caused an irritation comparable to the foreign-body sensation reported in humans.

Anterior chamber collapse syndrome in a koala

BACKGROUND

Anterior chamber collapse syndrome has been recognised in various species and is associated with early-life ocular disease or trauma. It is important to differentiate this acquired condition from a congenital malformation.

CASE REPORT

An adult female koala (Phascolarctos cinereus) was referred for assessment of buphthalmos and severe keratitis of the right eye. The degree of keratitis obstructed examination of intraocular structures. Enucleation of the affected eye was performed and the histopathological diagnosis was anterior chamber collapse syndrome and secondary glaucoma. This case contributes to the limited information available in the literature on anterior chamber collapse syndrome, a disease unique in having secondary glaucoma with minimal or no inflammation. The case also expands the literature available on ocular disease in koalas. More specifically, this is the only reported case of glaucoma, of any aetiology, in the koala.