Evaluation of intraocular pressure in conscious ferrets (Mustela putorius furo ) by means of rebound tonometry and comparison with applanation tonometry

Visual cortex damage in a ferret model of ocular hypertension

PURPOSE

We aimed to analyze the changes in the visual cortex of a ferret model of ocular hypertension (OH) using cytochrome oxidase (CO) staining.

STUDY DESIGN

Experimental.

METHODS

OH was induced in 9 ferrets by means of injection of cultured conjunctival cells into the anterior chamber of the right eye. Three ferrets were used as the controls. CO staining was performed to assess the metabolic intensity at the II-III and IVC layers of the visual cortex.

RESULTS

The intensities of CO staining in the right and left II-III layers of the primary visual cortex (V1) in the OH ferrets were 39.8 ± 10.3 and 41.9 ± 9.2 arbitrary units, respectively. In the control ferrets, the intensity was 88.1 ± 8.1 arbitrary units. The intensity of CO staining of the II-III layers obtained from the OH eyes was significantly lower than that from the control eyes (unpaired t test, P < .01). The intensities of CO staining in the right and left IVC layers of V1 in the OH ferrets were 60.3 ± 12.8 and 60.0 ± 13.5 arbitrary units, respectively. In the control ferrets, the intensity was 111.4 ± 9.6 arbitrary units. The CO staining intensity of the IVC layer obtained from the OH eyes was significantly lower than that from the control eyes (unpaired t test, P < .01).

CONCLUSION

The CO staining intensity was reduced in the visual cortex from OH eyes. This study revealed that OH causes metabolic change in the visual cortex.

Ocular examination findings and measurements of tear production and tonometry of ring-tailed coatis (nasua nasua)

OBJECTIVE

To describe ocular anatomical features and to determine tear production and tonometry in normal anesthetized ring-tailed coati (Nasua nasua).

ANIMALS

Eight male and seven female ring-tailed coatis (30 eyes) were evaluated, with ages ranging from 7 months to 10 years old.

PROCEDURES

The animals were anesthetized with isoflurane and had STT 1, rebound and applanation tonometry, and palpebral fissure length (PFL) measured in both eyes. Rebound tonometry was measured with both TonoVet® and TonoVet Plus®. All eyes were evaluated with slit-lamp biomicroscopy. Following pharmacological mydriasis, direct fundoscopy was performed. ANOVA and Tukey tests were used for the data analysis.

RESULTS

There were upper and lower eyelids, as well as a third eyelid. Eyelashes were present on the upper eyelid, while meibomian glands openings were visible on both. The bulbar conjunctiva was pigmented. The pupil was obliquely horizontally ovoid and teardrop shaped when miotic. The color of the iris and tapetum lucidum varied with age. The optic disk was round, and the retina was holangiotic. The mean ± standard deviation values obtained were as follows: STT: 2.50 ± 2.39 mm/min; rebound tonometry: 9.50 ± 2.43 mmHg (TonoVet®, calibration P), 14.60 ± 2.82 mmHg (TonoVet®, calibration D), 18.93 ± 3.99 mmHg (TonoVet Plus®, calibration dog); applanation tonometry: 18.66 ± 4.16 mmHg; PFL: 10.98 ± 1.67 mm.

CONCLUSIONS AND CLINICAL RELEVANCE

Anatomical and clinical ophthalmic data presented in this study are unprecedented for this species. The results can be used as clinical reference parameters, allowing for better care of these species. The lack of data for the Procyonidae family must be regarded as an incentive for more studies.

Structural Changes and Astrocyte Response of the Lateral Geniculate Nucleus in a Ferret Model of Ocular Hypertension

We investigated structural changes and astrocyte responses of the lateral geniculate nucleus (LGN) in a ferret model of ocular hypertension (OH). In 10 ferrets, OH was induced via the injection of cultured conjunctival cells into the anterior chamber of the right eye; six normal ferrets were used as controls. Anterograde axonal tracing with cholera toxin B revealed that atrophic damage was evident in the LGN layers receiving projections from OH eyes. Immunohistochemical analysis with antibodies against NeuN, glial fibrillary acidic protein (GFAP), and Iba-1 was performed to specifically label neurons, astrocytes, and microglia in the LGN. Significantly decreased NeuN immunoreactivity and increased GFAP and Iba-1 immunoreactivities were observed in the LGN layers receiving projections from OH eyes. Interestingly, the changes in the immunoreactivities were significantly different among the LGN layers. The C layers showed more severe damage than the A and A1 layers. Secondary degenerative changes in the LGN were also observed, including neuronal damage and astrocyte reactions in each LGN layer. These results suggest that our ferret model of OH is valuable for investigating damages during the retina–brain transmission of the visual pathway in glaucoma. The vulnerability of the C layers was revealed for the first time.

Ocular Examination and Corneal Surface Disease in the Ferret

This article provides a brief, clinically relevant review of corneal surface disease in the ferret. A description of the ophthalmic examination of the ferret is provided. Stepwise descriptions of the most common ophthalmic abnormalities are provided, along with common rule-outs.

Evidence-Based Advances in Ferret Medicine

This literature review covers approximately 35 years of veterinary medicine. This article develops the current state of knowledge in pet ferret medicine regarding the most common diseases according to evidence-based data and gives insight into further axis of research. Literature review was conducted through identification of keywords (title + ferret) with Web-based database searching. To appreciate the methodological quality and the level of evidence of each article included in the review, full-text versions were reviewed and questions addressed in the articles were formulated. Analysis of the articles' content was performed by the authors, and relevant clinical information was extracted.

Reference values for selected ophthalmic tests of the blue-and-yellow macaw (Ara ararauna)

ABSTRACT: The aim of this study was to establish reference values for selected ophthalmic diagnostic tests in healthy blue-and-yellow macaws. We investigated a total of 35 adult macaws (70 eyes) of undetermined sex and with an average weight of 1 kg, who were living in captivity in the Federal District, Brazil. Tear production using the Schirmer tear test (STT), normal conjunctival flora, intraocular pressure (IOP) using a rebound tonometer and horizontal palpebral fissure length (HPFL) were evaluated. In this study, 84.1% of samples were positive for microbial growth. Bacteria, fungi and yeasts were isolated, and Staphylococcus spp. (21.9%) and Bacillus spp. (26.8%) were the most frequently isolated microorganisms. The mean value for STT was 7.6±4.6mm/min in the right eye (OD) and 6.6±4.4mm/min in the left eye (OS) (median = 7,11±0,76mm/min). Mean IOP was 11.4±2.5mm Hg OD and 11.6±1.8mm Hg OS (median = 11.49±0.22mm Hg), prior to anesthesia, and 7.6±2.4mm Hg OD and 7.8±1.8mm Hg OS (median 7.71±0.08mmHg) after anesthesia. The IOP was significantly lower when the animals were under anesthesia as compared to when they were conscious (p≤0.05). Horizontal palpebral fissure length was 11.7±0.1mm OD and 11.8±0.1mm OS (median = 11.72±0.07mm). The STT showed a positive correlation with palpebral fissure measurement for this species. These selected ophthalmic reference values will be particularly useful in diagnosing pathological changes in the eyes of blue-and-yellow macaws.

Establishment of an experimental ferret ocular hypertension model for the analysis of central visual pathway damage

Glaucoma optic neuropathy (GON) is a condition where pathogenic intraocular pressure (IOP) results in axonal damage following retinal ganglion cell (RGC) death, and further results in secondary damage of the lateral geniculate nucleus (LGN). Therapeutic targets for glaucoma thus focus on both the LGN and RGC. However, the temporal and spatial patterns of degeneration and the mechanism of LGN damage have not been fully elucidated. Suitable and convenient ocular hypertension (OH) animal models with binocular vision comparable to that of monkeys are strongly needed. The ferret is relatively small mammal with binocular vision like humans – here we report on its suitability for investigating LGN. We developed a new method to elevate IOP by injection of cultured conjunctival cells into the anterior chamber to obstruct aqueous outflow. Histologically, cultured conjunctival cells successfully proliferated to occlude the angle, and IOP was elevated for 13 weeks after injection. Macroscopically, the size of the eye gradually expanded. Subsequent enlargement of optic nerve head cupping and atrophic damage of LGN projected from the OH eye were clearly observed by anterograde staining with cholera toxin B. We believe the ferret may be a promising OH model to investigate secondary degeneration of central nervous system including LGN.