Porencephaly with an optic organ abnormality in a beagle dog

A female TOYO beagle dog showed porencephaly and visual organ abnormalities. At necropsy, there was a cavity filled with cerebrospinal fluid in the right cerebral hemisphere and an adhesion area between the cerebral cortex and the skull, which was partially thickened. Additionally, the right optic nerve showed a slight decrease in diameter. Histopathological examination revealed increased glial fibers and collagen fibers, hemosiderin deposition, and an increased number of microglia in the adhesion area, along with a marked reduction of the cerebral parenchyma. In the right eyeball, the retina and optic nerve showed focal atrophy in the nerve fiber layer and inner granular layer to full retinal atrophy and hypoplasia of the myelinated nerve fibers, respectively. Electron microscopic examination revealed hypoplasia of the myelin sheath of nerve fibers in the right optic nerve. This is an extremely rare case of porencephaly and congenital optic nerve hypoplasia, along with independent retinal thinning.     

Unilateral invasive intraocular melanoma with choroidal and optic nerve involvement resulting in bilateral vision loss in a Labrador Retriever

A 10-year-old male castrated Labrador Retriever cross was referred for evaluation of acute vision loss. Ophthalmic examination revealed mild left sided exophthalmos, bilateral resting mydriasis, an absent direct and reduced consensual PLR in the left eye and reduced direct and absent consensual PLR in the right eye. Examination of the cornea and anterior segment with slit lamp biomicroscopy was unremarkable. Indirect fundoscopy revealed a left optic nerve head obscured by a darkly pigmented lesion. Fundic examination in the right eye was unremarkable. Magnetic resonance imaging revealed a smoothly marginated, lobulated cone to irregularly shaped, strongly T1 hyperintense, T2 and T2 fluid-attenuated inversion recovery hypointense, strongly contrast enhancing mass closely associated with the entire left optic nerve, extending across the optic chiasm and into the right optic nerve ventrally. Full clinical staging revealed no evidence of metastasis. Exenteration of the left eye was performed. Histopathology revealed an unencapsulated, poorly demarcated, multilobulated and infiltrative pigmented mass that was effacing the posterior choroid and optic nerve. The mass was composed of a moderately pleomorphic population of heavily pigmented polygonal cells arranged in sheets and clusters, displaying moderate anisocytosis and anisokaryosis. The population of cells contained moderate amounts of abundant brown-black granular pigment consistent with melanin within the cytoplasm. Mitotic figures averaged approximately three per ten 400× fields (2.37 mm²). This is the first report of a melanocytic tumor invading along the optic nerve and tract to result in contralateral vision loss.     

Expression of glial cells molecules in the optic nerve of adult dromedary camel (Camelus dromedarius): A histological and immunohistochemical analysis

The optic nerve (ON) is an important organ in the visual system of animals, which transfers electrical impulses towards the brain from the retina. High enrichment of glial cells in ON is known to support neuron and regulate retinal homoeostasis. However, research on immunohistochemical of glial cells proteins in the camel is scanty in available literature. Hence, the current work is an attempt to investigate the histomorphology of camel ON with regard to the expression patterns of glial fibrillary acidic protein (GFAP), myelin basic protein (MBP) and Iba1 for the three glial subtypes, namely astrocytes, oligodendrocytes and microglia, respectively. Optic nerves from fourteen dromedary camels were dissected and preserved in 10% formalin. Then, the paraffin‐embedding sections were subjected for histochemical and immunohistochemical analysis. Our results demonstrated that ON axons aggregate into fascicles that surrounded by light and densely stained glial cells. Then, we examined the myelin sheath using Heidenhain's and Mallory's phosphotungstic acid staining. Immunoassay results revealed that GFAP is enriched in the ON and distributed evenly, whereas MBP and Iba1 were present at scanty levels. Further analysis of mRNA level of GFAP, MBP and Iba1 in the ON confirmed an elevation of GFAP expression compared to MBP and Iba1. We further found partial co‐localization of different types of glial cells that reflect their coordinated function in the ON. Although our data provide the first evidence for differential expression pattern of glial proteins, further molecular studies still required to reveal the specific function of these molecules in the camel ON.     

Canine and feline retinal lymphoma: a retrospective review of 12 cases

This retrospective study identified 12 cases (6 canine and 6 feline) of ocular lymphoma with extensive retinal involvement and relative sparing of other ocular tissues. Our objectives were to describe the morphologic and immunohistochemical features of retinal lymphoma, assess the degree of correlation to the human counterpart, assign subtypes based on the veterinary‐adapted WHO classification system, and promote accurate reporting of retinal involvement in cases of intraocular lymphoma. Our findings suggest that a distinct retinal tropism is quite rare, representing approximately 1% of all cases of canine and feline ocular lymphoma. No breed or sex predispositions were identified. The mean age of the affected animal was 7 years (range 4–10) and 11 years (range 6–19) for dogs and cats, respectively. Nine cases (5 canine and 4 feline) were classified as diffuse large B‐cell lymphoma (DLBCL) subtype. The remaining cases were classified as peripheral T‐cell lymphoma (PTCL).     

Rapid diagnosis of retina and optic nerve abnormalities in canine patients with and without cataracts using chromatic pupil light reflex testing

Objective To develop fast and reliable testing routines for diagnosing retina and optic nerve diseases in canine cataract patients based on chromatic properties of the pupillary light reflex response. Procedures Seventy‐seven canine patients with a history of cataract and decreased vision (43 patients with cataracts and no evidence of retina or optic nerve disease, 21 patients with cataracts and retinal degeneration [RD], 13 patients with cataracts and retinal detachment [RDT]), 11 canine patients with optic neuritis (ON) and 23 healthy dogs were examined using chromatic pupillary light reflex (cPLR) analysis with red and blue light and electroretinography. Results Electroretinography analysis showed statistically significant deficits in a‐ and b‐wave amplitudes in dogs with cataracts and RD, or cataracts and RDT, when compared to dogs with cataracts without evidence of retinal abnormalities. Evaluation of b‐wave amplitudes showed that presence of 78.5‐μV (or lower) amplitudes had high sensitivity of 100% (95% CI: 87.2–100%) and high specificity of 96.7% (95% CI: 88.4–100%) in RD and RDT. Evaluation of cPLR responses using red light showed that presence of the pupil end constriction diameter of 5.5 mm (or higher) had moderately high sensitivity of 76.5% (95% CI: 50.1–93.2%) and high specificity of 100% (95% CI: 91.2–100%) in detecting RD and RDT. Optic neuritis patients had absent cPLR responses, regardless of the visual status. Conclusions and Clinical Relevance Chromatic evaluation of the pupillary light reflex is a rapid and accurate test for diagnosing retina and optic nerve diseases in canine patients.     

Bilateral traumatic optic nerve avulsion in a Thoroughbred gelding

This report describes an unusual case of acute blindness following traumatic head injury in a mature horse. The horse fell over backwards and subsequently presented with bilateral blindness and epistaxis. Vision did not return following medical supportive therapy and euthanasia was elected. Post mortem findings revealed a basisphenoid fracture and bilateral optic nerve avulsion rostral to the optic chiasm, an uncommon presentation of traumatic blindness not previously reported in the horse.     

Comparative retinal ganglion cell and optic nerve morphology

The optic nerve is divided in four regions: intraocular, intraorbital, intracanalicular, and intracranial. The vertebrate retinal ganglion cells are classified by morphology, physiology and soma size. Species differences and similarities occur with retinal ganglion cells. Alpha retinal ganglion cells have large somata, large dendritic fields, large-diameter axons, and are most dense in the peripheral retina. Beta retinal ganglion cells have smaller diameter somata, smaller dendritic fields, small diameter axons, and predominate in the central retina. Gamma retinal ganglion cells are a heterogenous class of cells and have small diameter axons, and slow axon conduction velocities. The spatial distribution and organization of the retinal ganglion cells extends retinotopically through the nerve fiber layer, optic nerve, optic chiasm, optic tract, lateral geniculate nucleus, and visual cortex. The retinal nerve fiber layer thickness decreases from the optic disk toward the periphery of the retina. The retrobulbar optic nerve axon counts and axon density vary by species, with larger nerves having higher axon counts. Decussation of the optic nerve axons at the optic chiasm varies with 100% decussation in most birds and fish, 65% in cats, 75% in dogs, 80–90% in large animals, and 50% in primates. Centrifugal axons also occur in the optic nerve and may represent a method by which the brain can influence retinal activity.     

A review of orbital and intracranial magnetic resonance imaging in 79 canine and 13 feline patients (2004-2010)

Objective To review the distribution of orbital and intracranial disease in canine and feline patients undergoing magnetic resonance imaging (MRI) following referral to a veterinary ophthalmologist and to correlate results of MRI with pathologic conditions including neoplasia, suspected optic neuritis (ON) and orbital cellulitis. Recognized and emerging imaging techniques are reviewed. Procedure Medical records of 79 canine and 13 feline patients were reviewed. Results Neoplasia was diagnosed in 53/92 (57.6%) of patients. The most prevalent types of neoplasia were carcinoma (16/53, 30.1%), sarcoma (11/53, 20.8%), lymphoma (8/53, 15.1%) and presumptive meningioma (9/53, 17.0%). Carcinomas and sarcomas were characterized by bony lysis and intracranial/sinonasal extension. Lymphoma was generally unilateral, less invasive and originated from the ventromedial orbit. Intracranial masses representing presumptive meningiomas frequently exhibited a ‘dural tail’ sign. Diagnosis of suspected ON was made in 13 of 92 (14.1%) patients. Results of MRI in patients with suspected ON included unilateral optic nerve hyperintensity (3/13, 23.0%), bilateral optic nerve hyperintensity (1/13, 7.7%) and optic chiasmal hyperintensity (3/13, 23.0%). Seven suspected ON patients demonstrated intracranial multifocal patchy contrast enhancement (7/13, 53.8%). Diagnosis of orbital cellulitis was made in 12/92 (13.0%) patients. Conclusions Orbital neoplasia was the most common pathologic condition detected. Essential Roentgen characteristics are helpful when diagnosing pathologic processes and providing prognoses in cases of orbital or intracranial disease. Magnetic resonance imaging comprises an important diagnostic component in cases of suspected ON. Emerging contrast and functional MRI techniques as well as SI data may increase our ability to characterize disease processes.     

The future of canine glaucoma therapy

Canine glaucoma is a group of disorders that are generally associated with increased intraocular pressure (IOP) resulting in a characteristic optic neuropathy. Glaucoma is a leading cause of irreversible vision loss in dogs and may be either primary or secondary. Despite the growing spectrum of medical and surgical therapies, there is no cure, and many affected dogs go blind. Often eyes are enucleated because of painfully high, uncontrollable IOP. While progressive vision loss due to primary glaucoma is considered preventable in some humans, this is mostly not true for dogs. There is an urgent need for more effective, affordable treatment options. Because newly developed glaucoma medications are emerging at a very slow rate and may not be effective in dogs, work toward improving surgical options may be the most rewarding approach in the near term. This Viewpoint Article summarizes the discussions and recommended research strategies of both a Think Tank and a Consortium focused on the development of more effective therapies for canine glaucoma; both were organized and funded by the American College of Veterinary Ophthalmologists Vision for Animals Foundation (ACVO‐VAF). The recommendations consist of (a) better understanding of disease mechanisms, (b) early glaucoma diagnosis and disease staging, (c) optimization of IOP‐lowering medical treatment, (d) new surgical therapies to control IOP, and (e) novel treatment strategies, such as gene and stem cell therapies, neuroprotection, and neuroregeneration. In order to address these needs, increases in research funding specifically focused on canine glaucoma are necessary.     

Quantitative study of the optic nerve in buffaloes (Bos bubalis)

The total number, distribution and size of the optic axons of the buffalo (Bos bubalis) were studied in five optic nerves using light and transmission electron microscopes. Semithin sections were cut at 0.40 μm with an ultramicrotome and stained with 0.3% toluidine blue for light microscopic analysis. The ultrathin sections were cut at 70 nm, mounted on copper mesh grids (No. 200) and stained with saturated solution of uranyl acetate dihydrate and examined with the transmission electron microscope. The optic axons were assessed in 10 regions of roughly equal area. The total number of optic fibers was estimated on semithin and ultrathin sections. The measurements of the axonal diameters were made on electron micrographs taken from various regions across the optic nerve. The mean value of the total number of optic axons calculated was 1 397 099 ± 10 995 and 1 584 255 by light and electron microscopes, respectively. There was very little difference in the density of the optic fibers between the 10 regions of the optic nerve. The optic nerve area ranged from 18.2 to 22.4 mm² (mean, 21.3 mm²). The diameters of the optic axons ranged from 0.5 to 12.3 μm (mean, 3.3 μm).     

Spectral domain optical coherence tomography (SD-OCT) assessment of the healthy female canine retina and optic nerve

Objective To provide normative data for canine whole retinal thickness (WRT), nerve fiber layer thickness (NFL), photoreceptor layer thickness (PR), and outer nuclear layer thickness (ONL) using spectral domain optical coherence tomography. Animal studied: Twelve healthy adult intact female beagles. Procedure Horizontal volume scans through the area dorso‐temporal from the optic nerve (superior retina), and the area ventro‐temporal from the optic nerve (inferior retina) were used to evaluate the thickness of retinal NFL, PR, ONL, and WRT. Peripapillary circular scans were used to evaluate NFL thickness. Statistical analyses were performed to compare the thickness of the individual layers between the superior and inferior retina (paired t‐test). One‐way analysis of variance (ANOVA) was used to compare the thickness of peripapillary NFL between the superior, inferior, temporal and nasal quadrants of the circle scan. Results The WRT, PR, and NFL thickness were greater in the superior than in the inferior retina (198.7 ± 9.6 μm vs. 164.4 ± 6.4 μm, P < 0.0001; 95.5 ± 6.5 μm vs. 78.8 ± 7.4 μm, P < 0.0001; and 26.4 ± 1.6 μm vs. 25.0 ± 1.9 μm, P = 0.0236, respectively). No statistical difference was found between the ONL thickness of the superior and inferior retina (50.1 ± 6.4 μm vs. 44.3 ± 3.6, P = 0.0578). Peripapillary NFL thickness showed a similar tendency as the linear scans, with the superior quadrant having the greatest thickness (91.26 ± 7.0 μm) and the inferior quadrant being the thinnest (76.42 ± 9.2 μm) (P < 0.001). Conclusions Results of our in vivo studies showed significant differences between thickness values for the superior (tapetal) and inferior (nontapetal) retinal regions.     

Cytological features of canine ovarian tumours: a retrospective study of 19 cases

The cytological features of 19 histologically confirmed canine ovarian tumours were retrospectively examined. Seven cases were cytologically classified as papillary adenocarcinoma, eight cases as granulosa cell tumours, two cases as mature ovarian teratomas, one case as a dysgerminoma and one case as a mixed granulosa cell tumour/dysgerminoma. On cytology, papillary adenocarcinoma was characterised by a papillary glandular pattern and tight cohesiveness. Granulosa cell tumours showed monolayered clusters of loosely cohesive granulosa cells. Call-Exner-like bodies were found in five of seven cases. Granulosa cells appeared to be heterogeneous and usually contained several intracytoplasmic vacuoles. Teratoma was characterised cytologically by keratin debris (two cases) and a mixture of epithelial cells with sebaceous, basaloid, columnar/palisading or ciliated appearance (one case). The dysgerminoma contained severely atypical round cells admixed with small lymphocytes. The mixed dysgerminoma/granulosa cell tumour had a mixture of germinal and granulosa cells. Cytological diagnosis was in agreement with histopathology in 18 of 19 (94.7 per cent) cases.     

Comparative optic nerve physiology: implications for glaucoma, neuroprotection, and neuroregeneration

The axoplasm of optic nerve axons moves bidirectionally at various speeds along an intra-axonal pressure gradient from the retinal ganglion cell (RGC) somata toward its synapse, and from the synapse towards the RGC somata. The axoplasmic flow of optic nerve axons is precarious even at normal intraocular pressures (IOP) as it moves from the intraocular optic nerve through the scleral lamina cribrosa to the intraorbital optic nerve. The scleral lamina cribrosa is not simply a porous region of the sclera but a specialized extracellular matrix of the central nervous system whose movement during fluctuations in IOP can affect optic nerve axoplasmic flow. The abundant optic nerve blood supply maintains adequate optic nerve head perfusion through a process of vascular autoregulation. Glaucoma is associated with reduced optic nerve axoplasmic flow and compromised optic nerve circulation such that RGC death due to glutamate excitotoxicity and neurotrophin deprivation result.     

The radiological features of canine Cushing's syndrome: a review of forty-eight cases

The radiological signs which have been reported in association with canine Cushing's syndrome are reviewed. The incidence of these changes in 48 dogs affected with this condition is reported and the contribution of radiography to diagnosis, prognosis and management is discussed.     

Histopathologic features of canine uremic gastropathy: a retrospective study

Uremic gastritis is a term commonly used to describe the gastrointestinal signs and histopathologic changes associated with renal failure in the dog. This retrospective study reviews the clinical, serum biochemical, and postmortem histopathologic data from 28 dogs with renal failure to determine the prevalence of gastric histopathology, characterize the gastric histopathology, and identify associations between gastric histopathology and serum concentrations of blood urea nitrogen (BUN), creatinine (Cr), calcium-phosphorus product (Ca x Phos), and hematocrit. Affected and control dogs with available renal and gastric tissue, serum biochemistry data, and urinalysis data were identified over a 10-year period (1992-2002) in the pathology department postmortem examination database at the Cornell University College of Veterinary Medicine. The serum biochemistry data and histopathologic findings were scored as normal, mild, moderate, and severe. All affected dogs had derangements of BUN, Cr, or Ca x Phos with gastric histopathology in 22 of 28 dogs (79%). Dogs with renal failure had a higher prevalence of gastric histopathologic changes compared with the control group. Associated histopathologic changes in the stomach were edema (P = .008), mineralization (P = .03), and vasculopathy (P = .03). Only 1 dog had evidence of gastric ulceration. Gastric necrosis was an uncommon finding (4/28, 14%). Gastric histopathology appears to be common in dogs with renal failure and is associated with increasing severity in the serum biochemistry data. Unlike humans with renal failure, in whom gastric ulceration predominates, gastric necrosis and ulceration appear to be uncommon in dogs with renal failure.