Acute Blindness.

Sudden loss of vision is an ophthalmic emergency with numerous possible causes. Abnormalities may occur at any point within the complex vision pathway, from retina to optic nerve to the visual center in the occipital lobe. This article reviews specific prechiasm (retina and optic nerve) and cerebral cortical diseases that lead to acute blindness. Information regarding specific etiologies, pathophysiology, diagnosis, treatment, and prognosis for vision is discussed.

Magnetic resonance imaging characteristics of equine head disorders: 84 cases (2000-2013).

The equine head is an anatomically complex area, therefore advanced tomographic imaging techniques, such as computed tomography or magnetic resonance imaging (MRI), are often required for diagnosis and treatment planning. The purpose of this multicenter retrospective study was to describe MRI characteristics for a large sample of horses with head disorders. Horses imaged over a period of 13 years were recruited. Eighty-four horses met the inclusion criteria, having neurological (n = 65), sinonasal (n = 14), and soft tissue (n = 5) disorders. Magnetic resonance imaging accurately depicted the anatomy and allowed identification of the primary lesion and associated changes. There were good correlations between MRI findings and intraoperative or postmortem results. Magnetic resonance imaging showed the exact localization of the lesions, their size, and relation to surrounding structures. However, in the neurological group, there were 45 horses with no MRI abnormalities, 29 of which had a history of recurrent seizures, related to cryptogenic epilepsy. Magnetic resonance imaging was otherwise a valuable diagnostic tool, and can be used for studying a broad range of head disorders using either low-field or high-field magnets.

Contralateral optic neuropathy and retinopathy associated with visual and afferent pupillomotor dysfunction following enucleation in six cats.

PURPOSE: To investigate contralateral optic neuropathy and retinopathy following enucleation in 6 cats. METHODS: Retrospective study. The medical records of cats with contralateral visual and afferent pupillomotor dysfunction following enucleation presented to the Animal Health Trust (AHT), Newmarket, UK, between January 1994 and January 2010 were reviewed. Information recorded included history, signalment, ophthalmic findings, electroretinography (ERG) (2/6) and MRI (3/6) findings and long-term outcome. Pearson's chi-square tests were used to compare breed proportions (P < 0.05). RESULTS: Six cats aged 1.5 to 11 (median 5.5) years presented with mydriasis and/or visual deficits noted immediately following enucleation. Enucleation involved optic nerve (ON) ligation in all of the four cases for which this information was available. Ophthalmic findings included mydriasis with absent pupillary light reflex (PLR) (4/6), incomplete PLRs (2/6), absence of dazzle reflex (4/6) and absence of menace response (4/6). Funduscopy initially revealed multifocal peripapillary retinal lesions, with subsequent progressive optic nerve head (ONH) and retinal atrophy. ERG recordings revealed normal outer retinal function at 6 and 22 weeks (2/2). On MRI, the optic chiasm (OC) ipsilateral to the enucleation could not be identified and the contralateral OC was atrophied (3/3). CONCLUSIONS: The acute afferent ON deficits following enucleation, progressive ONH atrophy, normal outer retinal function and MRI demonstrating OC pathology are consistent with chiasmal injury due to traction on the ON during enucleation. Rostral traction on the globe to facilitate ON ligation is contraindicated in cats.

Bilateral vision loss in a captive cheetah (Acinonyx jubatus).

The following case report describes a 1-year-old female cheetah (Acinonyx jubatus) with bilateral blindness and unresponsive pupils. For comparison, a second healthy 2.5-year-old male cheetah without visual deficits was also examined. Clinical examination of both animals included biomicroscopy, indirect ophthalmoscopy, tonometry, and electroretinography. The young female cheetah showed no menace response, no direct or indirect pupillary light reflex, and no dazzle reflex in either eye. Fundus lesions, as detected by indirect ophthalmoscopy, are described for the female animal. In both eyes, the fundus color was green/turquoise/yellow with multiple hyperpigmented linear lesions in the tapetal area around the optic nerve. The optic nerve head was dark gray and about half the normal size suggesting bilateral optic nerve hypoplasia and retinal dysplasia or differentially optic nerve atrophy and chorioretinal scarring. The ERG had low amplitudes in the right eye but appeared normal in the left eye compared with the male cheetah. Blood levels did not suggest current taurine deficiency. This is addressed to some degree in the discussion. Bilateral optic nerve hypoplasia or optic nerve atrophy is a rare anomaly in cats and has not yet been described in a cheetah.

Functional and structural changes in a canine model of hereditary primary angle-closure glaucoma.

PURPOSE: To characterize functional and structural changes in a canine model of hereditary primary angle-closure glaucoma. METHODS: Intraocular pressure (IOP) was evaluated with tonometry in a colony of glaucomatous dogs at 8, 15, 18, 20, and 30 months of age. Retinal function was evaluated using electroretinography (scotopic, photopic, and pattern). Examination of anterior segment structures was performed using gonioscopy and high-frequency ultrasonography (HFU). RESULTS: A gradual rise in IOP was observed with an increase in age: 8 months, 14 mm Hg (median value); 15 months, 15.5 mm Hg; 18 months, 17.5 mm Hg; 20 months, 24 mm Hg; 30 months, 36 mm Hg. Provocative testing with mydriatic agents (tropicamide and atropine 1%) caused significant increases in IOP (35% and 50%, respectively). HFU analysis showed complete collapse of iridocorneal angles by 20 months of age. Scotopic and photopic ERG analysis did not reveal significant deficits, but pattern ERG analysis showed significantly reduced amplitudes in glaucomatous dogs (glaucoma, 3.5 +/- 0.4 muV; control, 6.2 +/- 0.3 muV; P = 0.004; Student's t-test). Histologic analysis revealed collapse of the iridocorneal angle, posterior bowing of the lamina cribrosa, swelling and loss of large retinal ganglion cells, increased glial reactivity, and increased thickening of the lamina cribrosa. CONCLUSIONS: Canine hereditary angle-closure glaucoma is characterized by a progressive increase in intraocular pressure, loss of optic nerve function, and retinal ganglion cell loss.

Ultrasonographic findings in 50 dogs with retrobulbar disease.

Records of 50 dogs with signs of retrobulbar disease that had ultrasonography and diagnosis based on results of cytopathology or histopathology were reviewed retrospectively. Abnormalities were identified ultrasonographically in 43 (86%) dogs. Mass effect was identified in 42% of dogs with neoplasia and 30% of dogs with abscess. Ten of 11 (91%) orbital bone lesions were in dogs with retrobulbar neoplasia. A cavitary lesion was recognized ultrasonographically in 75% of dogs with salivary mucocele and 50% of dogs with retrobulbar abscess. Neoplasms occurred predominantly on the ventral or medial aspect of the orbit, or both, which reflects invasion by nasal or sinus neoplasms. Presence of orbital bone lesions or a mass on the medial aspect of the orbit suggests neoplasia; however, other ultrasonographic signs were nonspecific.

Optic nerve dysplasia associated with meningeal defect in Sprague-Dawley rats.

Unilateral and bilateral dysplasias of the optic nerve (ON) were observed in 20/114 male and 14/110 female Sprague-Dawley rats at 12 weeks of age. Grossly, the intracranial segment of the affected ON had nodular thickening, bifurcation, and curvature. Nodular thickenings were seen in 20 males and 11 females. One female had a bifurcated ON. Curvature was observed in the left ONs of two females. Of 34 ON dysplasias, 12 ONs tapered off into a thin filament at the portion anterior to the dysplastic lesions. The intraorbital segments of the ONs in 33 rats were also reduced in size and were hardly recognizable in the meningeal sheath in 10 rats. Both eyeballs appeared normal in all the animals examined. Histologically, nerve fibers in intracranial and intraorbital segments of the ONs that appeared as slender filaments were markedly reduced in number. Nerve fibers in nodular thickenings were intertwined in haphazard fashion, forming scrollworklike structures. The meningeal sheaths in intracranial segments of the ONs in 15 rats and in intraorbital segments in eight rats were partially missing. The naked portion of the ON protruded into the meningeal spaces or gaps. The data indicate that developmental failures in the ON may have been induced due to insufficient blood supply through the meningeal covering or herniation of growing nerve fibers into the defective meninges. However, etiology and pathogenesis of this condition remain unclear.

Central amaurosis induced by an intraocular, posttraumatic fibrosarcoma in a cat.

A 12-year-old, castrated male, domestic shorthair cat with a previous penetrating trauma to the left globe which progressed to a phthisical eye presented for acute blindness. Ophthalmic examination and electroretinography of the right eye were found to be normal. Following euthanasia, gross and microscopic examinations were completed. A left intraocular, posttraumatic fibrosarcoma with extension to the optic nerve and chiasm and induced right optic nerve fiber degeneration at the optic chiasm with necrosis leading to central amaurosis were diagnosed.

Update on llama medicine. Ophthalmology.

Review of the limited literature on camelid eyes suggests they are anatomically similar to those of domestic livestock species, except they lack meibomian glands and have iridial folds (rather than corpora nigra). The microbial flora of the healthy camelid conjunctival sac also appears to be similar to those of domestic livestock and pets, except that no Mycoplasma have been isolated from camelids. Ocular diseases for which camelids are presented to veterinarians are numerous and varied. The most frequently presented conditions are ocular trauma and congenital abnormalities. Trauma to cornea, conjunctiva, eyelids, and sclera has been reported. Therapies for these injuries are the same as for other animals. Most congenital abnormalities are cataracts and optic nerve colobomas, but congenital eyelid defects, conjunctival cysts, and multiple ocular defects have been reported. Although these conditions are not demonstrably hereditary, breeding of animals with congenital ocular defects is strongly discouraged. Intraocular inflammatory diseases are seen commonly in camelids. Uveitis and chorioretinitis may cause permanent visual loss, usually with no indication of cause. Equine herpesvirus 1 has been isolated from camelids with severe ocular inflammation and is a known cause of chorioretinitis and neurologic abnormalities. Systemic aspergillosis causes severe chorioretinitis in alpacas. More research is needed to improve our understanding of ocular physiology and pathology in camelids. Genetic studies also are needed to establish hereditary patterns of ocular maldevelopment. Additional information from researchers and practitioners should improve our ability to recognize and treat ocular disease in camelids.

Glioma of the optic nerve with intraocular and intracranial involvement in a dog.

An anaplastic glioma of the optic nerve, involving the globe, optic chiasma and brain in a 3 1/2-year-old Labrador Retriever is described. The tumour consisted of lobules of small, dark cells intersected by a delicate fibrovascular stroma. There was a high degree of anaplasia and an average of 19 mitoses per x 200 field. The clinical signs were exophthalmos and mydriasis, followed several months later by blindness and, only terminally, by signs of brain involvement.

Neonatal ophthalmology.

This discussion of normal and abnormal findings on routine ophthalmic examination of the foal should prove useful to the equine practitioner who must provide counsel to the concerned owner and/or breeder. Early diagnosis and treatment of ocular abnormalities improve the prognosis for continued function and aid determination of the significance of lesions observed in later life.

Neuroepithelial tumor of the optic nerve in a horse.

A nine-year-old horse was presented with severe exophthalmos of the right eye and a large mass in the vitreal cavity. The affected globe was enucleated and two months following surgery the horse was euthanized because of spread of the tumor into the calvarium producing compression of the brain stem and neurologic signs. Examination of tumor tissue by light and electron microscopic examination showed a mixed neoplasm of primitive neuroepithelium.