The efficacy of topical prophylactic antiglaucoma therapy in primary closed angle glaucoma in dogs: a multicenter clinical trial.

The ability of either 0.5% betaxolol (1 drop topically, bid; n=31) or a combination of 0.25% demecarium bromide and a topical corticosteroid (gentamicin/betamethasone) (DB/GB; 1 drop of each topically, sid; n=55) to prevent glaucoma in the fellow eye of dogs with unilateral, primary closed angle glaucoma (PCAG) was investigated in a multicenter, open-label, clinical trial. Untreated control dogs (n=20) developed glaucoma significantly sooner (median, eight mos; p less than 0.001) than dogs treated either with DB/GB (median, 31 mos) or betaxolol (median, 30.7 mos). Although DB/GB and betaxolol equally delayed or prevented the onset of glaucoma in the second eye, a less frequent dosing schedule for DB/GB suggests demecarium bromide in combination with a topical corticosteroid may be preferable to betaxolol in preventing PCAG in dogs.

Management of giant retinal tears in dogs.

Sixteen dogs with giant retinal tears resulting in total retinal detachment (360 degrees) underwent unilateral retinal reattachment surgery. In all dogs, complete vitrectomy was performed, and in most, perfluorooctane liquid was used to unroll and flatten the detached retina. Stainless steel tacks were used to anchor the retina to the choroid and sclera. Silicone oil was injected into the vitreous cavity to provide for permanent retinal tamponade. Endophotocoagulation or cryosurgery was used in several dogs to induce formation of permanent chorioretinal adhesions. Retinal attachment was successful in 14 of 16 dogs, and 13 of 14 dogs in which reattachment was successful retained some degree of vision. Complications included formation of cataracts and corneal erosions, development of glaucoma, and dislodgement of tacks.

Treatment of serous retinal detachments associated with optic disk pits in dogs.

Serous retinal detachment, associated with optic disk pit, was diagnosed in 28 eyes of 24 dogs. Xenon arc photocoagulation was used in treatment of the detachment. Of 24 dogs, 21 were Collies. In 23 eyes, retinal detachments affected temporal and/or inferior portions of the retina. In 5 eyes, detachments were predominantly superior and/or nasal. A single photocoagulation treatment resulted in reattachments in 25 eyes. Of the 3 remaining detachments, 2 eyes improved with additional photocoagulation, and 1 eye, which was not treated further, had a complete retinal detachment.

Heredofamilial retinal dystrophy in Guinea baboons. II. Electron microscopic observations.

Electron microscopic study of an inherited retinal degeneration in Guinea baboons disclosed primary pathologic alterations in photoreceptor cells. These changes were first seen in the perifoveal region. Cell death occurred in two forms: hydropic degeneration and densification and/or necrosis. The hydropic type was mainly associated with cone cells, whereas densification and/or necrosis was largely seen in rod cells. Lamellar bodies and granular membrane-bound inclusions were noted in the inner segments and soma. Mitochondria were vacuolated and formed membranous whorls. Bundles of filaments were arranged in parallel array in the soma synaptic endings. Clusters of tubules were present in the synaptic terminals. Preliminary biochemical studies on these animals have yielded no clues to the pathogenesis of the retinopathy.

Heredofamilial retinal dystrophy in Guinea baboons. I. A histopathologic study.

We performed a histopathologic study of a heredofamilial retinal dystrophy in a colony of Guinea baboons. A bull's-eye appearance was noted in the maculas of six baboons of three generations. Histologic examination of 13 eyes from this colony showed primary degeneration of both rod and cone cells initially in the parafoveal region, which subsequently involved the photoreceptor cells of the equator and periphery of the retina. The retinal pigment epithelium and choriocapillaris showed mild changes in the early stages. This disease in baboons was compared with various human retinomaculopathies.

Intraocular granulomas associated with tuberculosis in primates.

Intraocular granulomas associated with tuberculosis were observed in 2 subhuman primates (Ateles geoffroyi and Macaca mulatta). Bacterial cultures from lung tissues at the time of necropsy confirmed the presence of Mycobacterium bovis and M tuberculosis, respectively. The absence of generalized clinical signs in spite of systemic dissemination of the organisms in these cases and the public health significance of tuberculous infections emphasize the importance of proper observation and diagnostic procedures in primate colonies and display collections.

Lens extraction with anterior chamber lens implantation in the macaque.

Three macaques (Macaca arctoides) had anterior chamber implantations with the Choyce Mark VIII lenses in 5 eyes. The eyes were monitored clinically and histologically for approximately 2 years. Histologic sections verified that these lenses were well tolerated in the eyes of the macaques.

Rod-cone dysplasia in the collie.

Rod-cone dysplasia in the Collie was studied. Night blindness developed early (6 wk) and progressed to nearly total blindness by 1 year of age. Tapetal hyper-reflectivity, vessel attenuation, and optic nerve pallor were clinically evident by 6 months of age. Electroretinography demonstrated markedly reduced retinal response as early as 16 days of age. The results of selective breedings conformed to a single recessive pattern of inheritance.

Cone-rod dystrophy in the Guinea baboon.

Three stages of macular degeneration associated with diffuse cone-rod dystrophy have been described in a Guinea baboon (P papio) colony. Clinically, the affected animals displayed abnormal behavior associated with decreased vision. Ophthalmoscopically, the lesion in the macula was the only change observable in early cases; retinal vessel attenuation and optic disc pallor were seen only in the advanced cases. The hyperfluorescence of the maculae was the result of loss of pigment in the pigmented epithelium. Electrophysiology supported a cone-rod sequence of this retinal dystrophy. Histologic examination confirmed the theory that the dystrophy began in the cone outer segment but eventually involved all the photoreceptors.

In vivo erythrocyte sickling in the Japanese sika deer (Cervus nippon): methodology.

The Japanese sika deep (Cervus nippon) proved to be a suitable animal model for the study of acute phases of in vivo erythrocyte sickling. Ophthalmologic studies can be conducted during or after 1 to 6 hours of effective in vivo sickling. Intravenous administration of 1.75 to 3.5% sodium bicarbonate solution at a rate of 500 to 1,000 ml per hour produced a transient state of alkalosis and in vivo erythrocyte sickling in the sika deer. The percentage of sickled erythrocytes increased as the blood pH increased. Concurrently, the packed cell volume decreased. Sickling was enhanced by 100% oxygen ventilation after endotracheal intubation and light anesthetization. After the induction of erythrocyte sickling, a sickling-reversal phenomenon occurred despite continued bicarbonate administration. During the course of this reversal, the percentage of sickled erythrocytes steadily decreased, the venous blood pH decreased, and the packed cell volume slowly increased. Because of the sickling-reversal phenomenon, chronic erythrocyte sickling was not achieved.

Ophthalmic manifestations of induced sickling of erythrocytes in Japanese sika deer (Cervus nippon).

Nine female Japanese sika deer (Cervus nippon) were used in a total of 25 experiments in which sickling was chemically induced. During these experiments, color fundic and color fluorescein photographs were taken. Fundic changes included retinal vascular attenuation, blood column pallor, and decreased tapetal reflectivity. These changes were most likely directly associated with a decreased hematocrit and a generalized shocklike condition. Three deer had a congested appearance in retinal blood vessels and tapetum lucidum. Two of the 3 deer developed serous detachment of the retina. These changes seemingly were associated with severe venous statis; all 3 deer died shortly after the experiment was terminated. These experiments yielded data only for the acutely affected deer. None of the ocular changes could be considered the result of chronic sickling because of the reversal of sickling that occurred despite continued intravenous administration of bicarbonate. None of the deer developed ocular changes characteristic of sickle cell retinopathy in human beings. The changes in human beings probably result from continued stress and prolongation of sickling, and especially from a multiplicity of repeated severe episodes of sickling occurring over many years.