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SUMMARY

Objective

To evaluate the function of the outer retina in Papillons with and without hereditary retinal degeneration.

Animals

45 Papillons, median age 1.7 (range, 0.8 to 5.1) years.

Procedure

Complete physical and ophthalmic examinations were done prior to performing electroretinography under general anesthesia. Full-field electroretinograms (ERG) were recorded, using a special-purpose computer system. Eleven specific ERG responses were recorded, graphed, and evaluated, using age-matched Papillons.

Results

Severely decreased retinal function was detected in 8 Papillons. The youngest affected dog was 1.2 years old. In affected dogs, amplitudes of responses mainly originating from the rod system were severely decreased, compared with those originating from the cone system.

Conclusions

Papillons represent another breed of dog affected by a hereditary photoreceptor degeneration that can be detected at an early age by using ERG. A reliable age for diagnosis using ERG is considered to be 1.5 years.

Clinical Relevance

Thorough and precise ERG procedures and protocols are needed to reliably obtain an early diagnosis of progressive retinal atrophy. (Am J Vet Res 1998;59:221–226)

Free access
in American Journal of Veterinary Research

SUMMARY

The iridocorneal angle of the left eye was investigated in 203 Samoyeds. Comparison was made of judgements of the width of the anterior opening of the ciliary cleft when performing gonioscopy with an objective method of estimation based on measurements on goniophotographs. Results indicated high degree of correlation. Various degrees of narrowness of the iridocorneal angle width were revealed and clinical glaucoma with total-angle closure was found in 6 of 203 dogs. The intraocular pressure was significantly (P < 0.01) higher in eyes with closed iridocorneal angles than in eyes with any other width of the angle. Appearance of the structures of the iridocorneal angle, particularly the pigment bands, indicated extensive individual variation. In approximately 25% of the eyes, dysplasia of the pectinate ligaments of variable degree existed, indicating that this anomaly is common in the Samoyed breed. Significant difference was not evident in intraocular pressure in eyes with different degrees of dysplasia of the pectinate ligaments.

Free access
in American Journal of Veterinary Research

Abstract

Objective—To develop a method to electrophysiologically differentiate heterozygous-carrier Abyssiniancrossbred cats from homozygous-affected Abyssiniancrossbred cats before clinical onset of inherited rodcone retinal degeneration.

Animals—14 back-crossed Abyssinian-crossbred cats of unknown genotype (homozygous or heterozygous) for inherited rod-cone retinal degeneration, 24 agematched mixed-breed control cats, 6 age-matched heterozygous Abyssinian-crossbred cats, and 6 homozygous Abyssinian cats.

Procedure—Electroretinography (ERG) of heterozygous and homozygous cats revealed differences, especially for scotopic recordings. Frequent ophthalmoscopy and ERG (2 to 5 times; at intervals of 3 to 6 months) of back-crossed cats were performed. Amplitudes and implicit times were analyzed by use of a graphic representation of results. Ratios for amplitudes of the b-waves to amplitudes of the awaves (b-wave:a-wave) were compared.

Results—8 back-crossed cats had decreased a-wave amplitudes, increased b-wave implicit times, and abnormal ERG waveforms. Values for the b-wave:awave for the highest scotopic light intensity were significantly higher for those same 8 cats.

Conclusions and Clinical Relevance—The 8 back-crossed Abyssinian-crossbred cats with abnormal results developed fundus changes over time consistent with disease. A graphic representation of ERG results can be used to differentiate between genotypes prior to funduscopic changes. Values for the b-wave:a-wave ratio provide confirmation. These ERG analyses may be applied clinically in the diagnosis of retinal degenerations in various species.

Impact for Human Medicine—Cats with hereditary rod-cone degeneration may be a useful model for comparative studies in relation to retinitis pigmentosa in humans. Similar evaluations of ERG results could possibly be used for humans with suspected generalized retinal degeneration. (Am J Vet Res 2005;66:1914–1921)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To characterize lysosomal storage body accumulation in the retina and brain of Tibetan Terriers with ceroid-lipofuscinosis and determine whether the disease in these dogs is accompanied by impaired retinal function and retinal degeneration.

Animals—Three 7- to 10-year-old Tibetan Terriers with ceroid-lipofuscinosis and 1 healthy 5-year-old Tibetan Terrier.

Procedure—Owners completed a questionnaire to identify behavioral and physical signs indicative of ceroid-lipofuscinosis. Neurologic, behavioral, and ophthalmologic evaluations, including full-field electroretinograms, were performed on each dog. Fluorescence, light, and electron microscopy were performed on specimens of retina, cerebral cortex, and cerebellum of all dogs postmortem.

Results—Behavioral assessments of the affected dogs revealed moderate visual impairment in lowlight conditions but good vision in bright light. On funduscopic evaluation of these dogs, abnormalities detected ranged from none to signs of moderately advanced retinal degeneration. Compared with findings in the control dog, electroretinography revealed depressed rod cell function with some impairment of cone cell function in the affected dogs. Morphologically, disease-specific storage bodies were detected in retinal Müller cells and neurons, particularly in ganglion cells, and in cells of the cerebral cortex and cerebellum in affected dogs. Substantial photoreceptor cell loss and disruption of photoreceptor outer segment morphology appeared to develop late in the disease.

Conclusions and Clinical Relevance—The similarities between ceroid-lipofuscinosis in Tibetan Terriers and some forms of ceroid-lipofuscinosis in humans suggest that the canine disease may have a genetic and biochemical basis similar to that of one of the ceroidlipofuscinosis disorders in humans. (Am J Vet Res 2005;66:67–76)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To characterize the effects of oral administration of a high dose of enrofloxacin to cats.

Animals—24 (12 male and 12 female) young healthy cats.

Procedures—Cats were allocated on the basis of sex into 2 groups (4 males and 4 females/ group) from which 3 subgroups for 3 durations (3, 5, or 7 days) of enrofloxacin (50 mg/kg, PO, q 24 h) or control solution (1 mL of water, PO, q 24 h) administration that began on day −1 were created. Funduscopic examinations were performed daily. Electroretinography (ERG) was performed before and every 2 to 3 days after the start of oral administration. Four cats/study group were euthanized on days 3, 5, and 7, and eyes were collected for light and electron microscopic evaluations.

Results—Neurologic, funduscopic, and ERG abnormalities were evident only in cats administered enrofloxacin. Funduscopic changes (granular appearance or graying of the area centralis) were noticed on or before day 3 (after only 3 days of enrofloxacin administration), with subsequent similar changes along the visual streak. Vascular attenuation (between days 2 and 4) and generalized tapetal hyperreflectivity (between days 5 and 7) followed. Reduction in b-wave ERG amplitude preceded funduscopic changes. Morphologic changes in the photoreceptor layers correlated with duration of enrofloxacin administration, with generalized degenerative changes evident after 3 doses.

Conclusions and Clinical Relevance—The study indicated that a high dose of enrofloxacin (50 mg/kg/d, PO) induced retinal and systemic changes. Enrofloxacin at 10 times the recommended dosage is acutely toxic to the outer retina of clinically normal cats.

Full access
in American Journal of Veterinary Research