Introduction
- Retinal pigment epithelial dystrophy (RPED) is now the preferred name.
- Cause : hereditary; autosomal recessive inheritance.
- Genetic defect leading to dysfunction of retinal pigment epithelium (RPE), the cell layer adjacent to the photoreceptors that is responsible for maintaining photoreceptor function → inability of dystrophic RPE cells to degrade photoreceptor outer segments (POS) → photoreceptor degeneration.
- Diagnosis : clinical signs, ophthalmoscopy, electroretinography. Nutritional influence → vitamin E deficiency gives similar lesions and maybe implicated here too.
- Treatment : Vitamin E supplementation may be recommended but therapeutic effects unknown.
- Prognosis : deterioration is probably influenced by many factors; affected animals lose their central field of vision but maintain peripheral sight.
Diagnosis
Clinical signs
- Ophthalmoscopy reveals bilateral light brown, rounded spots in the peripheral tapetum initially, with progression to the area centralis.
- Tapetal reflectivity increases late in the disease.
Diagnosis
Differential diagnosis
- Chorioretinitis, vitamin E deficiency.
- Congenital stationary night blindness (CSNB) in Briards
: similar ophthalmoscopic appearance. CSNB is due to abnormality in RPE65 gene (genetic testing available at www.optigen.com ).
Sequelae
Prognosis
- All affected animals develop central blindness.
Expected response to treatment
- Slow progression.
Reasons for treatment failure
- Blindness.
Sources
Publications
Refereed papers
- Recent references from PubMed.
- McLellan G J et al(2003) Clinical and pathological observations in English cocker spaniels with primary metabolic vitamin E deficiency and retinal pigment epithelial dystophy. Vet Rec 153 (1), 287-292 PubMed.
- Watson P et al(1993) Hypercholesterolemia in Briards in the United Kingdom. Res Vet Sci 54 (1), 80-85 PubMed.
Other sources of information
- Narfstrom K & Petersen-Jones S M (2007) Diseases of the Canine Ocular Fundus. In: Veterinary Ophthalmology. 4th edn. Ed K N Gelatt, Blackwell Publishing, Iowa, USA, pp 944-1025.
