Multifocal retinal dysplasia in the Syrian hamster LAK:LVG (SYR)

Multifocal retinal dysplasia was diagnosed clinically in twenty-four of twelve hundred (2.0% incidence) LAK:LVG (SYR) Syrian Hamsters. The affected hamsters were part of twelve hundred animals to be used in oncogenic studies. Ther dysplastic retina were detected during ophthalmoscopic examinations of hamsters as young as 6 weeks and as old as 9 months. Ophthalmoscopically, the dysplastic foci varied from retinal streaks, sometimes called vermiform, to small, generally circular areas of cream-colored depigmentations. Blindness or othe apparent visual defects were not seen nor were the dysplasias associated with a generalized syndrome of disease. Histologic examination of the affected hamsters revealed focal dysplasias limited to the retina and were manifested as invaginations and rosette-like structures composed of elements of the photoreceptor layer, outer limiting membrane and outer nuclear layer. This paper describes the first incidence of a congenital retinal dysplasia found in an outbred strain of Syrian Hamster LAK:LVG (SYR), and correlates the ophthalmoscopic appearance and histopathology. In addition, a procedure for maintaining prolonged mydriasis for funduscopic photography is presented.