Progressive retinal atrophy in the Tibetan spaniel in Norway and Sweden.

Progressive retinal atrophy of the late onset type was diagnosed in 51 Tibetan spaniels in Norway and Sweden. At the time of diagnosis they were between three and seven years old; however, early ophthalmoscopic changes caused by the thinning of the retina could sometimes be difficult to observe because of the partial or total lack of the tapetum in many of the dogs. The disease developed rapidly, approximately one year passing from the initial clinical signs of night blindness to complete loss of vision. Twenty-four male and 27 female dogs were affected. All the affected dogs were interrelated and could be traced back to common English ancestors. On the basis of pedigree studies, an autosomal recessive mode of inheritance is postulated. Information on 15 diagnosed cases of the condition in other countries shows that the disease may be considered a worldwide problem in the Tibetan spaniel.