Genetic aspects of lens luxation in the Tibetan terrier

Analyses were undertaken of 20 cases of lens luxation in British-bred Tibetan terriers, together with a further seven from Sweden. General proband segregation tests showed that the data were consistent with a simple autosomal recessive hypothesis (P = 0.152 +/- 0.0563). This was supported by high levels of inbreeding ranging from 0 to 24.3 per cent, with a mean of 14.3 per cent (SD 5.32 per cent). All affected cases traced back to one or more of three animals (born mid 1950s) on both sides of their pedigrees, all three being breed champions. Inclusion of data from repeat litters between presumed heterozygous animals gave a ratio of 25 lens luxation cases in 121 progeny, which again supported the same genetic theory. The age at onset (three to five years) mitigates against test mating of animals within the breed.