[Eye changes in the merle syndrome in the dog (author's transl)].
In 44 dachshunds of both sexes, reared and held under identical conditions in order to investigate the effects of the merle gene, ophthalmologic examinations were performed. Eleven extreme dapples with a cutaneous depigmentation beyond 50% (homozygous merle animals, MM) exhibited severe defects in variable forms: Microphthalmia and microcornea, microcoria and corectopia, cataracts and colobomas, rudimentary lenses and ectasia of episcleral vessels. In heterozygous merles with a white percentage of coat color beneath 50% (Mm), lacking tapetum lucidum, depigmented retina, papillary anomaly and ectasia of episcleral vessels were stated, as well as in MM-animals, though not in all. These findings are interpreted as obvious gene dosis effects of the incompletely dominant merle gene which is used to produce a characteric harlequin dappling in many breeds of dogs. With the exception of ectasia of episcleral vessels in a few animals, the homozygous well pigmented controls (mm) displayed none of the anomalies mentioned. The meaning of these results for comparactive medicine and animal protection is discussed.