Day-blindness in three dogs: clinical and electroretinographic findings.

A 6-month-old Rhodesian ridgeback-cross, a 6-year-old Chihuahua and a 12-month-old Australian cattle dog were presented to the authors with a history of colliding with obstacles in daylight. Ophthalmic examination was normal and all three dogs successfully negotiated obstacle courses in dim light. In daylight the dogs became suddenly blind and repeatedly collided with obstacles. Elecroretinography (ERG) revealed no retinal activity to high frequency (30 Hz), bright intensity blue light retinal stimulation by any dog, confirming cone dysfunction. Achromatopsia has previously been recorded in Alaskan malamutes and miniature poodles. This clinical case series illustrates the characteristic behavioral presentation and the electroretinographic findings of severe day-blindness and demonstrates that this condition may exist in other breeds of dogs.