In this case, the deafness and blindness are linked to having two copies of the merle gene, which disrupts pigmentation and produces these health defects.All black and blue merle dogs have black noses, eye rims, and lips. In this case, the deafness and blindness are linked to having two copies of the merle gene, which disrupts pigmentation and produces these health defects.All black and blue merle dogs have black noses, eye rims, and lips. All red and red merle dogs have liver or brown noses, eye rims, and lips. Also, great variety is seen in the Aussie's eye color, and they are often heterochromatic. An early nickname for the breed was 'ghost-eye dog'. Although many believe that only dogs with blue eyes have eye problems, it is not correct. Due to the contrast between eye problems and blue eyes, eye conditions in blue-eyed dogs are much easier to spot.Not all homozygous merles are affected, but most are, making the breeding of two merles a very touchy subject.