There are several different "dominant blue eyes" (DBE) mutations. These are not fully identified and catalogued, but they are known to be forms of white spotting. In some DBE mutations there is a distinctive pattern of white marking e.g. white tail tip with white toes, white forequarters and coloured hindquarters. In others, the white spotting is localised to the eyes; the eyes are part of the embryo surface so absence of melanin at that location of the skin surface gives rise to blue eyes. It is important to work with only one gene and not combine multiple DBE genes into one breeding line. A recent case study has found it is important to not mix the Altai DBE gene with the white spotting gene.

None of this is to assign blame or fault, but these are observations that suggest tear duct issues associated with some DBE cats that also have the white spotting gene. It is worth paying close attention to tear drainage in DBE cats, and noting observations, in case there is any link. DBE has incomplete penetrance, so some genetically DBE cats may have green or odd eyes and these colour eyes seem to have normal tear ducts. In odd-eyed cats, the tear ducts were absent only on the blue-eyed side. It is recommended that blue-eyed DBE cats are checked for normal tear ducts before being used in breeding.

Some breeders noticed a link between the Altai gene and tear duct problems. This has not been confirmed in all cats with the Altai gene so it may be associated with particular breeding lines only. The cats concerned do not have short noses as found in Persians, Exotics or extreme British, so brachycephaly can be ruled out as a cause. There is a fear that if DBE is added to a breed that still has an open studbook (to add new blood), such as the Siberian, it could also introduce tear duct problems which would take generations to eliminate from a breed. Although few breeders have reported tear duct problems, it may be a hidden problem linked to some DBE lines.

DBE Siberian Male from Russia, Altai F4 generation, Black Tabby and white. Weeping eyes when acquired at age 4 months. Eyes normally spaced (wider spacing in kittenhood, but this is not unusual). Taken for vet treatment for conjunctivitis due to owner having to wipe away tears. Vet found that this cat has tear glands, but no tear drainage ducts. He was bred once (now neutered), resulting in 6 kittens from a blue-tabby-and-white Siberian (not DBE). The kittens had normal nose lengths and a higher degree of white than the parents.

Girl 1 - 2 blue eyes. Black tabby bicolour. Eyes weep heavily.
Girl 2 - 2 blue eyes. Black tabby harlequin. Eyes weep.
Girl 3 - 2 blue eyes. Black tabby harlequin. One eye weeps slightly, other eye does not weep. Dry nose, prone to crusting.
Girl 4 – blue tabby point: one weeping eye, dry nose.
Boy 5 - blue tabby point with white. Two green eyes. No weeping, normal moist nose.
Boy 6 - blue silver van pattern. Two blue eyes, no weeping. Dry nose prone to crusting. The blue eyes without weeping may be due to the white spotting gene rather than the incompletely penetrant Altai gene.

The DBE stud cat’s breeder provided a replacement DBE stud (black tabby with low degree of white, odd eyes), though his pedigree doesn’t show the Altai origin of his blue eyes. This male has a weeping blue eye, but non-weeping yellow eye. The weeping was not apparent at his cattery of origin. Vet tests found that the blue eye did not have a tear drainage duct, but the yellow eye had a normal tear drainage duct. He has bred to 2 females and kittens are expected.