Page 102 - JRT Magazine - 2023 Issue 2

Education

Miscellaneous

Blue eye(s) White iris – indicates a lack of pigment
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production in the eye area, which causes the
There are four possible ways that a healthy dog eyes to appear blue.
can have blue eyes. Emphasis on ‘healthy’ since
there are several medical conditions that can For purebred Jack Russell Terriers, #1, #2 and #3
cause the appearance of blue eyes. do not apply. Thus, when a JRT/ Russell Terrier
ends up with one or both eyes blue, it is due to
The most common medical condition that can a lack of pigment. Lack of pigment is associated
make an eye have a blue cast is corneal edema. with the Sp gene.
When fluid accumulates within the stroma of
the cornea, light that enters the eye is scattered, Eye color is determined by the amount of pigment
which gives the cornea a blue appearance. located in the front part of the eye’s iris. Though
Endothelial corneal dystrophy, glaucoma, lens eye colors vary, the iris contains only eumelanin
luxation, trauma, and inflammatory conditions pigment. If a dog’s irises contain a lot of pigment,
can all cause corneal edema, resulting in an eye the eyes will appear nearly black or brown; if
that appears blue. they have little pigment, the eyes will be lighter
in color (light tan, amber, or golden), and if no
For dogs with healthy eyes, which just happen pigment--blue. If a dog is bb at the B locus, the
to be blue, the reasons must be one of the eumelanin will be modified and may make the
following: eyes carry a greenish cast (remember that these
dogs will have a liver nose and no black hairs on
Albinism – Full albinism has never been the body—it all changes to liver.)
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confirmed in dogs, but partial albinism has
been seen in dogs carrying the merle gene plus Young animals often have blue or gray eyes soon
the piebald gene. Unlike rodents, dogs don’t after birth because their eye pigmentation hasn’t
have pink eyes when they lack pigment; they fully developed. The OCA2 gene comes into play
are more similar to human albinos, who have because it determines how much pigmentation
blue eyes when the pigment isn’t present. Dog is in the eye.
Genetics reports there are no confirmed cases of
full albinism in the dog world, though there is an If a dog has large patches of white on its face,
intermediate form of albinism that causes blue the chances for one blue eye or two blue eyes
eyes in dogs. It does not exist in purebred JRTs/ increase, as well as the chance for parts of the
Russells. nose remaining pink.

Gene mutation – a very rare gene (ALX4) that If the reader only remembers one thing about
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codes for blue eyes is mainly seen in Siberian blue eyes in JRTs, remember that it is not due
Huskies and Border Collies. It is not seen in mice to a recessive mutation that the breeder must
or humans. It is not seen in JRTs/Russells. avoid. There is no reason to place blame on
particular sires or lines. Blue eye(s) will always
Merle – Merle produces pigment dilution in a have the possibility of occurring in Jack Russells
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random pattern. This random pattern affects since they carry the white-spotting gene (Sp).
not only the coat but also the skin and eyes. All piebald dogs have the potential to have blue
The Merle gene does not exist in purebred JRTs/ eyes. To completely avoid blue eyes, the breeder
Russells. would need to switch breeds.

102 | A Worldwide Magazine for the Jack Russell Terrier / Russell Terrier • Issue 2/2023