Double merles! Who in the right mind would breed double merles?
Double Merles will have hearing deficiencies. As with Pattern White pups, if the excess white does not affect inner ear pigmentationG, they will be able to hear, or have only minimal hearing loss (or possibly only in one ear). It is not possible to tell if a Double Merle dog is deaf by looking at any visible hair on the ears (look through our Pictures page for examples). An interesting article is at Clan Duncan Shelties Growl Pages - Seeing Double.
Double Merle dogs may also have a variety of eye defects that can occur in any color eye (see Double Merle Eyes for some pictures), referred to as "Merle Ocular Dysgenesis." Many dogs will have multiple eye defects, and most of those will have some vision loss, sometimes to the point of blindness. Visible eye defects are often the easiest way to determine whether a dog is a Pattern White or a Double Merle.
Visible Eye Defects in Double MerlesThe pupil may have spiky projections (called "starburst") or jagged/irregular edges (called "eccentric"). This is not the same as a colobomaG, which can occur in the eye of a dog (or human) of any color or pattern. This can make the eye very light sensitive if the pupil doesn't react as well as it should.
Invisible" Eye Defects in Double Merles Double merle dogs are more likely to have defects within their eyes, which will require an exam by a veterinary ophthalmologist for proper diagnosis. None of these conditions are exclusive to double merles.
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