What are hyaloid arteries?
The hyaloid artery is a fetal structure that delivers blood to the area of the lens while the eye is developing. It is supposed to resolve (go away) by the time the puppy’s eyes open. Occasionally it will be noted in puppy eye exams but not in follow-up or one year exams. Sometimes all or part of it remains attached to the lens. If only a segment remains it is referred to as a remnant hyaloid. If the entire vessel is there, from the lens back to the optic disc in the back of the eye, it is a persistent hyaloid. If it is still carrying a flow of blood, it is a patent hyaloid. They may occur in one or both eyes. All types may be collectively referred to as persistent hyaloids.
How do I know my dog has hyaloid arteries?
Occasionally there will be an opacity (cataract) at the point of attachment to the pack of the lens. These may become sufficiently pronounced that you can easily see them. However, more often they are discovered during routine eye exams.
What does having hyaloid arteries mean for my dog?
In most cases they do not interfere with vision. Occasionally they will cause a cataract which may be blinding. The condition does not cause the dog any pain.
Are hyaloid arteries common in Aussies?
They are noted in about 0.5% of Aussies. This is rare, but frequent enough they bear some watching. Eye exam statistics do not indicate how many of these were in young puppies that later resolved, nor how many caused cataracts.
Are hyaloid arteries inherited?
Unknown, however individuals studying Collie Eye Anomaly, an inherited disease, have noted persistent hyaloids to be unusually frequent by in CEA carrier and affected dogs. Detailed study of this remains to be done so any association between persistent hyaloids and CEA are unclear.
What do hyaloid arteries mean for my breeding program?
Since most cases are benign in their impact on vision, it should be viewed as a potentially inherited fault. Dogs with associated cataract should not be bred. Others with persistent hyaloids might be bred, but should not be bred to other dogs with persistent hyaloid and should probably be DNA tested for CEA.