It does not impact vision but should be considered faulty for breeding purposes. Whether it is a milder expression of the same process that produces IC ic not known. Some dogs are diagnosed with iris hypoplasia. Normal dogs which produce IC should be bred to mates with little or no family history of IC. It is very possible that non-merles with normal irises might carry the genes. The reason for the high association with merles is not known. Almost all iris colobomas in Aussies were seen in merle dogs, however they will occasionally be found in non-merles. The mode of inheritance for iris coloboma is unknown. The American College of Veterinary Ophthalmologists (ACVO) recommends that Australian Shepherds’ irises be examined prior to dilation. Late-stage syphilis is the main cause of AR pupil. It is most commonly present in both eyes (bilateral) but can, in rare cases, affect only one eye (unilateral). Some small colobomas may not be apparent when the eye is dilated and thus missed. AR pupil is also characterized by small, misshapen pupils. If the dog is being presented to a veterinary ophthalmologist the irises must be examined before dilation. Iris colobomas are generally detected during an ophthalmologic exam, but some may be noted by small animal veterinarians or noticed by the owner. This can cause minor discomfort as well as temporarily reducing the range of vision, which could impact performance or work. Chemical trauma is caused by cleaning supplies, pool supplies, pepper spray, mace or. However a large coloboma can force a dog to squint in bright light because the iris is incapable of contracting properly to reduce the amount of light entering the eye. Misshapen iris or pupil Loss of intraocular pressure. This condition is present at birth and in most cases the effect on vision is minimal. Colobomas may be only small notches out of the inner edge of the iris, pie slices, or massive holes – occasionally so large it appears the dog has no iris at all.

Iris coloboma occurs when part of the iris fails to develop.

Misshapen pupil