What You Should Know About Collie Eye Anomaly

Collie eye anomaly (CEA) is a genetic condition where the eye does not develop normally in the fetus.

This disease is strongly linked to collie breeds such as rough collies, Shetland sheepdogs, Border Collies, smooth collies and Australian Shepherds. Of those dogs who have CEA, around 25% have seriously impaired vision or are blind.

Although there is no cure or treatment, the good news is that genetic screening tests are now available. Through responsible breeding, this disease should become increasingly rare.

Symptoms

A newborn puppy’s eyes open around 7–10 days old. While some puppies with CEA are only mildly affected, others may be blind, even within the same litter. Indeed, the same puppy may have different lesions in each eye.

The signs of CEA are those associated with poor sight such as bumping into objects and locating food by smell rather than sight. A blind puppy will not blink when a finger is waved close to the eyeball, and bumps into objects in a room he is not used to.

Happily, this condition does not deteriorate -- with 1 important exception -- and so the eyesight the puppy has at 12 weeks old remains with him for life.

The exception is dogs who develop retinal detachment, which can happen suddenly at any age. Coloboma, one of the defects associated with CEA, weakens the retina’s attachment to the back of the eye, causing the retina to peel away, resulting in blindness.

Causes

If the mother and father both carry the CEA gene (an autosomal recessive trait), then their puppies most likely will have the condition.

If only 1 parent has the faulty gene, the puppies are not affected, but are carriers. If they are mated to another carrier, their offspring will have CEA.

The physical defects in the eye are caused by improper development of the fetal eye when the pup is in the womb.

The anomalies that give this condition its name refer to 3 things:

1. Choroidal hypoplasia. The choroid is the layer on top of which the retina rests. A normal choroid is dark-colored and stops light reflection within the eye. It also carries the blood vessels that nourish the retina. An underdeveloped choroid looks more like a pane of glass than a blackout curtain, and because of the lack of blood vessels, the retina is starved of oxygen and cannot work properly.
2. This is the equivalent of having a pit at the back of the eye instead of a flat surface.
3. Retinal detachment. If a coloboma is present, it’s a bit like not stitching the seams of a garment, and the retina can lift away from the back of the eye.

Diagnosis

In the hands of a skilled veterinary ophthalmologist, a diagnosis can be made in puppies as young as 5–8 weeks of age. The specialist inspects the eye with an ophthalmoscope and looks for thinning of the choroid, lack of pigment and blood vessels disappearing into the pit of a coloboma.

A more reliable test, especially in adult animals, is a screening genetic blood test. This involves the veterinarian taking a small sample of blood and sending it off to a special lab.

This genetic test can pick up all 3 states: affected, carrier and normal. It gives invaluable information about which animals are safe to breed from.

Treatment

There is no treatment for collie eye anomaly. Responsible breedingis the only thing that can eliminate this condition in the future.

Prevention

The health of future generations of collies lies squarely in the hands of dog breeders. With reliable genetic tests available, there is no reason for a breeder not to screen his animals and only breed from those who test negative.

Unfortunately, with up to 90% of breeding stock either being carriers or affected, many breeders are unwilling to test their dogs and risk being unable to use valuable stock. Ultimately, this condition will only be taken seriously when people refuse to buy puppies from unscreened parents.

Reference

• Small Animal Ophthalmology. Pfeiffer & Peterson-Jones. Publisher: WB Saunders. 3rd edition.

This pet health content was written by a veterinarian, Dr. Pippa Elliott, BVMS, MRCVS. It was last reviewed Nov. 2, 2018.