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CEA - Collie Eye Anomaly - is an inherited condition affecting the eyes of a number of breeds of dogs. Affected breeds are the Rough and Smooth Collie, the Shetland Sheepdog, the Australian Shepherd, the Border Collie, the Lancashire Heeler, and the Nova Scotia Duck Tolling Retriever.

In animals with CEA, there are abnormalities of the choroid and may also be changes in the sclera. The major change, which is present in all dogs with CEA, is 'choroidal hypoplasia', a pale patch in the back of the eye caused by abnormal development of the choroid layer. Affected dogs may also have abnormalities in the sclera, producing pits or 'colobomas' in or around the optic disk.

What does CEA mean for my dog?
In the more severely affected animals with colobomas, there is a possibility that the retina may become detached, or that there may be bleeding from the blood vessels in the eye, either of which can cause blindness in the affected eye. These complications usually occur in the first couple of years of life. Mildly affected animals with only choroidal hypoplasia appear to have normal sight. The condition in mildly affected animals does not worsen over time.

Affected: An affected dog is one who, upon dilation of the eye, shows a visible deviation from a normal or unaffected eye when viewed with the proper instruments. To be affected a dog must have inherited an affected gene from both parents. A dog can be affected in the following ways:

Vessel Tortuosity: Although originally thought to be a form of CEA, vessel tortuosity is a separate condition which may appear in conjunction with CEA. Vessel tortuosity appears in many breeds other than Collies and those affected by CEA. This condition has been traditionally referred to as a grade 1 in most eye check grading systems

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Choroidal Hypoplasia (AKA Chorioretinal Change, Choroidal Dysplasia or Choroidal Hypopigmentation): this is visible as pale areas on the fundus or as areas where the cells of the tapetum are abnormally developed or missing; fewer blood vessels exist in the choriod and pigmentation is diminished. This condition does not affect the dog's ability to see. This condition has been traditionally referred to as a grade 2 in most eye check grading systems.

Coloboma, Staphyloma or Ectasia: The coloboma is a problem that begins during embryonic development, in which the choroidal fissure, an opening in the eye tissue through which blood vessels grow, fails to close, causing the area in or around the optic nerve to remain underdeveloped. Colobomas usually appear as a hole or indentation near the optic nerve. Viewed with a microscope, it can be observed that the sclera is thin and the tapetum, choroid, and retina may be abnormally formed or entirely absent. Staphylomas are similar to colobomas but occur elsewhere on the fundus. These can be visualized as soft spots in an inflated balloon. Colobomas and staphylomas create blank spots in the dogs vision, spots where they cannot see as well. These conditions can occur in conjunction with choridal hypoplasia. Choridal Hypoplasia and Staphyloma are not progressive. What the dog displays at 6 weeks is what he/she will have for life. Colobomas can lead to retinal detachment. Staphyloma's have traditionaly refered to as a grade 3 in most eye check grading systems and Coloboma's have been referred to as grade 4's.

Retinal Detachment: a dog with a detached retina will be blind in that eye. This condition has been traditionally referred to as a grade 5 in most eye check grading systems.

Normal eyed: A normal eyed dog is a dog who, when examined by a veterinary ophthalmologist displays no visible signs of CEA, but possesses only one normal gene; the other gene is affected.

Non-carrier: A non-carrier is a normal eyed collie who possesses, or carries no affected genes. He therefore cannot produce anything but normal eyed collies.

What You Can Expect from Breeding An ...

Affected to Affected: All affected pups. Both parents have only affected genes and can therefore only pass on affected genes.

Affected to Normal Eyed: should produce 50% normal eyed carriers and 50% affected. Only one gene is required to be normal eyed, the normal eyed parent should produce the normal eyed gene 50% of the time.

Normal Eyed to Normal Eyed: should produce normal eyed non-carriers, normal eyed carriers and affected dogs. It is interesting to note that breeders have found that the percentage of affected dogs, which should be equal to that of non-carriers, out weighs that of non-carriers and of normal eyed dogs. Very few non-carriers have ever come from normal to normal breeding's. Normal eyed dogs which have a non-carrier in their immediate background appear to produce a greater percentage of non-carriers.

Non-Carrier to Normal Eyed: Should produce 50% normal eyes and 50% normal eyed non-carriers. Again it only requires one affected gene to be a carrier, and the normal eyed parent should produce the normal eyed gene 50% of the time. Unfortunately there has not been enough non-carrier to normal eyed breeding's to establish whether or not this is how it is actually working.
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Non-Carrier to Non-Carrier: can only produce non-carriers. A dog cannot pass on a gene it doesn't have.

Much confusion has historically been present, and is still present in the collie world, due to the lack of uniformity in grading systems. The advent of the CERF form with its diagnostic terms rather than a numerical grading system, is helping to clear up some of the problems with credibility of eye checks.

How Do You Know If A Dog Is A Non-Carrier?:

A non-carrier cannot be diagnosed by an eye check, as we are dealing with genes not effects of genes. Obviously if a dog comes from two non-carrier parents, he is a non-carrier. Otherwise whether or not a dog is a non-carrier can only be defined by breeding. If a dog produces a significant number of puppies, bred to an affected or normal eyed stud or bitch, and all have normal eyes, no matter what the eye check of the other parent is, it's a safe bet he/she is a non-carrier

A genetic test for CEA has recently become available, and can be used to determine the genetic status of clinically normal dogs. There is limited value in testing affected dogs, as their genetic status can be inferred. The test is offered by OptiGen and details about the test can be found on their website www.optigen.com/opt9_test_cea_ch.html; the testing itself can be arranged through your veterinary surgeon, as it requires a blood sample.

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Examination of the eye by a veterinary ophthalmologist is the way CEA is primarily diagnosed. With an ophthalmoscope, the back of the eye (the 'fundus') will be examined, and the ophthalmologist will identify pale areas of choroidal hypoplasia, and the presence of any colobomas.

However, there is a feature of CEA known as the 'go normal' phenomenon, where the changes of CEA which are present in the young puppy are masked by later development in the eye as the puppy grows, so that a puppy which would have been diagnosed as affected at a young age appears normal when examined as an adult. These animals are still affected and still carry the genes for the condition. Because of this, it is important to screen litters before the age of eight weeks in order to get a clear diagnosis. Litter screening is an important part of any control programme for CEA, and responsible breeders will have this performed

Control
CEA poses a number of problems as regards eradication and control. The 'go-normal' phenomenon, where the changes of mild CEA are masked in the adult dog by pigmentation of the eye, can lead to affected adult dogs being passed as normal on eye examination. For this reason, the best way of making a good diagnosis is eye examination of pups between 5 and 12 weeks of age, before this pigmentation takes place. Litter screening is an important part of any control programme.
DNA testing is now available, and identifies the gene for choroidal hypoplasia, which causes the pale patch in the back of the eyes of CEA affected dogs. This has a useful role in confirming a diagnosis of CEA based on ophthalmological examination, and can distinguish between genetically clear and carrier animals, which both have normal eyes on examination. These animals could only previously be distinguished by test matings (see Genetics for more details).

The reason some animals show more severe signs of CEA than others is not well understood, but is probably due to the severely affected dogs carrying other genes which, in combination with the gene for CEA, produce colobomas, which can in turn lead to retinal detachments and haemorrhages and can lead to blindness. Although it would appear that breeding from mildly affected dogs tends to produce mildly affected pups, this is by no means guaranteed, and pups with mildly affected sire and dam can show the full range of severity of the condition.

Based on this result, it is difficult to recommend this as a breeding strategy, since continuing to breed from affected animals will only increase the proportion of carrier and affected animals in the population.

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NOTE From Breeder

What are persistent pupillary membranes (PPM)?

Persistent pupillary membranes are strands of tissue in the eye. They are remnants of blood vessels which supplied nutrients to the developing lens of the eye before birth. Normally these strands are gone by 4 or 5 weeks of age. Depending upon the location and extent of these strands, they may interfere with vision. They may bridge from iris to iris across the pupil, iris to cornea (may cause corneal opacities), or iris to lens (may cause cataracts), or they may form sheets of tissue in the anterior chamber of the eye. In many dogs these tissue remnants cause no problems. How are persistent pupillary membranes inherited?Inheritance is not defined. What breeds are affected by persistent pupillary membranes?PPM are known or strongly suspected to be inherited in the basenji, Pembroke and Cardigan Welsh corgi, mastiff, and chow chow. This problem is particularly significant in the basenji where the strands often bridge to the cornea, causing opacities which may impair sight. In the basenji the condition has been seen with optic nerve coloboma - a cavity in the optic nerve which, if large, causes blindness. PPM are also seen in many other breeds, including the Akita, Alaskan malamute, American and English cocker spaniel, Australian shepherd, basset Griffin vendeen (petite), beagle, bearded collie, Belgian sheepdog, Belgian tervuren, Bichon frise, Bouviers des Flandres, Chesapeake Bay retriever, collie (rough and smooth), Doberman pinscher, English springer spaniel, golden retriever, Gordon setter, Havenese, Irish setter, Labrador retriever, Lakeland terrier, Lowchen, miniature bull terrier, Norwegian elkhound, Nova Scotia duck tolling retriever, Old English sheepdog, papillon, poodle (all sizes), Portuguese water dog, samoyed, Scottish terrier, Shetland sheepdog, soft-coated wheaten terrier, Tibetan terrier, Welsh springer spaniel, West Highland white terrier, Yorkshire terrier.For many breeds and many disorders, the studies to determine the mode of inheritance or the frequency in the breed have not been carried out, or are inconclusive. We have listed breeds for which there is a consensus among those investigating in this field and among veterinary practitioners, that the condition is significant in this breed. What do persistent pupillary membranes mean to your dog & you?Generally persistent pupillary membranes cause no problems. However if attached to the cornea or lens, the strands can cause opacities which may interfere with vision. The cataracts that can occur with PPM usually don't Worsen.How are persistent pupillary membranes diagnosed?PPM are seen in young dogs. You or your veterinarian may notice small white spots in your dog's eyes, or you may suspect that your dog's vision is impaired if the condition is severe. With an ophthalmoscope, your veterinarian will be able to see the membranous strands, and whether they adhere to the lens or cornea. How are persistent pupillary membranes treated?There is no treatment for the membranes themselves and in most cases there are no associated problems. If there is significant edema or "bluing" of the cornea due to adhesions, hyperosmotic eyedrops may help. Surgery may be required if there are extensive cataracts.Breeding adviceThis is a particularly common defect in basenjis. Affected dogs and their close relatives should not be used for breeding. Ideally, all basenjis, even those not obviously affected, should have careful ophthalmic examinations for PPM before their use in a breeding programme.The defect is also significant in Welsh corgis (Pembroke and Cardigan), chow chows, and mastiffs. Affected dogs and their close relatives should not be used for breeding.In other breeds, parents and siblings of affected dogs should be examined ophthalmoscopically. If close relatives are affected, breeding is discouraged. Where PPM appears to be an isolated incident, breeders may use their discretion. We retest ALL our breeding dogs at a later time for many disorders develope later like

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DISTICHIASIS AND DOGS

Distichiasis is the abnormal growth of an eyelash or several extra eyelashes. This congenital disease affects the meibomian glands along the eyelid. In some dogs, the position of the eyelash has not effect on the dog and it is likely to go unnoticed. However, if the eyelash makes direct contact with the surface of the eye, the eye may suffer from microscopic scratches and irritation. Over time, these scratches can become infected and may predispose your dog into developing a corneal ulcer. Breeds of dogs which have a high incidence of distichiasis include, cocker spaniels, chesapeake by retrievers, lhasa apsos, miniature poodles, golden retrievers, shelties and shih tzus.Distichiasis is also commonly associated with tearing of the eye, squinting or a painful eye, visible scratches or white spots on the surface of the eye as well as eyelid spasms. Dogs who are showing signs of distichiasis are usually taken to their veterinarian when an eye infection is suspected. Although these dogs respond well to treatment, the infections may recur and the offending eyelash may remain hidden under the eyelid. An ophthalmic examination is often needed to reveal the eyelash, although this examination may require sedation.

The permanent treatment of distichiasis requires the removal of the offending eyelash or eyelashes. Plucking the eyelash will only result in regrowth, so other methods should be considered. Cryosurgery, or the freezing of the lid margin, can be used to prevent hair regrowth as can other surgical procedures. The surgical procedure your veterinarian proposes will be determined by the number of eyelashes and the state of the lids themselves. In some severe cases, your veterinarian may refer you to a veterinary opthalamologist for treatment.. Note very seldome can this be detected in a young collie puppy therefor this disorder may should be looked for at a later age in collies . Over 6 months of age is good

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