All Collie puppies need their eyes examined by a Board Certified Canine Ophthalmologist. For us, the nearest one is Animal Eye Associates at 372 S. Milwaukee Ave. in Wheeling IL 60090 (847-215-3933). We make the six-hour trip so that we know without a doubt, the genetic components we are dealing with both in our show dogs, and the dogs we place in companion homes.
Dr Steven G. Sisler, DVM. DACVA was kind enough to take time from his busy schedule to help us in showing you some of the equipment that is needed to test the eyes. A regular vet will not have the sophisticated equipment, or the expertise to exam the Collie for the conditions that are so important to a healthy eye. You need to find a specialist with experience in Collies.
Collie Eye Anomaly (CEA) is a common term used to group several defects found in the eyes of many Collies and Border Collies, Shetland Sheepdog, Australian Shepherd and other breeds. CEA is a group of conditions which appear in conjunction with each other and are inherited as a recessive gene, but they are not necessarily simple recessives. Multiple genes, modifiers and gene series all may play a part in different expression of defects. The good news is that CEA can be diagnosed by a canine ophthalmologist as early as a few weeks old. Drops are given to dilate the pupil and the interior of the eye is examined with an ophthalmoscope. During the exam, the specialist can identify puppies affected with varying degrees of the syndrome listed below. There is no universal grading system so you will find many terms used by breeders.
Choroidal Hypoplasia, the most common term for an affected dog with only CEA present is Choroidal Hypoplasia or chorioretinal change (CRC) is the mildest form of CEA, but it is also the most complex. It is basically an area, or areas of the choroid layer which is lacking in substance to varying degrees. In its severest form of total lack of pigment tissue, the sclera is visible through the retina. The disease is bilateral, which means it affects both eyes, but not necessarily to the same degree. The disease is not progressive, unlike PRA, which means that whatever the degree of affliction, it will not deteriorate. In its mildest form, there are no symptoms apparent outside of clinical examination by a specialist, and vision is not impaired, but blindness may occur if CEA is combined with coloboma or staphyloma. This condition is further complicated when, in an attempt to produce only mildy affected CRC dogs. Mildly affected dogs can produce an eye so mildly affected that the lack of pigment can fill in and appear normal. These dogs are commonly referred to as "Go Normals" and it is virtually impossible to distinguish them from CEA clear dogs upon examination if puppies are not done early enough. For this purpose, we prefer to test prior to 6 weeks. Here is where knowledge of family history comes into play. You must always take into consideration the degree of involvement of both parents.
Mild CRC eyes show the condition upon examination with an ophthalmoscope, but are not believed to be symptomatic in the dog's eyesight, or adversely affect the eye itself. Because this mild condition is so widespread in the breed, most breeders feel this is acceptable, but are still mindful of what lies behind the condition in choosing breeding partners. By being aware of the exact degree of the syndrome their dog has, they can make educated choices to only breed those mildly affected in hopes of improving generation after generation. This is why most breeders will check every puppy in each litter with a qualified specialist.
Coloboma Is a defect of the sclera, such that a hole appears in the optic disc, or next to it. A hole in the disc itself is called a Papillary Coloboma and a hole next to the optic disc is called a Peripapillary Coloboma. A thin area or very small hole next to the optic disc will not impair vision, but obviously the larger the coloboma the more distorted vision will be and a very large coloboma will almost certainly result in a partial detachment of the retina. Detachment means a loosening or separation of the inmost, or retinal layer from the wall of the eye. This may involve a tiny area or the entire retina. The latter is termed a complete detachment, the result being partial or complete blindness in that eye. Staphyloma, while not synonymous with coloboma, still refers to holes and can affect the vision in the say way. Most Collies with colobomas do not ever reach the level of detachment and therefore do not go blind. While they should not be used for breeding, they are still lovely companion animals with no outward signs or symptoms of this problem.
There are variations even in normal eyes. These correspond somewhat to a dog's coat color. Thus it is often difficult to judge the pigment in a Blue Merle's eyes as it is diluted along with his coat color. These variations again, have no outward symptoms. It is seen only on clinical examination. It should be noted that CEA can exhibit such subtle variations that among mildly affected dogs, we find differences of opinion among experts as to which are clear or not.
Most of the specialists agree that Choroidal Hypoplasia (CEA) is carried as a recessive gene. For a dog to show clinical symptoms on examination, both parents, even if they show no physical signs themselves, must carry a gene for the condition. Evidence exists that some other parts of the syndrome are handed down differently. According to Cornell University, coloboma is not linked to CEA, but it can be masked by "normal eye/ non carriers". It is believed to be inherited independently. Staphyloma, for instance, rarely occurs except in the presence of Choroidal Hypoplasia, but coloboma can be present without CEA. Since the degree of expression is inherited without a clear pattern, it is believed that there are modifiers that are attached or present close to the CEA gene. This is currently under scrutiny by Optigen as one of many current theories, and hopefully, they will have some answers as to why this occurs soon.
OptiGen genetic lab now has a genetic test for CEA/CH which provides a powerful management tool for the breeder. This genetic test can distinguish all three genetic states normal, carrier and affected. With this information, the breeder can plan litters that avoid producing any affected dogs by always selecting one parent that is normal/non carrier. The other parent can be normal, carrier or even affected, and no affected dogs will result. There are a few breeders who judiciously select for normal eyes free of any CEA involvement at all. They have my total respect as it is not an easy undertaking. That said however, most breeders feel that mild CEA is something that we can live with in light of the many other genetic diseases we have to consider. It's non-symptomatic, detectable as puppies, and it involves about 70% of all Collies today. There are so few outstanding Show Dogs that are CEA non-carriers that finding suitable breeding partners is difficult while trying to maintain the total quality of individual lines.
The Collie Club of America encourages its members to have all their puppies checked as young as possible by a qualified specialist. Where there is none in the area, the alternative is to sell a dog contingent on a later check. No dog should be used for breeding until examined and those certificates should be available with the puppy. Any puppies offered for sale without their eye-check, are to be avoided without reservation.
PROGRESSIVE RETINAL ATROPHY unlike CEA, this disease is not widespread, but it does occur in Collies. PRA has certain features common in most breeds. Early in the disease, one of the first physical symptoms of affected dogs is night blindness. With night blindness, they are lacking the ability to adjust their vision to dim light; later their daytime vision also fails. As their vision deteriorates, affected dogs will adapt to their handicap as long as their environment remains constant, and they are not faced with situations requiring excellent vision. At the same time, the pupils of their eyes become increasingly dilated causing a noticeable "shine" to their eyes; and the lens of their eyes may become cloudy, or opaque, resulting in a cataract.
The big difference in PRA among breeds is in the age of onset and the rate of progression of the disease. Certain breeds, including the Collie, have early onset forms. In these breeds the disease results from abnormal or arrested development of the photoreceptors -- the visual cells in their retina, and affects pups very early in life. PRA can also appear much later in onset. Affected dogs appear normal when young, but develop PRA as adults. The dog has trouble seeing in dim light. An expert may detect early signs in the eye at six months or younger. With Rod Dysfunction, onset can be from birth on in early onset form and from six months to 3 years of age for late onset form, for Cone dysfunction, it can be from birth to two years for early onset forms, from six months to 5 years for late onset forms.
PRA in Collies as in all breeds so far studied is an autosomal recessive disorder. Autosomal recessive is by far the easiest to clear from a bloodline. In order to produce an affected puppy, both parents must be either carriers or affected themselves. Similarly, because affected dogs have two copies of the defective gene, all their progeny will be at least carriers. If the breeding pair are both clear, all the puppies will be clear. There is now a genetic test to detect rod-cone dysplasia type 2 (rcd2) in Collies. The rcd2 DNA test is able to identify with complete accuracy whether a dog has no copy (is Normal), has 1 copy (is a Carrier) or has 2 copies of the mutation (is Affected). The rcd2 test will not identify any other forms of PRA that may occur. At this point, researchers are not aware of other forms of PRA that occur in the collie.
Hypoplasia of the Optic Nerve is an undersized nerve which is noted where it enters the eyeball. In extreme cases, this can cause blindness.
Corneal Dystrophy is a condition which comes on when the dog is mature, often during stress. Opaque spots appear centrally on the surface of the cornea. (It is often confused by the layman with cataracts which occur in the lenses.)
Cherry Eye is very uncommon in Collies but can occur in any Breed. This refers to prolapsed gland of the third eyelid and also requires surgery to correct.
Entropion is the inward folding of an eyelid where lid hairs contact the cornea.
Ectopic Cilia is an abnormal eyelash that grows through the conjunctiva and is usually very painful and almost always causes a corneal ulcer. Distichiasis is the abnormal position of eyelashes on a lid margin that result in irritation of the eye. A skilled specialist has the equipment to 'freeze' the extra eyelashes and remove the irritation to the eye. They are not likely to come back once surgically removed in this fashion. While rare, it does occur and does have a genetic component to it.
Dermoid is another congenital defect where haired skin is located in an abnormal place on an eye and will often irritate the cornea and can cause ulcers.
Follicular Conjunctivitis is another word for itchy, reddened conjunctival tissues, tearing, squinting, often related to allergies. Puppy Pyoderma or Puppy Strangles describes eyelid abscesses associated with generalized skin pustules.
Dry Eye (Keratoconjunctivitis sicca or KCS) is a lack of or inadequate production of tears. Sometimes this can be congenital in which case it is often very serious. This is not common in Collies.
Persistent pupillary membranes (PPM) are strands of tissue in the eye present as a congenital abnormality. 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. Most of the time PPM causes no harm. Inheritance is not clearly defined, 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.
Retinal folds/ Retinal dysplasia rarely cause vision problems for the individual dog. The word "dysplasia" simply means "a defective development of an organ or structure". They represent small blind spots that cause minor vision loss. However, large areas of dysplasia may lead to large deficits in the visual field and very large retinal detachments can render dogs completely blind. Retinal dysplasia occurs when the two primitive layers of the retina do not form together properly. Mild dysplasia manifests as folds in the inner retinal layer. These are called "retinal folds". In the severe form of dysplasia, the two retinal layers do not come together at all and retinal detachment occurs. Retinal dysplasia is not progressive. It is a congenital defect and animals are born with as severe a condition as they will ever get. Retinal dysplasia can be detected as early as 6-8 weeks on an examination. The cause of retinal dysplasia in most breeds is genetic although prenatal infections with herpes virus and parvovirus may also lead to it. The mode of inheritance has not been clearly determined. Retinal folds rarely cause vision problems for the individual dog. T
Cataracts appear in different types, not all of which are hereditary. Hereditary cataracts are thought to be bilateral (both eyes), though the eyes may develop them at slightly different rates.
Non-hereditary cataracts include senile (old age) cataracts and traumatic cataracts (those caused by an injury to the eye or head.) Late-onset cataracts, which develop when an animal is 5 to 9 years of age, are probably not hereditary.
Professionals differ in their opinions of whether small opacities in the lens that do not change over time are cataracts or not. A small opacity that remains the same over 6 months to a year is probably not hereditary.
Juvenile hereditary cataracts will develop in both eyes, usually by the time the dog is two years of age. The lenses will gradually become more and more opaque until the dog's vision can be compared to looking through frosted glass--prominent contrasts in light and shadow can be distinguished and some movement noted, but all detail and subtlety of vision is lost.
In most breeds in which cataracts have been studied, the mode of inheritance appears to be complex--probably involving a number of genes. At this time there is not sufficient data to determine how hereditary juvenile cataracts are passed in dogs.
GENETIC NIGHTMARES By C.A. Sharp
Hutt, Frederick B. GENETICS FOR DOG BREEDERS, W.H. Freeman & Co., 1979.
Collie Concept by Mrs. George H. Bobbie Roos
Collie Health Foundation
iknowledgenow Veterinary Medicine Web Site!
Message from Dr. Gregory Acland from Optigen posted to ACVO Diplomate List and VOPH List
Optigen PRA genetic test