Eyes FAQs

 

What are cataracts?

A cataract is an opacity of the lens, which sits just behind the pupil in the eye.  Most hereditary cataracts in Aussies arise in the center of the back of the lens, referred to as posterior polar.  Aussie hereditary cataracts almost never occur in young puppies; affected dogs most commonly present signs as mature adults, though cataracts may start in early adulthood or not until old age.  Cataracts can occur for reasons other than heredity (other diseases, injury, or nutritional imbalance) but these other causes are not common and should not be assumed to be the reason unless confirmed by a veterinary ophthalmologist.

How do I know if my dog has cataracts

Very advanced cataracts can be seen without magnification.  The pupils will be somewhat dilated and appear milky white.  However, most cataracts are detected during exam.  Hereditary cataracts are bilateral, meaning they occur in both eyes, but they may not appear at the same time.  If a cataract is noted on one eye, it is wise to recheck in six months to a year to see if one develops in the other.

What does having cataracts mean for my dog?

Hereditary cataracts progress starting as small opacities and advancing, sometimes to the point of clouding the entire lens.  Dogs with these generalized cataracts are unable to distinguish anything but extremes of light and dark.  Cataracts do not cause the dog any pain and usually progress slowly enough that the dog adjusts to its vision loss.   Some dogs progress very slowly and have functional vision throughout their lives.  Cataract surgery can be performed, but it is expensive and not always successful.

How common are cataracts in Aussies?

Roughly 4% of Aussies will develop cataracts.  They are the most common eye disease in the breed.

Are cataracats inherited in Aussies?

In most cases.  The mode of inheritance for most Aussie cataracts is dominant with incomplete penetrance, meaning not every dog with the mutation will develop cataracts though 70% of those with cataracts have it.  The remaining hereditary cataracts are caused by as yet (2013) unidentified genes.

Is there a DNA test for cataracts?

Yes.  There is a test for a dominant mutation of a gene called HSF4.  This mutation is extremely common in the breed:  Approximately one in four Aussies has it.  Dogs with two normal copies of the gene will not develop this type of cataract.  Dogs with one or two copies of the mutation have a heightened risk for developing cataracts.

What do cataracts mean for my breeding program?

Because the HSF4 mutation is only a risk factor and because there are hereditary cataracts that are not caused by HSF4, all breeding stock should receive annual exams by a veterinary ophthalmologist.  Because the HSF4 mutation is so common, eliminating all dogs that have it from breeding is not an option.  Affected dogs should not be bred; if semen has been stored from males that develop hereditary cataracts it should be discarded.  Normal dogs with the mutation should be bred only to clear-tested dogs and preference given to clear-tested offspring to carry on with.  Relatives of affected dogs whose cataracts were not due to HSF4 or for which HSF4 status is unknown should be bred to clear mates with no recent family history of non-HSF4 cataracts or cataracts not clearly known to be HSF4.

Do dogs that are blind from cataracts need to be put down?

Absolutely not!  Most blind dogs cope very well.    Use your own eyes to watch out for dangers he will not perceive.  Blind dogs memorize their home turf.  If you move furniture or other large objects in the house or yard, you need to show your dog what you changed by taking him to the new or newly positioned object.  Never let him wander off lead in an unfenced area.  Keep an eye out for traffic, obstacles or other animals and things that he might blunder into.  If you haven’t already, get some basic obedience training on him.  Especially a rock-solid “freeze” command of some sort.  This could be “down,”  “sit,” or whatever.  Just have a way to make sure the dog will stop in his tracks if necessary.  Dogs depend on hearing and olfaction much more than on eyesight and most will adapt very well to their new circumstances.

I know someone whose dog was diagnosed with punctate cataracts but it passed its eye exam.  How can a dog with cataracts pass?

Punctate cataracts are very small and may not be inherited.  Lens opacities occur for a variety of reasons, not all of them genetic.  Our typical hereditary cataract is in the posterior cortex (back side of the lens in the outer layer of tissue.) It will be bilateral, though both eyes may not start to show them at the same time.  The cataracts will advance over time.  They usually begin between 2-5 years of age, but may start earlier or later.

A dog with posterior punctate cataracts might be in the early stages of hereditary disease and should have the DNA test for the HSF4 cataract mutation.  If it is clear for HSF4, re-check it after 6 months to a year to see if the cataracts had advanced.  If they have not, the opacities were probably non-hereditary.

Are nuclear cataracts inherited?

Probably not.  Aussie inherited cataracts are usually in the cortex (outer layer of the lens) and on the back side.  Nuclear cataracts are probably caused by something else—injury, disease, or environmental factors. The appearance and location of acquired cataracts is usually different from the inherited kind.  A veterinary ophthalmologist should be able to tell.

One of my puppies failed its eye exam because of a cataract on the suture lines in one eye.  What are these and what does this mean for the rest of the litter?

It may not mean much at all.  Puppy cataracts are extremely unusual in this breed are not likely to be inherited.  The suture lines are on the back and front of the lens where the lens tissue joins during development.  Minor suture line opacities aren’t considered to be inherited.  Inherited cataracts typically occur in both eyes; at present this is not the case with your puppy.  Is this cataract associated with a hyaloid artery?  Sometimes these structures will cause a cataract at the point of attachment.  Persistent hyaloid arteries do appear to be inherited, but most are not associated with cataracts.

You should consider doing the following:

  1. Get a second opinion.
  2. If the second vet also finds a cataract, wait a six months to a year and have the puppy rechecked.
  3. In the meantime, get it HSF4 tested.  The lab will do this for free if you provide a copy of the CERF report showing the cataract and a pedigree.
  4. If cataract is still there at the time of the recheck, don’t breed the dog or repeat the breeding just to play safe.

If the dog is clear from HSF4 and/or it passes the second opinion or recheck at a year, don’t worry about the littermates.  If it is found to have even one copy of the HSF4 mutation, the parents and littermates need to be tested to determine their status.

Are merles more likely to develop cataracts?

No more likely than tris!  There has been no evidence that cataracts correlate with coat color in any breed of dog.  In the case of Aussies, most (but not all) of our inherited cataracts are due to the HSF4 gene which has shown no evidence that it is linked to any coat color genes.   Cataracts are an extremely common canine eye disease and occur in many other breeds, most of which do not have merle.  It is probable that the genes causing non-HSF4 cataracts in Aussies aren’t linked to color either.

That said cataracts can be secondary to some other eye diseases and defects.  Homozygous merles often develop cataracts but it isn’t specifically because they are merle.  It happens because of the things that have gone wrong in the eye.

What is Collie Eye Anomaly (CEA)?

CEA is a disease of the vascular and nerve tissues in the back of the eye.  The most common defect is choroidal hypoplasia (CH), also called chorioretinal dysplasia, a thinning of the vascular tissue that lies between the retina and the wall of the eyeball.  Every dog with CEA has CH in both eyes.  Some dogs also have optic nerve coloboma in which a portion of the optic nerve where it enters the back of the eyeball has failed to develop.  Another less common CEA defect is retinal detachment.

How do I know if my dog has CEA?

In most cases you won’t know without an exam by a veterinary ophthalmologist, though occasionally a puppy will be blind.

Why do you have to check every produced and do it at such a young age?

CEA can be tricky to catch.  If you don’t check all the puppies in every litter, you may miss the affected ones.  If they aren’t checked young, they may become masked affecteds (once referred to as “go normals”) and be indistinguishable from unaffected dogs.  If a puppy is a double merle you won’t know because the eye defects typical in dogs that inherit two copies of the merle gene will make it impossible to recognize CEA for what it is.  Ideally, puppy exams should be done before 6 weeks of age to be sure they are checked before any might become masked affecteds.

What is a masked affected?

A dog that has CEA that can’t be detected in an eye exam is a masked affected.  These dogs do have the disease; they just can’t be diagnosed by eye exam.  If a dog has only choroidal hypoplasia sometimes the natural pigment in the back of the eye hides its presence.  The pigment is not present in young puppies but starts to fill in at about 6 weeks.

What does having CEA mean for my dog?

CEA causes no pain or discomfort, but it can impact vision.  Most dogs with CEA have only choroidal hypoplasia and their vision is functional.  Optic nerve coloboma can reduce vision and very large colobomas can leave the dog blind in the affected eye.  Detached retinas are also blinding.   Dogs that are blind in one eye can function well but can be at risk from hazards that arise on their blind side; activities like agility and stockwork may be ill advised.  If a dog is totally blind it can live a good life though certain activities won’t be possible and it will need to be protected from hazards it cannot see.  The senses of smell and hearing are more important to a dog than vision and most dogs adjust well, particularly those blind from birth as would be the case if the dog had CEA.

Is CEA inherited?

Yes, the gene which causes choroidal hypoplasia has been located and the mutation is recessive.  Since all dogs with CEA have CH it can be managed in the same way one would manage any single gene recessive trait even though other as-yet unidentified genes cause the more serious defects.

How common is CEA in Aussies?

Fewer than 1% are affected.  It is likely that somewhere between 5 and 10% are carriers.

How likely is it that a normal littermate to a puppy with CEA carries the gene?

Every normal full sibling of a dog with CEA has a 2 in 3 chance of being a carrier. 

Is there a DNA test for CEA?

Yes.  It tests for the gene mutation that causes choroidal hypoplasia which is present in all CEA dogs.  Results will indicate whether your dog has one, two, or no copies of the mutated version of the CEA-CH gene  Dogs with two copies are affected whether or not the have clear eye exams (see the question about masked affected dogs above).  Dogs with one copy of the mutation are carriers.  If your dog does not have the mutation it is clear of CEA.

What dogs should be tested?

Any Aussie that is thought to be affected with CEA should have the test to confirm the diagnosis.  Optigen will waive the fee if you present a copy of the eye exam results and a pedigree along with the DNA sample (contact them ahead of time to make arrangements.)  First-step relatives (parents, full and half siblings, and offspring if any) of affected dogs who will be used for breeding should be tested.  Parents, full siblings, and offspring of a CEA carrier should be tested When it is determined which parent of a DNA tested carrier is the source of the mutation the half-siblings through that parent should also be tested.  There is no need to test dogs whose parents have both tested clear.

What does CEA mean for my breeding program?

With the DNA test CEA can easily be managed in your breeding program without fear of producing more affected pups.  Do not breed affected dogs and breed carriers only to clear-tested mates.  Give preference to clear-tested offspring to carry on with.  No male that is a CEA carrier should be used extensively at stud.

What is distichiasis?

Distichiasis is presence of an abnormally positioned eyelash.  These can arise any time in a dog’s life.  They may come and go.  If the lash grows toward the cornea it may cause abrasion to the corneal surface.  This can be quite painful and may result in permanent scaring if not treated. Minor distichia will pass the eye exam though the examiner will note them.

 How common is distichiasis in Aussies?

About 1.5% of the Aussies have distichiasis.

 Is distichiasis inherited?

Yes, though the details of how it is inherited are not known.  Distichia should be considered faulty with the degree of fault increasing with the number of lashes or repeat incidents (i.e. new ones keep cropping up.)  Minor distichia are not, by themselves, a reason not to breed if the dog is otherwise good to excellent.  Just be sure to avoid mates that have or have had distichiasis themselves or who have a family history for it.  If a dog had distichia which required surgery or caused corneal damage it should not be bred.  Breed its near relatives carefully, as outlined for a dog with minor distichia.

What is iris coloboma?

A coloboma is any area of eye tissue that fails to develop.   A dog could have a coloboma of the iris, the optic nerve, the lens, or even an eyelid.   If your dog is diagnosed with a coloboma, it’s important to know what specific tissue was involved.  Whatever kind it is, an affected dog should not be bred.  However, some types of coloboma are more serious than others for both dog and breeder.  The defect has only a small effect on the dog’s vision. A large coloboma of the iris can inhibit its natural contraction in response to bright light, causing the dog to squint the affected eye.  But if the coloboma is small, it will pose little difficulty for your dog.

How can I find out if my dog has iris coloboma?

Some iris colobomas are easy to see.  However, if only a small piece is missing you may not be able to.  They can be especially difficult to see in young puppies and dogs with eyes that combine blue and pigmented areas.  Pigment variation may appear to be a coloboma to the naked eye.  If you think your dog may have an iris coloboma, get it examined by a veterinary ophthalmologist.  If you go to an eye exam clinic, make sure your dog is examined before the eyes are dilated; small colobomas can be missed in dilated eyes.

Can a dog develop iris coloboma later in life?

No.  If a dog has had clear eye exams and later is found to have iris coloboma it was missed on the earlier exams.  The American College of Veterinary Ophthalmologists recommend that all Aussies should have the irises examined prior to dilation to prevent this from happening.

What does it mean for my dog if it has iris coloboma?

In most cases an iris coloboma has little if any effect on vision.  Iris coloboma does not require medication or surgery.  If the coloboma is large enough to cause the dog to squint in bright light there may be some discomfort connected to the light sensitivity.  A dog with an iris coloboma this large may misjudge distances.  If a dog is competing in high-speed sports like agility or one that is doing stockwork, whether for trials or real farm/ranch work a larger iris coloboma could be hazardous when the dog  is negotiating obstacles at high speed or dodging flying hooves.

How common is iris coloboma in Aussies?

About one Aussie in seven has it.

 Does merle-to-merle breeding cause iris coloboma?

No.  This misconception may have arisen because they are most frequently seen in merles and double merles often have abnormal irises along with the other eye defects typical of dogs that inherit two copies of the merle gene.

Can iris coloboma cause glaucoma?

No.  It is not associated with glaucoma, which is extremely rare in Aussies.

Is iris coloboma inherited?

Yes, though the specifics of how it is inherited are not yet known.  Merles are more likely to be affected but it is not caused by the merle gene.  However, merle may be a risk factor when combined with whatever other gene(s) underlie the defect.

What does iris coloboma mean to my breeding program?

Dogs with iris coloboma should not be bred.  The parents and full and half siblings of an affected dog should not be bred close on the pedigree that produced it and should be bred to mates that do not have a family history of iris coloboma.

What is iris hypoplasia?

Iris hypoplasia is thin iris tissue.  This is a developmental issue and may have some relation to iris coloboma, in which some portion of the iris fails to develop at all.  However, this is not established at this time.

How can I find out if my dog has iris hypoplasia?

Have the dog examined by a veterinary ophthalmologist.  Dogs with iris hypoplasia will pass an eye exam.  It is not always noted by the examiner and if it is very minor it might be missed.  If a dog has had clear exams with no mention of iris hypoplasia and later is found to have it, the condition either was missed nor not recorded in the prior exams.

What does it mean for my dog if it has iris hypoplasia?

Iris hypoplasia will not affect your dog’s vision.

How common is iris hypoplasia in Aussies?

About one percent have it.

Is iris hypoplalsia inherited?

Unknown.  However, if it does prove to be a mild form of the same process that causes iris coloboma then it would be inherited.

What does iris hypoplasia mean for my breeding program?

No dog worthy of breeding should be removed from a breeding program because of iris hypoplasia.  If you want to err on the side of extra caution, don’t breed it to another dog with iris hypoplasia nor to dogs with a family history of iris coloboma.

What is persistent pupillary membrane (PPM)?

The pupilary membrane is a fetal structure which covers the pupil prior to birth.  Sometimes all or part of it fails to go away, or “persists.”  This can occur in one or both eyes.  The PPM is made up of iris tissue but sometimes parts of it will attach to the cornea, the clear covering over the front of the eye, or the lens.  Most dogs with PPM have functional vision but occasionally there will be moderate to severe vision loss in the affected eye.

How do I know if my dog has PPM?

Sometimes it is possible to see PPM yourself, but it is best to have this confirmed by a veterinary ophthalmologist.  Since the condition is present from birth it should be noted the first time the dog is examined.  If a dog had a clear report and is later found to have PPM, get an additional opinion because someone was mistaken.

Can PPM go away?

Yes.  PPM is a developmental error.  The pupilary membrane is supposed to go away.  Sometimes this process is delayed and a PPM found in a young puppy will be gone by the time it is 6 months old.  These are not a problem.

Why is iris-to-iris PPM OK when other kinds aren’t?

The American College of Veterinary Ophthalmologists does not consider iris-to-iris PPM to be significant because it does not cause visual problems for the affected dog.  Some PPMs attach to the lens or the cornea where they may cause blinding opacities.  Iris sheets may block a significant portion of the pupil, preventing the dog from seeing with the affected eye.  This is why iris-to-iris will pass (usually with a notation) but the other types will not.

What do I do if my dog has PPM?

If your dog is diagnosed as a young puppy, the PPM may go away.  You should be able to find out by the time the dog is 6 months old.  If it persists beyond that point it will be there for life.  PPM does not cause your dog any pain.  In most cases it does not cause any significant visual problem.   Dogs with iris-to-iris PPM can do anything a normal dog might do.  However, if the PPM is of a type that does limit vision you need to take that into consideration when deciding what kind of activities you want your dog to participate in.

Is PPM inherited?

Yes, though the specifics of inheritance are not yet known.

How common is PPM in Aussies?

This is a common eye defect in Aussies, but the more serious forms are very rare.

What does PPM mean for my breeding program?

Dogs with the more serious forms of PPM (iris sheets or attachments to cornea or lens) should not be bred.  Dogs with iris-to-iris PPM may be bred but to be safe it would be best not to breed to another dog with PPM or to mates with a family history of PPM.  Don’t repeat a breeding that produces the more serious types of PPM.  Parents and normal-eyed full and half siblings may be bred but try to avoid mates with PPM or from families that have a history of PPM.

What is progressive retinal atrophy?

Progressive retinal atrophy (PRA) is a group of eye diseases featuring the gradual degeneration of the retina.  Each type has a different genetic cause.  Aussies are known to have a form of PRA called progressive rod cone degeneration (prcd.)

What is progressive rod cone degeneration (PRCD)?

It is the most common form of PRA in dogs and is the only one found in Aussies, though rare in the breed.  PRCD causes the gradual degeneration of the rods and cones, the sensory cells lining the back of the eye.  PRCD arises in mature adults.  The first sign you notice may be night blindness but over time the dog will eventually lose all its vision.  Both eyes will be affected.

How can I tell if my dog has PRCD?

If your dog seems to be having trouble seeing things at night or in low light levels, get it to a veterinary ophthalmologist for an exam.  The vet will dilate the eyes and inspect the retina.  PRCD may require more than one exam spaced a few months or more apart to make a diagnosis.  If PRCD is suspected there is a DNA test that can confirm the diagnosis.

What does PRCD mean for my dog?

Unfortunately, there is no treatment and your dog will gradually go blind.  Most dogs adjust very well to loss of vision.  A dog’s senses of smell and hearing are more important to the way it perceives the world than its eyesight.  The disease does not cause the dog any pain.  You will need to keep in mind that your dog’s vision is going and take steps to protect him from dangers he might not be aware of.

How common is PRCD in Aussies?

Fewer than 1% are affected.  It is likely that somewhere between 5 and 10% are carriers.

Is PRCD inherited?

Yes.  PRCD is recessive, so a dog has to have two copies of the mutation to have the disease.  Both of its parents must have at least one copy.  Dogs with only one copy will be healthy carriers.

Is there a DNA test for PRA?

Yes.  Results will indicate whether your dog has one, two, or no copies of the mutated version of the PRCD gene.  Dogs with two copies will become affected during adulthood.  Dogs with one copy of the mutation are carriers.  If your dog does not have the mutation it is clear of PRCD.

What dogs should be tested?

Any Aussie that is thought to be affected with PRA should have the PRCD test to confirm the diagnosis.  Optigen will waive the fee if you present a copy of the eye exam results and a pedigree along with the DNA sample (contact them ahead of time to make arrangements.)  First-step relatives (parents, full and half siblings, and offspring) of affected dogs and those found to have two copies of the mutation who will be used for breeding or whose owners want to know if they will develop PRCD should be tested.  Parents and offspring, and full siblings of a dog found to have one copy of the mutation should be tested; when it is determined which parent is the source of the mutation the half-siblings through that parent should also be tested.  There is no need to test dogs whose parents have both tested clear.

Is the Optigen PRCD test 100% accurate?  Do offspring of clear tested parents also needed to be tested?

This test, like all the DNA screening tests, is extremely accurate.  However, if the sample is mislabeled or contaminated with other DNA (almost always due to errors by the person collecting the sample) you might get an inaccurate result.  However, the fault in this case is with the sample collector rather than the test.

There are several other forms of PRA caused by different genes but those have not been identified in Aussies as of this time.  If a dog out of clear-tested parents is diagnosed with PRA, the best thing to do is submit a DNA sample from the dog to Optigen along with a copy of the eye exam and copies of the parent’s PRA certificates.  (You need to contact them ahead of time to arrange this and they will not charge you for the test.)  They will screen the dog not only for prcd but the other types of PRA for which there are DNA tests as well.  Because there is more than one form of PRA, if there should happen to be a second form in the breed  and your dog had the genes for that type it would be possible to test your dog “for PRA” using the PRCD test with clear results when the dog is actually affected – but with a different form of PRA.

What does PRCD mean for my breeding program?

Affected dogs and those with two copies of the mutation it should not be bred.  Dogs with one copy may be bred but only to dogs that have tested clear and their offspring which might be bred will need to be tested so their PRCD status is known.

What are retinal folds?

Retinal folds are tiny wrinkles in the retina.  They are sometimes noted in little puppies and often go away as the puppy grows.  They do not cause any loss of vision

What do retinal folds have to do with Canine Multifocal Retinopathy (CMR)?

Retinal folds can be a sign of CMR.

What is CMR?

CMR is sometimes called retinal dysplasia.  It causes blister-like defects in the retina. CMR can be detected by 4 months of age. It may gradually progress or may go away. Diagnosis by exam can be difficult; CMR may be described as retinal dysplasia or retinal folds, both of which are reported in Aussies. In rare instances the disease can impact vision.  Some dogs with CMR may not show signs.

How do I know if my dog has retinal folds or CMR?

They can only be found with an eye exam conducted by a veterinary ophthalmologist.  If the dog has CMR the vet may note it as retinal folds or as retinal dysplasia.  ASHGI strongly recommends that if your dog is diagnosed with either retinal folds or retinal dysplasia that you have the DNA test for CMR done on the dog.  Optigen, which offers this test in the US, may do it for free if you provide a copy of the eye exam report and a pedigree along with the DNA sample.  Contact them before submitting the sample to confirm.

Will retinal folds go away?

Sometimes.  Especially in young puppies.

What does it mean for my dog if it has CMR?

Most dogs with CMR have normal vision.  A few dogs will have diminished vision due to CMR.  There is no treatment but the disease does not cause any pain.  You would need to make sure the dog is not put in situations where it might be injured or frightened by hazards it cannot see.

Is CMR hereditary?

CMR is due to a recessive gene mutation.  Affected dogs will have two copies of the mutation.  Each of an affected dog’s parents must have at least one copy.

How common is CMR in Aussies?

This hasn’t been determined.  The CMR mutation was identified in Aussies relatively recently.  It is very possible that cases of retinal folds and retinal dysplasia reported in Aussies are actually CMR then roughly 1% have CMR and around 18% more are carriers.

Is there a DNA test for CMR and what do the results mean?

If a dog with folds is a potential breeder, you might want to get it tested.  Parents and full and half siblings of dogs affected with CMR who might be bred should be tested.   Two copies of the mutation mean the dog is affected with CMR; dogs with one copy are carriers.

What does CMR mean for my breeding program?

Dogs that have diminished vision due to CMR should not be bred.  As long as vision isn’t impacted the dog may be bred.  Dogs that have one or two copies of this mutation should only be bred to dogs that have tested clear.

What is retinal dysplasia?

RD is rare in Aussies and I don’t know for sure whether the few cases that are seen are or aren’t inherited.  To be safe, I wouldn’t breed an affected dog. Some RD dogs have retinal detachment, which is blinding.  Retinal folds can be associated with retinal dysplasia.  The more serious retinal detachment can also be caused by trauma or be a sign of Collie Eye Anomaly. Detachment due to trauma requires a significant blow to the head or many blows over a period of time. (Human boxers sometimes wind up with detached retinas.)  Detachment is the worst manifestation of CEA as well as RD.  Given the rarity of RD in Aussies, if a dog is born with detached retinas it most likely has CEA.  A veterinary ophthalmologist ought to be able to tell which you are dealing with.

What is cone degeneration (CD)?

CD causes day blindness; affected dogs can’t see in bright light but have normal vision when the light level is low.

How do I know my dog has CD?

If the dog shows signs of vision loss in the daytime but not in the dark it should be checked by a veterinary ophthalmologist.  If the dog is found to have retinal degeneration the DNA test should be done to confirm the diagnosis.

What does having CD mean for my dog?

Your dog will have increasing vision loss to the point of blindness in bright light, and normal vision in very low light.  Vision will be impaired to some degree in intermediate light levels.  The disease is not painful.

How common is CD in Aussies?

Unknown but probably rare.

Is CD inherited?

Yes.  It is recessive. 

Is there a DNA test for CD?

Yes.  Dogs with two copies of the mutation are affected, dogs with one copy are carriers.  Because this disease causes blindness, parents, full siblings and offspring, if any, of affected dogs and any that are found to have even one copy of the mutation should be tested if they are used for breeding.  As additional affected or carrier dogs are identified via testing, their untested first-step relatives who are to be used for breeding should be tested.

What does CD mean for my breeding program?

Don’t breed affected dogs.  Breed carriers (parents of affected dogs or those with one mutation) only to clear-tested mates.  Preference should be given to clear-test offspring to carry on with.

What are entropion and ectropion?

Entropion is an eyelid that rolls in and ectropion is an eyelid that rolls out.  Both conditions tend to be associated with loose skin on the face.

How do I know if my dog has entropion or ectropion?

You will notice the lid(s) bending in toward the eye or curling out, exposing the pink skin inside.  Diagnosis should be confirmed by a veterinary ophthalmologist.

What does having entropion or ectropion mean for my dog?

Both can be painful to the dog.  When a dog has entropion the lashes and even hair on the lid may scrape against the cornea every time the dog blinks, abrading its surface. The exposed mucosal skin caused by ectropion can become irritated or be damaged.  In the worst cases surgery may be required to restore the lid to a natural shape.

How common are entropion and ectropion in Aussies?

Extremely rare.

Are entropion and ectropion inherited in Aussies?

These eyelid abnormalities are associated with loose facial skin.

What do entropion and ectropion mean for my breeding program?

An Aussie should have skin that is tight to the face.  Eyes should appear almond-shaped, not round, and the lids should not droop.  The lips should be smooth and tight to the mouth with no tendency to drooling or a wet face.  Loose facial skin is faulty.  Selecting for tight, “dry” faces should help prevent both ectropion and entropion.

What is PHPV/PTVL? 

The alphabet soup stands for Persistent Hyperplastic Primary Vitreous/Persistent Tunica Vasculosa Lentis.  PHPV is a congenital defect, meaning it is present at birth.  It is due to abnormalities in the development and regression of the hyaloid artery.  The hyaloid is a fetal structure that is necessary before birth for proper development of the lens.  It is supposed to go away around the time the pup is born.  Occasionally it fails to do so, at least in part, and is then called a hyaloid remnant.

PHPV abnormalities involve the back of the lens and sometimes include Persistent Tunica Vasculosa Lentis (PTVL), the failure of vascular tissue on the back of the lens (originally connected to the hyaloid) to go away.  The correlation between PHPV/PTVL and hyaloid remnants is not known.

How do I know if my dog has PHPV/PTVL?

It will be noted on an eye exam.

What does having PHPV/PTVL mean for my dog?

PHPV/PTVL can cause visual impairment and is sometimes associated with other eye defects.

Is PHPV/PTVL common in Aussies?

It is very rare.

Is PHPV/PTVL inherited in Aussies?

PHPV/PTVL is recognized as inherited in some breeds (Bouviers, Dobermans, Staffordshire Bull Terriers, several toy spaniels, Siberian Huskies, and Standard Schnauzers and others).  No mode of inheritance has been identified in breeds thus far studied.  The extremely low incidence in Aussies may indicate it is not inherited in this breed.

What does PHPV/PTVL mean for my breeding program?

To be safe, consider it a major fault,  Breeding an affected dog, especially if it has associated vision loss, is probably ill advised.  If the dog or its close kin are bred, avoid mates who have PHPV/PTVL or have a family history of it.  Also avoid dogs that had persistent hyaloids, since PHPV/PTVL is associated with the hyaloid artery.

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.  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.

What is micropapilla?

A smaller than normal optic disc – the point where the optic nerve enters the back of the eye.

How do I know my dog has micropapilla?

It would be discovered during an eye exam by a veterinary ophthalmologist.

What does having micropapilla mean for my dog?

Micropapilla does not cause any vision loss or pain.

How common is micropapilla in Aussies?

It is very rare.

Is micropapilla inherited I Aussies?

It is unknown whether it is inherited.

What does micropapilla mean for my breeding program?

Given the rarity of the condition and the lack of any good information on inheritance, treat it as a fault.  Don’t breed affected dogs to each other or to dogs with affected near kin.

What kind of eye defects do double merles have? 

Dogs that inherit two copies of the merle gene (“double merles”), usually have multiple eye defects, generally with associated vision loss which often goes to the point of blindness.  Any part of the eye can be affected.  Irises are frequently deformed, sometimes grossly so.  Pupils may be subluxated (off-center).  The lens may be subluxated (out of place).  The retina may be abnormal, and the optic nerve may be improperly developed.   The entire globe of the eye may be abnormally small (microphthalmia). Most double merles will have one or combination of these defects in each eye.  All of this can be avoided by not breeding merle dogs to each other.

What are Y suture lines? 

All dogs have Y sutures on the front and back of the lens.  They are the places where the lens tissue came together during prenatal formation. In some dogs, usually puppies, the lens sutures are especially prominent and can result in a note on an eye exam report.  Occasionally they remain prominent into adulthood, but so long as there is no associated cataract there is nothing to worry about.

What is corneal dystrophy?

Any of several diseases that cause degeneration of the cornea, the clear covering over the front of the eye.  Most are inherited but one type, which some argue should be called corneal degeneration, is not.  These diseases cause opacities of the cornea which may advance.  Inherited forms are bilateral (both eyes.)

How do I know if my dog has corneal dystrophy?

If you notice an opacity (cloudy spot) in your dog’s cornea, have it seen by a veterinary ophthalmologist.  Most corneal dystrophy cases are identified during eye exams.

What does having corneal dystrophy mean for my dog?

The disease is usually non-painful, but signs vary from breed to breed.  Some can advance to blindness, some will develop corneal ulcers which are painful and require treatment.  The disease cannot be cured.  Fortunately, cases noted in Aussies have usually been minor.

How common is corneal dystrophy in Aussies?

Very rare.

Is corneal dystrophy inherited in Aussies?

Corneal dystrophy can be an inherited in some breeds, but hasn’t been identified as such in Aussies.

What does corneal dystrophy mean for my breeding program?

If the dog has disease severe enough to require treatment, don’t breed it just to be safe.  Dogs with minor disease might be bred but not to other dogs with corneal dystrophy or those with near kin that are affected, again to be safe.  This may not be an inherited issue in Aussies.

Are puppy rye exams necessary?

Aussies are one of the breeds that should be routinely checked as young puppies.  Aussies can have Collie Eye Anomaly (CEA,) iris coloboma and persistent pupilary membrane (PPM), all of which are present from birth and can be identified in the puppy exam.  Occasionally a puppy will have distichiasis.  All Aussie puppies, even those who are going into non-breeding homes, need to be checked young.  If you wait, the development of pigment in the back of the eye can make detection of CEA impossible.