Genetic Welfare Problems of Companion Animals

An information resource for prospective pet owners

Chow Chow

Chow Chow

Entropion

Related terms: In-turning of the eyelids, conformational entropion, developmental entropion.

Outline: Entropion is a deformity of the eyelids, common in Chow Chows, such that they are turned inwards resulting in the eyelashes constantly rubbing on the surface of the eye causing irritation, discomfort and pain.


Summary of Information

(for more information click on the links below)

1.  Brief description

In-turned eyelids cause the eyelashes and eyelid skin to rub on the surface of the eye. This can lead to irritation, pain and potentially permanent damage to the eyes.

2.  Intensity of welfare impact    

Constant irritation, discomfort and pain are common. Blindness due to keeping  the affected eye shut or due to scarring of the surface of the eye is also seen.

3.  Duration of welfare impact

Distress and pain are constant and potentially life long.

4.  Number of animals affected

Common in Chow Chows.

5.  Diagnosis

A diagnosis is made by a veterinary surgeon examining the eyes.

6.  Genetics

A breed predisposition is known in Chow Chow but the exact genetic causes are currently not known.

7.  How do you know if an animal is a carrier or likely to become affected?

Physical examination is the only way of determining the presence of entropion. Puppies should be examined carefully prior to purchase. It is recommended not to purchase a puppy if a parent has or had the condition.

8. Methods and prospects for elimination of the problem

The breed standard states that all animals should be free from entropion http://www.thekennelclub.org.uk/item/157). A programme involving not breeding from any animals that have had entropion may be effective in reducing the prevalence of entropion in the breed, but this is untested.

 

For further details about this condition, please click on the following:
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1. Clinical and pathological effects

Entropion is a condition in which the eyelid or part of an eyelid (and with it the eyelashes) turns in. Generally, the lower eyelids are more often affected but in the Chow Chow upper eyelids are also often involved (Helper 1989). Entropion results in irritation of the globe of the eye through repeated contact with facial hairs and eyelashes. This leads to increased tear production, conjunctivitis (inflammation of the conjunctiva -the tissues lining the eyelids), keratitis (inflammation of the cornea -the clear front surface of the eye) and abrasion and ulceration of the cornea. Increased tear production may lead to constant wetting of skin around the eyes which, in turn leads to irritation and secondary infection of the skin. A painful eye tends to be tightly held shut (blepharospasm). In itself this blepharospasm causes muscle pain and may cause the eyelid to impact further on to the eye (called spastic entropion). A painful eye suffers further from photophobia - the sensation that pain is worse when stronger light is falling upon it. Conjunctivitis often is associated with a discharge. Secondary infection will lead this to be pusy. Infection in the cornea can also occur leading to further damage here. Longer term corneal damage will lead to blood vessels growing into it as part of an attempted repair mechanism and the cornea becoming opaque and white in colour due to scar tissue)(Renwick 1996, van de Woerdt 2004). This, and the holding shut of the eyelids both cause blindness. Blindness due to corneal opacities may be permanent, even if the entropion is subsequently corrected using surgery (Moore 1993).

In  most breeds entropion is caused by having loose eyelids; however in Chow Chows it is usually caused by a narrow ocular opening (termed blepharophimosis or micropalpebral fissure) (Bedford 1980); described as an “oval” eye in the Chow Chow breed standard (http://www.thekennelclub.org.uk/item/157) . It should be pointed out that the breed standard also states that entropion should never be present.

Entropion can also be complicated by the presence of ectropion in some parts of the lids. Ectropion is where the eyelids are rolled outwards so that conjunctiva is exposed to the air. So called “diamond eye” is characterised by the presence of upper lid entropion and lower lid ectropion and is seen in some Chow Chows (Bedford 1980). 

Excessive loose skin on the face is seen in some Chow Chows. Both brow ptosis – the presence of excessive folds on the head above the eyes, and facial folds – excessive skin on the cheeks, can contribute to entropion (Barnet 1988, van de Woerdt 2004). All of these complications can mean that entropion in Chow Chows is more difficult to surgically correct than in other dogs, more extensive and multiple surgeries may be needed, with consequentially a greater impact of the dog’s well being.

Treatment of these defects involves surgery under anaesthesia, and attempts to create an ocular opening of a normal size by cutting the skin at either the medial or lateral canthus (where the upper and lower eyelids meet at each side of the eye), and lining this incision with conjunctiva. Techniques are also used to remove excessive skin from eyelids and folds around the eyes. Multiple operations are usually needed for Chow Chows with complicated abnormalities such as diamond eye (van de Woerdt 2004). 

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2. Intensity of welfare impact

The welfare impact of entropion varies from mild to severe. Most affected Chow Chows are expected to be suffering from constant irritation and pain which may be severe.

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3. Duration of welfare impact

Most dogs with the condition will suffer life-long pain without treatment. Treatment is not always successful and, in itself, can have significant welfare implications as it is based on surgery, and sometimes repeated surgeries.

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4. Number of animals affected

A significant breed predisposition to entropion has been reported for Chow Chows in the UK and USA (Hodgman 1963, Dorn 2002) and this is emphasised in many standard ophthalmology texts (eg Bedford 1980, Barnet 1988, Helper 1989, Maggs et al 2007).

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5. Diagnosis

Careful examination of the eye will lead a veterinary surgeon to make the diagnosis. Distinguishing to what extent entropion is due to structural abnormalities (a narrow ocular opening or loose eyelids) and how much is due to muscular contraction of a painful eye can be more difficult and involves applying local anaesthetic to the eye. Spastic entropion should resolve with local anaesthetic application – this is a diagnostic test rather than a treatment. More specialist examinations, requiring   staining of the tears and specialist equipment, will help to determine the extent of damage that has occurred to the eye itself. With moderate-severe disease the amount of pain in the eye can make it impossible to examine the eye properly without anaesthetising the dog. 

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6. Genetics

Chow chows are predisposed to entropion i.e. more likely to have this condition than other dogs. Entropion does not have a simple genetic cause and the exact genetic factors have not been established.

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7. How do you know if an animal is a carrier or likely to become affected?

A prospective owner should look for any inclination for the puppy to not hold its eyes completely open or to be blinking. There should be no discharges from the eyes.  Although some puppies may grow out of mild entropion, whether this will happen in a particular individual cannot be predicted. A veterinary examination can be sought.  Buying affected animals is likely to result in this welfare problem being perpetuated.

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8. Methods and prospects for elimination of the problem

The breed standard states that all animals should be free from entropion http://www.thekennelclub.org.uk/item/157). It seems very likely that avoiding breeding from any animals that have had entropion will be effective in reducing the prevalence of this welfare problem  but this is, as yet, untested.

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9. Acknowledgements

UFAW is grateful to Rosie Godfrey BVetMed MRCVS and David Godfrey BVetMed FRCVS for their work in compiling this section.

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10. References

Barnett KC (1988) Inherited eye disease in the dog and cat. Journal of Small Animal Practice 29: 462-475

Dorn CR (2002) Canine breed-specific risks of frequently diagnosed diseases at veterinary teaching hospitals. American Kennel Club. http://www.akcchf.org/pdfs/whitepapers/risk.pdf

Helper LC (1989) Diseases and surgery of the lids and lacrimal apparatus. In: Magrane’s Canine Ophthalmology 4th ed. Lea & Febiger, Philadelphia pp 51

Hodgman SFJ (1963) Abnormalities and Defects in Pedigree Dogs-I. An Investigation into the Existence of Abnormalities in Pedigree Dogs in the British Isles. Journal of Small Animal Practice 4: 447-56

Maggs DJ, Miller PE and Ofri R (2007) Breed predispositions. In, Slaters Fundamentals of Veterinary Ophthalmology, 4th edn. Saunders, Philadelphia. p 445

Moore CP (1993) Diseases of the eyelid, conjunctiva, and third eyelid. In: Disease Mechanisms in Small Animal Surgery 2nd edn. Ed. MJ Bojrab. Lea & Febger, Philadelphia pp 139

Renwick P (1996) Diagnosis and treatment of corneal disorders in dogs. In Practice July/August 315-18

van der Woerdt A (2004) Adnexal surgery in dogs and cats. Veterinary Ophthalmology 7: 284–290

© UFAW 2011


Credit for main photo above:

By Remigiusz Józefowicz (Own work) [CC-BY-SA-2.5-pl (http://creativecommons.org/licenses/by-sa/2.5/pl/deed.en)], via Wikimedia Commons