Genetic Welfare Problems of Companion Animals

An information resource for prospective pet owners

Standard PoodlePoodle (all types)

Hereditary Cataract

Related terms: Primary Cataract

VeNom term: Cataract (VeNom code: 521).

Related conditions: Diabetes mellitus; Lens-induced uveitis; Lens luxation; Glaucoma

Outline: A cataract is a disorder that affects the lens of the eye in which the lens becomes progressively cloudier. Cataracts cause blurred vision and eventually, when the entire lens becomes cloudy, they can cause blindness. Cataracts are not usually directly painful but the loss of vision and eventual blindness can cause confusion and possibly anxiety in dogs and may make them more prone to injury. Cataracts can be associated with other conditions, such as persistent inflammation of the eye or increased fluid pressure within the eyeball, both of which are painful and can cause permanent damage and irreversible vision loss. Large cataracts or those with complications can be removed via surgery to improve the quality of life for the dog.

Cataracts are a genetically complex condition and there is some evidence of a genetic basis for the development of cataracts. Although there are many causes of cataracts in dogs including aging, nutritional deficiency or primary eye disease, some cataracts are inherited in certain breeds and can develop when the dogs are young or middle-aged. Hereditary cataracts are relatively common in dogs, and have been reported to affect over 60 breeds, including the poodle (all types), which has an increased risk of developing cataracts compared with the general dog population.


Summary of Information

(for more information click on the links below)

1. Brief description

A cataract is disease of the eye, in which the lens of the dog’s eye becomes opaque and loses transparency; appearing cloudy or bluish-grey. Cataracts develop due to disturbances in the protein structure of the lens, where proteins and protein fibres clump together and prevent light from passing clearly through the lens. This causes blurred vision and loss of vision in dogs, and may lead to blindness if the entire lens becomes cloudy.

A cataract is not a painful condition in itself, but there may be associated conditions which are painful, including lens-induced uveitis which is common in dogs with cataracts. Uveitis is a condition where the middle layer of the eye, called the uvea, becomes inflamed causing loss of vision and pain ranging from mild aching to intense discomfort. Dogs with cataracts may also develop glaucoma (an increase in the fluid pressure of the eyeball) secondary to lens-induced uveitis or may develop lens luxation (in which the lens is displaced from its normal position). In both cases, these associated conditions can be painful and cause permanent blindness.

2. Intensity of welfare impact

Cataracts are the leading cause of blindness in dogs. There are several stages of cataracts – incipient (in which there is mild blurring to the lens), immature (in which vision is obstructed), mature (the entire lens is cloudy/opaque) and hypermature (in which the lens is shrunken in size). Early diagnosis and treatment of this disease is recommended.

Cataracts themselves are not thought to be painful, and the symptoms generally relate to the degree of vision loss, which in itself can cause confusion and may make affected dogs more prone to injury. Secondary complications of cataracts can lead to painful conditions, such as lens-induced uveitis, secondary glaucoma and lens luxation. Cataracts can be treated via surgery, which is invasive but tends to be effective. In some cases, scar tissue may develop on the lens and/or cataracts may return after surgery.

3. Duration of welfare impact

Dogs are born with normal lenses, which then start to degenerate over time leading to visual impairment and blindness later in life. Cataracts may remain the same in size and shape over time, but they may also progress leading to further vision loss and eventually blindness. Hereditary cataracts can be seen as early as 8 weeks in life, with vision becoming affected at 1 to 3 years. Owners may not recognise the problem or seek veterinary advice early on until the symptoms progress.

4. Number of animals affected

Overall in the UK, 20.3 dogs per 1000 animals (2%) were diagnosed with cataracts between 2009 and 2013 (VetCompass Infographic: http://www.rvc.ac.uk/vetcompass/learn-zone/infographics/canine). In American dog populations, all Poodle types had greater frequency of cataracts than other breeds or mixed breeds (Adkins and Hendrix 2005; Gelatt and Mackay 2005; Park et al 2009). Further, female Miniature/Toy poodles may have a higher risk of cataract development than males.

Poodles, and in particular Miniature and Toy poodle types, are more prone to develop diabetes mellitus, and this might explain why they are at an increased risk of developing cataracts, since the two conditions are linked (see [hyperlink]). One study has suggested that poodles with black or silver coats showed a higher susceptibility to cataract development, compared to white or apricot coats (Trbolová and Ledecký 2000).

5. Diagnosis

Cataracts are easily identifiable by a cloudy or blueish-grey mass in the dog’s eye, and an examination of the eye by a veterinary surgeon will confirm the presence of a cataract. In older dogs, cataracts must be distinguished from nuclear sclerosis, which is the natural change of the lens density in ageing animals and which does not affect vision.

6. Genetics

The mode of inheritance for cataract development in Miniature poodles is currently unknown, although an autosomal recessive inheritance is likely as with other breeds (Mellersh 2014).

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

Currently, there are no gene-based tests available for cataract development in poodles.

8. Methods and prospects for elimination of the problem

In the absence of complete information on hereditary cataracts, it is not advisable to breed from dogs affected early on in life, and from dogs of predisposed breeds with affected relatives, including grandparents, siblings, previous offspring and siblings of parents.


For further details about this condition, please click on the following:
(these link to items down this page)


1. Clinical and pathological effects

A cataract is disease of the eye, in which the lens of the dog’s eye becomes opaque and loses transparency; appearing cloudy or bluish-grey. They cause blurred vision and eventually, when the entire lens becomes cloudy, they can cause blindness in affected individuals. There are many causes of cataracts in dogs including old age, nutritional deficiencies (eg lack of antioxidants) or diseases of the eye. Some cataracts are inherited in certain breeds and can develop in young dogs, with diagnosis as early as 8–12 weeks of age. Cataracts in poodles occur in both eyes and are progressive. Dogs are born with normal lenses, which then start to degenerate over time leading to visual impairment and blindness later in life.

In cataract formation, the normal transparency of the lens is disrupted by the destabilisation of proteins, called crystallins. These crystallins abnormally clump together and bind to other proteins in the lens and this causes cloudiness and prevents lights from passing clearly through the lens, resulting in loss of vision. Since new cells form on the outside of the lens, older cells are compacted into the centre of the lens resulting in the cataract. Heat stress, oxidation or exposure to heavy metals can also cause this reaction. Genetic mutations in the crystalline protein structure can cause structures known as amoyloid fibrils to clump together, causing misting of the lens. Hereditary cataracts are common in dogs, and have been reported to affect 60 breeds, but are more common in specific breeds, such as poodles. Another common cause of cataracts is the diseases diabetes mellitus (Beam et al 1999), as it leads to excess sugars and water in the lens that cause loss of transparency of the lens.

There are important secondary complications of cataracts, including lens-induced uveitis which is common for dogs with cataracts. In this condition, the middle layer of the eye, called the uvea, becomes inflamed causing loss of vision and pain ranging from mild aching to intense discomfort. Uveitis can be difficult to treat effectively and the long-standing inflammation may result in traumatic rupture of the lens capsule. Over time, dogs with cataracts may develop glaucoma secondary to lens-induced uveitis or may develop lens luxation. Glaucoma is caused by an increase in fluid pressure in the eyeball, due to the fluid not draining away properly. Glaucoma can damage the nerve fibres of the eye. In lens luxation, the lens shifts out of its normal position in the eyeball, being displaced either to the front or back of the eyeball. In both cases, the condition can be painful and cause permanent blindness.

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2. Intensity of welfare impact

Cataracts are the leading cause of blindness in dogs. There are several stages of cataracts – incipient (in which there is mild blurring to the lens), immature (in which vision is obstructed) and mature (the entire lens is cloudy/opaque). Some mature cataracts progress to hypermature cataracts where because of loss of water and proteins the lens becomes shrunken in size. Early diagnosis and treatment of this disease is recommended.

Cataracts themselves are not thought to be painful, and the symptoms generally relate to the degree of vision loss, that in itself can cause confusion and anxiety in dogs and make them more prone to injury. People with cataracts report issues with light sensitivity, double vision and seeing colours. Secondary complications of cataracts can lead to painful conditions, such as lens-induced uveitis and secondary glaucoma. These conditions may irreparably damage the eye resulting in permanent vision loss. Cataracts themselves can be treated via surgery which is invasive but effective in most cases. In some cases, scar tissue may develop on the lens after surgery and/or cataracts may return after surgery. If the mutation exists in both eye lens, cataracts may also occur in the other eye at the same time or at different times. It is important to note that blind dogs may be able to adequately adjust to their vision loss, and this should be assessed for each individual dog. Before surgery careful consideration needs to be given, weighing the possible benefits of the intervention - ie the chances of success of the surgery and the improvement it will bring to the life of the animal against the possible costs – the pain, discomfort and risk associated with the surgery and possible complications thereafter.

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3. Duration of welfare impact

Cataracts may remain the same in size and shape over time, but they may also progress leading to further vision loss and eventually blindness. For Miniature poodles, the mean age at which cataracts were diagnosed was 9.6 years, ranging from 6.1 to 13.1 years (Park et al 2009), and this was significantly later in life than for other small breeds. However, hereditary cataracts can be seen as early as 8 weeks in life, with vision becoming affected at 1 to 3 years (Barnett 1985). Owners may not recognise the problem or seek veterinary advice early on until the symptoms progress.

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4. Number of animals affected

In the UK, 20.3 dogs per 1000 animals (2%) were diagnosed with cataracts between 2009 and 2013 (Vet Compass Infographic: http://www.rvc.ac.uk/vetcompass/learn-zone/infographics/canine) and in North America, 24.2 dogs per 1000 (2.4%) were diagnosed with cataracts between 1994 and 2003 (Gelatt and Mackay 2005).

In a study of 244 dogs with cataracts in University of Tennessee during 2001-02, 54 breeds were affected but miniature poodles had a significantly higher odds ratio for developing cataracts compared with mixed breed dogs (Adkins and Hendrix 2005). In one study in North America, 10.8% of Miniature poodles, 10.2% of Toy poodles, and 7% of Standard poodles (Gelatt and Mackay 2005), suggesting that they are more prone to cataract development than other breeds or mixed breeds. In a study of small breeds, Miniature/Toy poodles were shown to have the highest risk of cataract development, with 112 dogs out of a total of 561 small breed dogs with cataracts (20% of total dogs; odds ratio: 2.6, 95% confidence interval: 2.1-3.2), and in this particular study, female Miniature/Toy poodles were twice as likely to have cataracts than males (95% confidence interval: 1.3-3.2; (Park et al 2009)

Studies across USA and Europe have suggested that Poodles, and in particular Miniature and Toy types, are consistently overrepresented in diabetic dog populations versus non-diabetic populations (Fall et al 2007), and this might explain why they are at increased risk of developing cataracts, since the two conditions are linked. One study has suggested that Poodles with black or silver coats showed a higher susceptibility to cataract development, compared to white or apricot coats (Trbolová and Ledecký 2000).

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5. Diagnosis

Cataracts are easily identifiable by a cloudy or blueish-grey mass in the dog’s eye, and an eye examination by the veterinary surgeon (or specialist veterinary ophthalmologist) can confirm the presence of a cataract. Dogs may be referred to a specialist veterinary ophthalmologist for monitoring and treatment. In older dogs, cataracts must be distinguished from nuclear sclerosis, which is the natural change of the lens density in ageing animals and which does not affect vision. Cataracts are usually classified by their age of onset (congenital, juvenile, senile), anatomic location, cause, degree of opacification (incipient, immature, mature, hypermature), and shape.

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6. Genetics

Cataract development in dogs is a complex inherited disorder, involving multiple genes. The mode of inheritance for cataract development in Miniature poodles is currently unknown, although an autosomal recessive inheritance is likely as with other breeds (Mellersh 2014).

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

Currently, there are no gene-based tests available for cataract development in poodles.

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8. Methods and prospects for elimination of the problem

The genetic basis of cataract formation is complex and unknown for the poodle breeds, therefore elimination of the problem is therefore difficult. Further genetic studies are required to identify the genes involved in cataract development, and to develop screening tools to help reduce the problem. In the absence of specific information on the nature of inheritance of cataracts in this breed, it is advisable to avoid breeding between moderately or severely affected individuals (ie those with rapid and progressive cataract development) or from dogs with severely affected relatives, including grandparents, siblings, previous offspring and siblings of parents.

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9. Acknowledgements

UFAW thanks Dr Emma Buckland (BSc, PhD), Dr David Brodbelt (MA VetMB PhD DVA DipECVAA MRCVS) and Dr Dan O’Neill (MVB BSc, MSc, PhD, MRCVS) for their work in compiling this section.

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10. References

Adkins EA and Hendrix DVH (2005) Outcomes of Dogs Presented for Cataract Evaluation: A Retrospective Study. Journal of the American Animal Hospital Association 41: 235–240. doi:10.5326/0410235

Barnett KC (1985) The diagnosis and differential diagnosis of cataract in the dog. Journal of Small Animal Practice 26: 305–316. doi:10.1111/j.1748-5827.1985.tb02204.x

Beam S, Correa MT and Davidson MG (1999) A retrospective-cohort study on the development of cataracts in dogs with diabetes mellitus: 200 cases. Veterinary Ophthalmology 2: 169–172

Fall T, Hamlin HH, Hedhammar A, Kämpe O and Egenvall A (2007) Diabetes mellitus in a population of 180,000 insured dogs: incidence, survival, and breed distribution. Journal of Veterinary Internal Medicine / American College of Veterinary Internal Medicine 21: 1209–1216. doi:10.1111/j.1939-1676.2007.tb01940.x

Gelatt KN and Mackay EO (2005) Prevalence of primary breed-related cataracts in the dog in North America. Veterinary Ophthalmology 8: 101–11. doi:10.1111/j.1463-5224.2005.00352.x

Mellersh CS (2014) The genetics of eye disorders in the dog. Canine Genetics and Epidemiology 1: 3. doi:10.1186/2052-6687-1-3

Park SA, Yi NY, Jeong MB, Kim WT, Kim SE, Chae JM and Seo KM (2009) Clinical manifestations of cataracts in small breed dogs. Veterinary Ophthalmology 12: 205–210. doi:10.1111/j.1463-5224.2009.00697.x

Trbolová A and Ledecký V (2000) The relationship between the occurrence of lens cataract and progressive retinal atrophy and some categories of poodle breeds. Folia Veterinaria 44: 12–16

© UFAW 2015


Credit for main photo above:

By B. Schoener (Flying Spark at de.wikipedia) (Own work) [Public domain], via Wikimedia Commons