Eye Problems in Collies


For many years the British Veterinary Association (BVA), Kennel Club and the International Sheepdog Society (ISDS), have managed an eye scheme whereby a small panel of specialist veterinary ophthalmologists examine the canine eye for numerous breed-related, inherited problems. The results are then published quarterly in the Kennel Club's Breed Record Supplement. The BVA have some useful information on their website about eye diseases, where to find a certified eye panellist and current charges for testing. Click here to go to the BVA website.

Progressive Retinal Atrophy (PRA)

From the large number of eye problems affecting many breeds, Rough and Smooth Collies fortunately only have Progressive Retinal Atrophy (PRA) and Collie Eye Anomaly (CEA) to contend with. The BVA/KC/ISDS operates an official eye testing scheme, and it is recommended that puppies are clinically examined for CEA at 6-7 weeks, with the RPED (CPRA) test done at twelve months and annually thereafter.

PRA causes visual impairment and/or 'night blindness' due to the degeneration of the photo-receptor cells (rods and cones) of the retina. Although many different types of PRA affect numerous breeds, Rough and Smooth Collie breeders in the UK need generally only concern themselves with one type:

RPED or Retinal Pigment Epithelial Dystrophy (commonly referred to as CPRA)

RPED, or Centralised PRA, tends to affect British-bred Rough and Smooth Collies. Interestingly, neither Professor Peter Bedford nor the late Dr Keith Barnett have diagnosed any cases of RPED in Rough and Smooth Collies in recent years, albeit the numbers submitted for regular screening have been relatively low.

Although the actual mode of inheritance of RPED is not yet fully understood, it appears to be a non-congenital, multi-factorial, inherited disease. Several gene mutations may be involved, one of which causes the impaired metabolism of 'Tocopherol', an antioxidant found in vitamin E. Improved canine nutrition may well have led to a reduction in cases in recent years, as the incidence of RPED in those dogs tested under the KC/BVA scheme, appears to be less than 0.25%

Opthalmological signs of RPED may be detected in dogs of just over twelve months of age, but it is more usual to make an accurate diagnosis from eighteen months upwards as visual impairment of an affected dog tends to occur in later years. Peripheral vision may be retained for longer and not all dogs go blind. Vision is better in low light conditions, the dog's eyes having dilated pupils and showing poor light reflexes.

The slow nature of onset is the reason why breeders are encouraged to have their Collies clinically examined annually, when symptoms of both RPED and GPRA are routinely checked for. The KC's Accredited Breeder Scheme requires the eyes to be regularly checked, and certainly within eighteen months of registering a litter.
Canine Ophthalmologists agree that some breeds, like Rough and Smooth Collies, have a definite genetic predisposition towards RPED, but unfortunately(or fortunately for us!)  there are insufficient confirmed cases to warrant further research at this stage.

Consequently, no genetic test for RPED is likely to be available in the near future.

Generalised PRA or Rod/Cone Dysplasia type II (rcd2)

GPRA (rcd2) more commonly affects American-bred Rough and Smooth Collies. It is an early-onset, autosomal recessive inherited disease of bilateral nature, similar to the early-onset form of human Retinitis Pigmentosa ('night blindness').

Night blindness is the earliest clinical sign, detectable in six week old puppies, and by the time they are 6-8 months of age, rcd2-affected dogs may become blind. Abnormalities can be detected in the eye long before the owner is aware of visual impairment. Affected dogs eventually become totally blind, and cataract formation is common. There is no cure.

A genetic test for rcd2 was launched in the USA, in April 2008 - see www.optigen.com

Whilst GPRA is not usually found in British Collies, cases have been found in Europe and, with the recent imports of American dogs to Britain and Europe, our stock may be at risk in the future.'

Collie Eye Anomaly (CEA)

CEA has been well documented in numerous publications over the years. It is a non-progressive congenital eye disease prevalent in Rough and Smooth Collies, Border Collies, Shetland Sheepdogs, Australian Shepherds and Lancashire Heelers. CEA is an abnormality of the choroid layer of the eye, so is technically referred to as Choroidal Hypoplasia (CH). It presents itself as a pale patch (due to a localised lack of retinal and choroidal pigment) in the dorso-lateral region of the choroid, near the optic disc.

Very occasionally a coloboma, or hole, is present in the retina. This was originally thought to be CEA in its worst form. More recently, however, veterinary ophthalmologists believe it may be a different disease.

Since CEA was first made public in the 1960's the only way of detecting the disease has been by ophthalmic examination, with dogs being diagnosed as either 'clear' or 'affected' (mild to severe). Abnormalities of the choroid can be diagnosed in puppies as young as six to seven weeks of age.

The majority of Collies with CEA suffer no ill-effects and appear to show no visual defects, neither does the disease progress. In rare cases of CEA the Collie may suffer retinal detachment and in very mild cases clinically 'affected' puppies may 'go normal' before they reach one year of age.

It is most important to use the KC/BVA eye scheme to determine whether baby puppies are CEA 'clear' or affected and until recently we have had no way of knowing whether these 'clears' were genetically clear , 'carriers', or early 'go-normals'. Many breeders prefer to wait until their dogs are twelve months of age before first screening for CEA, in the hope that they will receive a 'clear' certificate. This twelve-month diagnosis may be misleading as a 'clear' dog will most likely be a 'go normal', and it is important to note that 'go-normals' are CEA-affected and can pass the defective gene onto their offspring.

A 'normal' or genetically clear-eyed dog (homozygous normal) receives two copies of the normal CEA/CH gene, one from each parent. Breeding two homozygous normal dogs together will therefore produce all normal-eyed or genetically clear offspring.

A CEA 'carrier' (heterozygous normal) receives a normal copy of the CEA/CH gene from one parent and a mutant copy from the other parent. The normal copy of the gene is the dominant one and it masks the recessive mutant gene, so such an animal will be diagnosed clear when clinically examined by opthalmoscope, though of course it is still affected.

When a carrier is mated it randomly passes on copies of both the normal and mutant genes to its offspring, so some will be affected and some normal-eyed. Breeding a carrier to a carrier will initially produce 25% normals, 50% carriers and 25% affecteds.

A CEA 'affected' dog (homozygous recessive) receives one copy of the defective recessive CEA/CH gene from each of its parents, so breeding two homozygous recessives together will produce only homozygous recessive or affected puppies.

'OptiGen' Genetic tests. DNA samples are used to test for both GPRA(rcd2) and CEA, so please check their web site for details - www.optigen.com or contact the organisers of the 20/20 clinics (details in the Dog Press).

The test involves blood, cheek swabs or semen samples being sent to the USA for screening, to determine the animal's genetic CEA status ie whether clear, carrier or affected.

Please note that, with CEA testing, the OptiGen test only determines the CH aspect of the disease and does not identify those dogs with detached retinas or colobomas. Breeders should therefore continue to have their 6-7 week old puppies clinically examined for CEA and associated problems, with any 'clears' being subsequently OptiGen tested.

Some clinically examined 6 week CEA 'clears', when OptiGen tested, are actually being diagnosed as genetically affected which, according to Professor Peter Bedford, proves the theory that these are cases of early 'go-normals'.'