Category: eye disease

PRA (also known as generalised progressive retinal atrophy or GPRA) describes a group of inherited eye diseases of dogs. PRA leads to slowly progressive blindness over a period of months or years.

PRA has been reported in more than 100 different dog breeds, but in the UK it is most commonly seen in poodles (miniature and toy), cocker spaniels and Labrador retrievers.

The earliest sign is usually poor vision at night or in dimly lit surroundings. Affected dogs may become more cautious or nervous about going outside after dusk. Over time, vision deteriorates further until day vision also becomes affected. Affected dogs may lose peripheral vision and develop tunnel vision.

The pupils may appear dilated and increased eye shine may be evident. In some dogs cataracts may develop secondary to the PRA so that the eyes appear cloudy.

The age at which signs of PRA develop varies between breeds. Typically, PRA affects middle-aged dogs (3-8 years old) although in some cases clinical signs may not develop until later in life. In a few breeds (such as the miniature schnauzer) signs may develop earlier.

Confirmation of PRA is made by examining the back of the eye with an ophthalmoscope to look for characteristic signs of retinal degeneration. If the retina cannot be examined (e.g. if secondary cataracts are present) then a test called an ERG (electroretinogram) may be performed. Your vet can refer you to a specialist veterinary ophthalmologist for this test.

DNA tests are also available for some breeds of dog. DNA tests are particularly useful in young dogs or those which may be used for breeding because they can identify affected dogs before they develop signs of PRA. They can also identify carrier animals. Carrier dogs will not develop PRA themselves but may pass the disease on to their offspring.

Unfortunately there is currently no effective treatment for PRA and affected animals will become totally blind, usually over a period of months to years. Because of the slow progression of the disease, however, most dogs learn to adapt to their blindness and continue to lead contented lives.

As PRA is an inherited disease, affected animals should not be used for breeding.

Keratoconjunctivitis sicca (KCS or ‘dry eye’) develops when insufficient tears are produced from the tear glands. Tears keep the surface of the eye moist, help to flush away surface debris (such as dust landing on the cornea), provide lubrication to aid blinking, and have antibacterial properties to fight infections. Reduced tear production may affect all of these important functions. Over a period of time, affected eyes may become blind due to scarring and pigmentation of the cornea.

The most common cause in dogs is when the body’s own immune system attacks the tear glands, which are then gradually destroyed over a period of months or years. What exactly triggers this attack to make some dogs develop KCS is unknown.

Usually both eyes are affected, although sometimes to different degrees. Clinical signs include the following:

• Conjunctivitis, which may respond to antibiotic treatment but has a tendency to recur.
• A sticky grey discharge from the eyes (this discharge may turn white, yellow or green if it becomes infected).
• Clouding or dullness of the cornea.
• Discomfort around the eyes – the animal may blink more than normal or rub at its eyes.

KCS is diagnosed by performing a Schirmer tear test. This simply involves placing a strip of filter paper against the cornea and measuring the degree of wetting over the course of 1 minute. The Schirmer tear test is quick and easy to perform, and well tolerated by the patient.

Your vet will be able to give you something to help your pet if they have dry eyes. The aims of treatment are to keep the eyes comfortable and to minimise the scarring and pigmentation caused by KCS, which may lead to blindness if left untreated. Most cases of KCS will need lifelong management. Treatments will vary from case to case.

Medication to stimulate tear production

In most cases, the first-line treatment is ciclosporin 0.2% eye ointment (Optimmune™). This treats the underlying cause of KCS by reducing the immune system attack on the tear glands. For optimal results there must be some residual tear gland function, so this treatment works best in mild to moderate cases. It is usually very effective, but treatment must be given twice daily every day, and lifelong treatment is usually required. If Optimmune™ fails to work, then in some cases other similar types of drug may prove effective (for example ciclosporin 1% solution or tacrolimus).

Lubricants/ artificial tears

Various types are available. These include drops, gels and ointments to keep the surface of the eye moist and prevent evaporation of tears. These do not treat the underlying cause, but instead help to replace the tears that are not being produced. They are often used in conjunction with Optimmune™.

Antibiotics

Corneal ulcers and bacterial infections occur quite commonly in dogs affected with KCS and so a course of antibiotic eye drops may be prescribed from time to time.

Surgery

Parotid duct transposition (PDT) can be performed if the above treatment proves ineffective. This surgery involves relocating a duct of one of the salivary glands from its usual opening into the mouth to inside the lower eyelid. Saliva is then secreted onto the surface of the eye and acts to keep the surface of the eye moist.

In many cases, this proves a very effective treatment. However, saliva is not exactly the same as tears, so in a few cases it may cause problems such as irritation to the surface of the eye or to the skin around the eye. For this reason, PDT is usually reserved as a last resort should medical management fail.

Whatever treatment is recommended, lifelong management will usually be needed and regular visits to your vet will be required in order to monitor tear production and ensure that the eye is responding successfully to treatment.

A corneal ulcer is a hole in the clear covering of the front of the eyeball (the cornea). Sometimes only the top layer of the cornea (the epithelium) is affected but in some cases the damage may go deeper and become more difficult to treat. On rare occasions a corneal ulcer can become infected with bacteria that may produce toxins. These toxins can destroy the surrounding normal tissue, leading to a rapid deepening of the ulcer that can cause loss of the eye unless treated quickly and appropriately.

Common causes include:

• External trauma (e.g. by a thorn or cat claw).
• A foreign body such as a piece of grit or grass seed caught under the eyelid.
• Eyelashes or hairs growing in the wrong place on the eyelid.
• Inherited/ breed-related problems such as in-turning of the eyelids (entropion).
• Some bacterial or viral infections can also cause corneal ulceration, or exacerbate an existing ulcer.
• If your dog is unable to produce tears (a condition known as ‘dry eye‘) the eye may also be more susceptible to corneal ulcers. In some cases the cause of the ulcer is uncertain.

Ulcers can be very painful and your dog may resent being touched around the affected eye. Your dog may blink frequently, keep the eye partially closed, or rub at the eye. There may be a watery discharge from the eye (if the corneal ulcer becomes infected this discharge may become purulent).

The white of the eye may become reddened and if the ulcer is particularly painful the third eyelid (a protective membrane under the main eyelids) may cover the surface of the eye when the eye is open (this can give the appearance of the eye ‘rolling up into its socket’).

Your vet will try to identify the cause of the ulcer in order to choose the best treatment. The eye must be examined carefully to make sure there is nothing rubbing against the eye. Your vet may check for ‘dry eye’ by using a small strip of filter paper placed inside the lower eyelid in order to check tear production. Local anaesthetic drops may be put in the eye to make your dog more comfortable whilst the eye is examined.

Your vet will then put a few drops of dye into the eye. This green dye sticks to the damaged areas and will show your vet how far the corneal ulcer extends.

The choice of treatment depends on the type of injury and how far it extends. If there is an underlying cause (such as a foreign body, eyelid abnormality, or dry eye) then it must be identified and treated.

For minor corneal ulcers your vet may prescribe antibiotic eyedrops or ointment. The aim of this is to prevent the ulcer becoming infected whilst it is healing. Uncomplicated corneal ulcers should heal within 5-7 days. If the ulcer takes longer than this to heal, there may be an underlying cause or complication that should be investigated.

More severe ulcers may require additional treatment and in some cases this may include surgery. Various surgical procedures are possible, depending on the type and severity of the ulcer. In difficult or protracted cases your vet may recommend referral to a specialist veterinary ophthalmologist.

During treatment, an Elizabethan collar may be necessary to prevent your dog rubbing the eye and causing further damage. As the eye heals, the area around the ulcer may become redder and small blood vessels start to grow across the eye surface to help the healing process.

When the ulcer has healed there may be a small indentation or scar left on the eye surface, but in the majority of cases this is unlikely to affect your dog’s eyesight.

Your vet is likely to ask you to put drops or ointment into your dog’s eye during the healing stage. This is relatively straightforward in most dogs with a bit of practice.

1. Hold your dog firmly and tilt its head upwards.
2. With the thumb and finger of the holding hand, the eyelids should be pulled gently apart and the medication given with the other hand.
3. The tip of the tube should be held parallel with eye surface, not pointed directly at it.
4. Expel a single drop onto the surface of the eye, taking care not to touch the surface of the eye with the tip of the dropper because this may damage the eye or spread bacteria from the eye back into the contents of the bottle.

Almost all corneal ulcers are treatable, as long as the cause and type of ulcer is identified and the correct treatment is given. Early treatment gives the best chance of a good recovery. If your dog’s eyes appear sore or red or if any abnormal discharges are present you should make an appointment to see your vet immediately.

The conjunctiva is the pinkish surface surrounding the eyeball. The third eyelid is an extra protective eyelid in the dog and is also covered by conjunctiva. In normal dogs the conjunctiva is not readily visible. In conjunctivitis this membrane is inflamed and becomes red and swollen. Conjunctivitis can affect one or both eyes.

Dogs with conjunctivitis usually have a discharge from their eye(s). This can be clear and watery or thick and greeny/yellow in colour. The conjunctiva is often more visible and may be swollen, partially covering the eye. The eye(s) may be held half closed and the third eyelid is more prominent.

A number of different conditions will cause conjunctivitis. Many are sudden in onset and easily treatable. Others cause a long term disease which can be more difficult to control.

1. Irritants, trauma (e.g. a cat scratch) and foreign bodies (e.g. grass seeds) can cause conjunctivitis. In most cases treatment is rapidly effective once the cause has been removed.
2. Conjunctivitis in dogs usually occurs as a consequence of some other eye problem. In dogs with sagging skin, the deformity of the eyelids can make them more prone to eye infections. In some dogs the eyelids turn inwards and hairs on the eyelid can rub against the eye causing damage and increasing the risk of infection.
3. A further problem in some dogs is abnormal tear production, inadequate lubrication of the eyes can result in damage to the eye surface.
4. Disease of the immune system can also cause conjunctivitis. These diseases are not common but can be difficult to treat.

Usually your vet will be able to tell that your dog has conjunctivitis by a simple examination. Your vet will want to examine the eye carefully to be sure there is no damage to the eye itself. If there is no obvious traumatic cause most cases will respond to drops or ointment containing antibiotics and anti-inflammatory drugs.

It is also important to be sure that tear production in the eye is normal. Your vet will be able to do a simple test in the consulting room to check this if necessary. If a foreign body is present then this obviously needs to be removed.

If the signs are not getting better after a few days of treatment, or appear to improve only to get worse again when treatment stops, more investigation is required. Your vet will want to take a swab from the conjunctiva to look for infection. In some cases a blood sample may also be required.

If there is no infection then it can be helpful to look at a sample of cells from the conjunctiva. This sample is obtained by gently scraping the surface of the conjunctiva with a cotton wool swab or spatula. If a larger sample is required, then a section of conjunctiva taken surgically may be necessary.

In most cases conjunctivitis is treated by application of drops or ointments to the eye. Sometimes with particularly stubborn infections antibiotic treatment may also need to be given by injection or tablet.

It is essential to treat any underlying causes of conjunctivitis at the same time – if these are not dealt with the problem will keep coming back. Treatment may be needed to control problems with the immune system and if the eye is too dry then replacement tears may be required. If the tear replacements are needed they are most likely to be required lifelong.

If you are able to treat your dog’s eyes this can be done at home but regular treatment is essential. Most drops or ointments need to be administered at least 3-6 times a day. If you have any doubts as to how to give the medication prescribed, please ask your veterinary practice to give a demonstration. If you are unable to treat your dog appropriately your vet may arrange to keep it in the hospital for a few days to ensure that effective treatment is given.

Light enters through the front of the eye and is focused by the clear lens onto the retina, which lies at the back of the eye. Information from the retina is transmitted to the brain where processing occurs.

For the lens to work correctly, it must be perfectly clear. In cataract, the lens becomes opaque (like frosted glass) or even completely white. Light does not pass through it well in this state and vision is reduced. Severe cataracts cause blindness.

There are several different causes in dogs:

• Cataract development can be inherited from parents in many different dog breeds. Hereditary cataracts affect both eyes – usually, but not necessarily, at the same time. Hereditary cataracts can be present at birth (congenital) or, more commonly, they may develop in young adult dogs.
• Cataracts are common in dogs suffering from sugar diabetes due to disturbances in the metabolism of the lens caused by abnormal blood glucose levels.
• Cataracts can arise following severe inflammation in the eye, or as a result of poisonings or nutritional imbalances.
• Cataracts can also be associated with glaucoma (increased pressure within the eyeball), disease of the retina (at the back of the eye) and when trauma has resulted in dislocation of the lens of the eye from its normal position.

Usually owners are alerted to the fact that their pet may have a problem with its eye when they notice a whiteness of the eye. If eye disease develops gradually, dogs are often able to adapt well and use their other senses to help them get around. Dogs have very good hearing and a sense of smell and can use these to compensate for poor vision to some extent. In familiar surroundings it may be almost impossible to tell that a pet cannot see. If you are worried about your pets vision you can test it yourself using some simple exercises:

1. Observe your dog carefully in the home environment and out of doors
   Does he appear to be having any visual difficulty?
2. Throw light, silent objects (e.g. a ball of cotton wool) in front of your dog’s eyes
   Does he see and follow these?
3. Construct a small obstacle course in the home, or move furniture around and away from the usual positions
   Does he see and avoid these obstacles the first time?

Repeat the above tests in daylight and in subdued lighting.

If you are concerned about the results of the report them to your veterinary surgeon and ask for a check-up for your pet.

In older dogs, the lens of the eye may take on a bluish or grayish color. Many owners believe this is a cataract. However, a simple eye examination usually provides the necessary reassurance. This problem is called nuclear sclerosis and is part of normal ageing. Vision is preserved and no specific treatment is needed.

Diagnosis is usually straightforward, and based upon visual testing of the dog and examination of the eye by a veterinary surgeon/ophthalmologist. Additional tests may be required to check for diabetes and occasionally other causes and other eye diseases.

Cataracts are treated by removing the lens from the eye. The lens is surgically removed by a specialist. There are several different techniques but one of the most popular is known as phacoemulsification (the use of ultrasound waves to break up the cataract). Once the lens has been broken up fragments can be removed through a small incision in the eye. Other surgical techniques are also possible and may be indicated in certain cases, e.g. when lens of the eye has become displaced.

Following surgery the aftercare is very important. Eye drops may be required for several months and must be applied regularly at home. If cataracts are present in both eyes, they may be removed at the same time, thus avoiding the need for further surgery in the future.

The scheme was introduced to try to reduce the numbers of pedigree dogs affected by inherited eye diseases. Although the scheme was developed to test for inherited eye disease in pedigree dogs any dog may be tested.

Many of the conditions covered by the eye scheme can lead to painful and/or blinding eye conditions. Generally, dogs with hereditary eye diseases should not be used for breeding.

The scheme is updated on January 1st each year so it is important to check regularly whether new breeds or conditions have been added.

The routine eye test can be performed on any dog over the age of 12 weeks. It is important that the eye test is carried out prior to breeding and, because many of the eye conditions do not develop until later in life, it is recommended that actively breeding dogs are tested annually.

An additional test called gonioscopy is performed in those breeds at risk of primary glaucoma (high pressure within the eye). Gonioscopy can be performed from 6 months of age. Traditionally, the test was only performed once in a dog’s lifetime. However, because the condition can be progressive in the Flatcoated Retriever, it is now recommended every 3 years in this breed. It is likely that the advice for other breeds will change in time as more information comes to light about this disease.

Litter screening of puppies is also available under the scheme. This is best performed when the puppies are between 5-8 weeks of age. The litter screening looks for evidence of congenital hereditary eye disease.

The Panellists appointed by the BVA are vets with postgraduate qualifications who specialise in eye examinations (ophthalmologists). They are accredited on a regular basis to ensure they have the necessary experience and skills to perform the examination. Since they examine so many dogs’ eyes on a regular basis they are very familiar with all the possible appearances of eyes (whether normal or abnormal) and thus are best placed to perform the Eye Test.

The BVA provides a list of contact details for vets (Panellists) who are qualified to do eye testing in the UK and Eire. This list can be found on the BVA and the Kennel Club websites. You can make an appointment to see a panellists yourself – you do not need a referral from your vet. Alternatively, many breed societies organise eye testing sessions at dog shows. The cost of testing is fixed by the BVA and price lists can be found on their website.

As from January 1st 2010 permanent identification (usually microchipping, although permanent tattooing is acceptable) has been required for all dogs, other than Border Collies registered with the International Sheep Dog Society (ISDS), before they can be examined and certified under the eye scheme.

If your dog does not have permanent identification then it cannot undergo eye testing under the eye scheme. It is worth checking that your dog’s microchip is readable on a regular basis because, if it cannot be read by the Panellist, the eye test cannot be completed.

You will need to show your original KC or ISDS owner registration documents so make sure you take these with you. The Panellist cannot issue an Eye Test Certificate without checking and stamping these.You should also take along any previous eye certificates issued to your dog.

For the routine examination, drops need to be applied to dilate the pupils so that the back of the eye can be examined. The drops can take up to 30 minutes to take effect and you will need to wait until the eye test can be performed. The Panellist will examine your dog’s eyes with a range of ophthalmic equipment that allows them to examine in detail the structures within the eye.

In some breeds of dog that are at risk of developing glaucoma (increased pressure in the eye) the vet will do an additional test before the routine examination and dilation of the pupil. This is called gonioscopy and involves placing a specialised lens onto the surface of the eye, following application of local anaesthetic eye drops.

The Panellist will tell you the results of the examination at the time of the test and you will receive a certificate of eye examination for each dog examined. The certificate consists of three sections. The first section records the details of the dog and owner, and requires an owner signature. The second section describes any eye abnormalities noted during the examination. The third section is a list of inherited eye diseases which will be ticked as either affected or unaffected for those known to affect the breed under examination. This section is only completed for dogs registered with the KC or ISDS and only for those with conditions currently certified under the Eye Scheme.

Your dog’s registration document will be stamped and signed by the Panellist. You will receive a copy of the certificate and additional copies will be sent to the Kennel Club, to your own vet and a copy kept by the ophthalmologist.

You are entitled to lodge an appeal against the results of an eye examination. This must be done in writing to the BVA within 30 days of the examination. You may then take your dog, along with the certificate in question, for examination by another Panellist (who will charge the normal fee for the eye test).

If the second Panellist agrees with the first, the appeal is deemed to have failed. In such a case, no further appeal is allowed. If the second Panellist disagrees with the first Panellist, the dog is referred to the Chief Panellist for further examination without an additional fee to the owner. The decision of the Chief Panellist is deemed final.

There are a growing number of inherited eye conditions for which DNA tests are available. An up to date list is included on the KC website (http://www.thekennelclub.org.uk/media/14688/dnatestsworldwide.pdf). Many of these tests can be performed on material collected on a swab from the dog’s mouth, although others require a blood sample to be taken.

These tests are very helpful in breeding schemes, especially in the case of recessively inherited diseases as they are able to identify carrier dogs (i.e. those which do not develop the disease in question but can pass the underlying gene mutation to their offspring).

However, although these DNA tests are very accurate for detecting abnormal genes they are very specific. Each DNA test can only look for one condition whereas the eye examination covers all possible eye diseases and is critical in the detection of emerging inherited eye diseases. Thus, DNA tests will never replace the need for the eye examination.

Further information

• Information on all the current tests is available from the BVA at www.bva.co.uk
• Further information on breed schemes is available from www.the-kennel-club.org.uk

At first glance that may seem like a strange question. However, dogs vary in their response to blindness. Dogs that go blind slowly usually cope better than dogs that become suddenly blind because they learn to adapt to their reducing vision. Older, slower dogs tend to cope better than younger, more boisterous ones.

Some dogs that have lost their sight over a long period of time navigate around so well that their owners do not recognise that they are blind. As dogs lose their sight they often initially become more cautious about going out in the dark and may be disorientated in dim lighting conditions.

Animals that are totally blind do not cope well in novel surroundings and may be unwilling to walk off the lead or may bump into objects.

In general, most dogs learn to cope very well with being blind, although inevitably there are exceptions. There are a number of things that you can do to help your dog adapt to blindness:

Keep their environment consistent

Blind dogs gradually develop a mental spatial map of their environment. This enables them to negotiate their way around familiar surroundings (this mental map can be accurate enough to convince many owners that their dog does retain some vision, even when totally blind).

• Owners can help their pet develop a mental map by initially restricting their access to a small area of the house and garden before gradually extending the area. This is particularly important in cases of sudden onset blindness, or if a blind pet moves to a new home.
• Try to keep items of furniture in familiar positions.
• Avoid leaving objects in unfamiliar places (e.g. shopping bags on the floor).
• Leave food and water bowls in the same place.
• Leave the TV or radio on when your dog is left alone. The sound acts as an auditory cue to allow them to orientate themselves within the house.
• Place tactile cues to aid orientation around the house. For example, placing mats at every room entrance allows blind dogs to feel these under their paws, thus helping them to orientate themselves within the house and negotiate their way into rooms. Likewise, in the garden they can learn to negotiate by locating paths or grass beneath their pads.
• Take care in unfamiliar environments. It obviously makes sense to keep blind dogs on a lead or harness on walks.
• Take particular care when meeting other dogs. Much of the initial social interaction between dogs is based on visual cues, for example determination of dominant or submissive status. Blind dogs are unable to respond to such visual cues, and as such are more at risk of attack should they encounter a dominant dog.

Consider training

It can be helpful to consult an experienced dog trainer or behaviourist who may be able to give advice on ways that training can help improve the confidence and ability of blind dogs. Such considerations may include:

• Positive reinforcement to increase their confidence.
• Increasing their repertoire of auditory commands.
• Use of training aids such as whistles.

Stimulate their other senses

Remember that a blind dog still retains four other senses. Set aside some time to stimulate these, for example by giving your dog a daily massage and by getting used to talking to your pet more than you might to a visual dog. Whilst it is tempting to want to spoil your dog by feeding regular treats, bear in mind that blind dogs are likely to exercise less than visual ones, so try to ensure that weight control is maintained.

• Caroline D Levin (2003) Living With Blind Dogs. Second Edition, Lantern Publications (ISBN 09672253).
• http://www.dummies.com/how-to/content/living-with-a-blind-dog.html
• http://www.blinddog.info/blinddoghelp.htm