If you are a dog owner, you will want to be aware of the most common eye problems in dogs. Of course, some breeds are more prone to eye problems than others, so make sure that you read up on your specific breed. The most common eye problems in dogs include cataracts, Glaucoma and Lens Luxation.
Cataracts in Dogs
The most common eye problems in dogs include cataracts and specifically a hereditary condition called juvenile cataracts. They are seen in all breeds but particularly Boxers. Cataracts can occur as early as 6 weeks of age, or they may not show up for a year, which makes it very difficult to breed from affected animals. Some of the symptoms include:
1. Inability to maintain visual fixation – the dog turns his/her head when looking at something, or they fail to follow objects with their eyes.
Another symptom is a strabismus (crossed eyes), which could be due to an eye tumor or other disease, but in most cases of cataracts then dog will not show the neurological signs of strabismus.
2. Decreased or absent accommodation – inability to change the focal length of the eye, difficulty focusing on near/far objects.
3. Abnormal pupils – size and shape variation in both eyes, commonly both pupils are different sizes but they may also be unequal in size and shaped differently.
The pupils may dilate or constrict inappropriately to light.
4. Dilated, full white-of-the-eye – the white of the eye is seen as a solid, dull white area with no colored portion of the eye.
5. Painful eyes – dogs will be observed scratching at their eyes and pawing at objects; they may squint and stare toward lights when in pain.
6. Nystagmus (eye twitching) – the dogs eyes twitch back and forth, sometimes so severely that it has to hold its head still or keep moving forward when walking.
7. Blind – sudden onset blindness for one eye can be a sign of tumour, but in most cases it is due to cataracts.
A congenital condition, juvenile cataracts are hereditary and caused by the presence of extra pigment cells within the lens. The pigment cells clump together to form a white deposit (known as a nuclear sclerotic) which causes opacity on the lens. These deposits have been reported to be present in almost every lens cell from a dog that has juvenile cataracts.
Because the age of onset is so young, breeders try and avoid breeding any affected animals. The condition is inherited as a recessive trait which means an animal has two copies of the gene (one from each parent), and therefore will be affected. Animals need to be examined at a young age so that breeders can identify any affected dogs and not breed from them. The parents of an affected animal may not show symptoms themselves but it is possible they are carriers. If both parents carry the faulty gene then there is a 25% chance with each litter that the offspring will inherit two copies and develop the disease.
Glaucoma in dogs
is one of the leading causes of blindness in dogs. It is caused by a buildup of pressure, which happens when fluid can’t escape out of the eye fast enough due to a narrow opening-known as a “canal” or circle drainage system-between the iris and cornea. This build up will cause elevated intraocular pressure (IOP) and thickening of the cornea that will lead to permanent loss of vision.
A dog is considered glaucoma suspect if they exhibit:
1. Pain, redness, or a discharge from their eyes; these symptoms can be caused by something like a scratch or bacterial infection but it can also indicate glaucoma.
2. Squinting, excessive blinking, or a change to the shape of the eye; these are all symptoms that can indicate glaucoma if there other additional signs.
3. A smaller pupil and/or an enlarged iris-this could be due to a congenital defect but is also common in glaucoma patients.
As with many conditions, the earlier you detect it, the better chance of a cure. Glaucoma is treatable but once permanent blind spots are formed they will not go away on their own and if left undetected for too long dogs may develop additional health problems such as cataracts or glaucomatous optic atrophy.
Glaucoma is a leading cause of blindness in dogs, but it also occurs in cats and horses. It is estimated that 1% of all canine glaucoma cases are hereditary. Conventional treatment for the disease includes blocking or “tacking” open the drainage system with medication, though this does not always work well due to side effects. Surgery can also be done to remove the drainage system but again, not always with good results.
Glaucoma in dogs is treatable with surgery or medication and early detection is key to increasing chances of a cure.
Lens Luxation
There are several types of lens luxation-this means the lens has slipped out of place within the eye. A dislocated lens can be either anterior (towards the front of the eye) or posterior (towards the back of eye). The dislocation can occur on one or both eyes; it may be obvious immediately, but in many cases it is not apparent for some time. Anterior lens luxation usually occurs in dogs aged 5 years or younger. Posterior lens luxations occur in older dogs, typically aged 8 years and above.
Anterior lens luxation can cause damage to the cornea as it rubs against the iris, leading to an ulcer that eats away at the eye-this is known as “scurvy”.
Lens luxation is hereditary, and affected animals should not be bred from. It is thought to occur in certain breeds, including the Yorkshire Terrier, West Highland White Terrier, and Cairn Terrier potentially due to an inherited abnormality in the zonule fibers which anchor the lens. This is only a hypothesis based on research findings; it is not yet confirmed.
It is recommended that dogs are screened for lens luxation before breeding. If one parent has the condition there is a 50% chance their offspring will inherit it, and if both parents are affected then this increases to 75%. The canine eye examination should include pupillary light reflex test (PLRT) and tonometry testing; these tests can be done by a vet.
Eye injury in dogs
Of course the best methods for controlling eye injuries in dogs are preventative. There are several things you can do to prevent eye injury in dogs:
1) Keep all harmful chemicals and other potentially dangerous items out of reach (i.e. toothpaste, makeup remover, etc.).
2) Use fly repellents on your dog’s face if you live in an area with lots of insects.
3) Choose topical flea/tick medications that are safe for the eyes; some can be harmful, including Frontline and Advantix which contain pyrethrins that can cause chemical burns to the eye.
4) Do not use fireworks-the flash can cause temporary blindness, light sensitivity and even skin burns. The fuse or firework itself being blown into the face can cause trauma to the eye.
5) Never use a broom handle to discipline your dog; this could damage their eye(s). Using hands, feet, water guns are other ways to train your dog without causing harm.
6) If you notice your dog is limping or seems to be unsteady it may have sustained an eye injury. Limping could occur if there is damage to the eyelid, cornea or tear ducts; it can also indicate a fracture of the bones surrounding the eye. If you suspect your dog has an eye injury, then you should take it to the vet immediately.
For more information on eye problems in dogs, contact your local veterinarian.
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