Conjunctivitis in Dogs

The eyes of the dog are highly sensitive, their vision is similar to that of a red-green colour blind human but with increased sensitivity in dim light and just like humans a dog’s eyesight is a precious and valuable sense. The complex structures that make up the eye are protected from the entry of dirt, bacteria and dust by a transparent mucous membrane called the Conjunctiva. It is a durable, resilient membrane which provides vital protection of the sensitive eye underneath however occasionally you may notice redness, swelling and secretions from this area, this may be a condition known as Conjunctivitis.

What is conjunctivitis?

Conjunctivitis is the inflammation of the membrane called the conjunctiva which covers the front of the eye and lines the eyelids. Although this condition is not life threatening the eyesight is an important sense and as such you should consult your veterinary practice as soon as possible if you suspect conjunctivitis. Mild cases can easily be treated at home and where an infection or abnormality is present your vet can advise the best course of action. Conjunctivitis can be caused by any of a number of factors; it can be in only one eye (unilateral) or in both eyes (bilateral). The cause may be a foreign body, bacteria, fungus or virus which enters the membrane and trigger’s the inflammation or it could be the result of an anatomical abnormality which is causing irritation in the eye. It is characterised by red, swollen tissue where fluid accumulates causing the third eyelid to be seen to cover part of the eye, it will be visibly pinky/red hence you may hear it referred to as “pink eye”. Many cases are accompanied by some form of discharge from the eye; the type of discharge is an indicator of the cause of the inflammation. A thin, watery discharge (known as serous discharge) is likely to indicate an allergy or foreign body irritant whereas a mucousy (mucoid) or pus like (purulent) discharge can indicate the presence of an infection, virus or an underlying condition. This information is extremely useful for your veterinary surgeon when examining your dog. Conjunctivitis is extremely uncomfortable; it can be itchy and can also be painful. You may notice your dog is agitated and stressed; he may rub his eye on the carpets, furniture and even your leg! It is a good idea to be extra cautious with a dog who is displaying such irritation as even the mildest mannered dog can become snappy or upset with such an uncomfortable condition.

Signs of conjunctivitis

With cases of conjunctivitis the first thing you are likely to notice is an abnormal appearance to one or both of your dog’s eyes. The condition is characterised by a red, swollen, moist looking eye and it may be that your dog shows a change in behaviour, he will likely be extremely irritated by the inflammation and may paw and scratch at their eye. Each case is different and you may notice any one or a combination of the following signs:

• Blinking excessively or squinting with one or both eyes
• Redness to the membrane covering the eye/ third eyelid
• Eye(s) may be closed
• There may be a discharge which can be
• Clear known as serous
• Pus known as purulent
• Mucous known as mucoid
• The dog may rub his eye on surfaces around the home
• Accompanying symptoms – Nasal discharge, sneezing, coughing

Causes of conjunctivitis

Conjunctivitis can occur in dogs of any age, it is commonly seen in puppies as they begin to open their eyes. There are a wide range of possible causes; although none are life threatening it is important that you visit a veterinary surgeon as soon as possible in order to avoid complications.

Any of the following can be a cause of conjunctivitis:

• Bacterial infection
• Fungal infection
• Viral infection ( such as distemper)
• Irritants such as chemicals, dust, cigarette smoke, shampoo
• Keratoconjunctivitis sicca (KCS) – dry eye where the eye produces inadequate tears
• Trauma to the eye or a foreign body.
• Follicle formation – small bumpy accumulations of cells on the eyelids which are a result of an immune response.
• Glaucoma – a condition where the pressure in the eye is increased.
• Abnormalities to the eye structure
• Breed predispositions ( long narrow faced breeds)

Diagnosing conjunctivitis

If you suspect a case of conjunctivitis you should make an appointment to see your veterinary surgeon although some very mild cases can be treated at home it is sensible to confirm a diagnosis. The type of discharge is an indicator of the cause of the conjunctivitis, should the discharge and redness be localised to only one eye (unilateral) it would suggest a foreign body. When it occurs in both eyes, a mucousy discharge will often indicate a bacterial, fungal or KCS cause, this can be so thick it can cause the eyelids to stick together. A clear water-like discharge however normally indicates an allergy or irritant while pus which normally forms crusts on the eye is generally caused by the bacteria Streptococcus or Staphylococcus. This visual reference can help for the vet reach a diagnosis and indicate any further tests that should be carried out.

In the case of a mucoid discharge the vet will likely carry out the Schirmer Tear Test – this identifies whether there is adequate tear production by using a small strip of filter paper placed on the eyelid for 60 seconds. It is a harmless, painless test and can identify Keratoconjunctivitis sicca (KCS).

It is likely that in order to rule out any damage or ulceration to the cornea that the vet will also carry out a test called a Fluorescein Stain. An orange dye is dropped into the eye and rinsed out with an eye wash, The vet then examines the eye with a light. Any damaged areas are stained green; this test also shows whether the tear ducts are functioning correctly.

In some cases the vet will take a scraping to identify the bacteria or fungus present however this is not normal practice.

Treatment of conjunctivitis

The treatment regime chosen by your vet will largely depend on the severity of the conjunctivitis. A case of serous conjunctivitis may only require bathing and monitoring. Your vet may recommend a branded eye wash or solution which can be used safely and regularly on your dog. If the cause is an allergy your dog may be prescribed a short treatment of anti-inflammatories or anti histamines. Bacterial infections will be treated with a combination of antibiotic eye ointment and oral antibiotics, similarly fungal infections will be treated with anti-fungal ointment.

Where an abnormality to the eye is found there may be an option of corrective surgery. Your veterinary surgeon can discuss the risks and benefits of surgery for each individual case.

If your vet identifies KCS it is likely your dog will be prescribed either artificial tears or an ointment which acts on the immune system to prevent deterioration of the tear glands and stimulate tear production. These are long term treatments that can help your dog feel more comfortable.

Prevention of conjunctivitis

There is no guaranteed way to prevent your dog from getting conjunctivitis but a few sensible precautions can minimise the chances of future cases. It is important to keep the eyes clean, using a soaked cotton pad with plain warm water is sufficient to keep your dog’s eyes free from discharge or irritants. Keep your dog away from potential allergens and irritants such as dust, smoke and grass seeds to prevent eye irritation or possible foreign bodies. It is advisable that in cases of eye problems due to conformation abnormalities that the dog is not used for breeding in order to prevent passing on the faults.