What is conjunctivitis?
Conjunctivitis is the inflammation of the conjunctiva. The conjunctiva is the thin semi-transparent mucous membrane lining the inside of the eyelids, covering the third eyelid. This membrane attaches to the globe of the eye at the level of the sclera (the white part of the eye). The back end of the word conjunctivitis (– itis) refers to inflammation which is a defense mechanism of the body and means swelling, redness, increased heat to the local area because of an increase in blood flow to the affected area, and pain or discomfort. Conjunctivitis is a very common condition affecting our household cats.
What causes conjunctivitis?
This condition is typically caused by infectious organisms such as viruses like Feline Herpes Virus or Feline rhinotracheitis virus or bacteria such as Chlamydophila Felis or Mycoplasma. Other causes can include trauma to the eye which most cats typically sustain through cat fights, immune-mediated conditions where the body overreacts to a stimulus and ends up causing more damage to itself, or sun damage especially in white cats with unpigmented eyelid margins. Infectious causes of conjunctivitis are the most common and are important to treat, but more importantly prevent, as the infection may spread from one cat to another. Infectious conjunctivitis is usually a condition affecting younger cats. Cats that may be at increased risk for infectious conjunctivitis include those that live in multi-cat households, cats taken to the kennels or a cattery, cats exposed to other sick animals at the vet, or free-roaming cats that come into contact with all the neighbourhood’s cats. Another risk factor for this condition is the presence of an underlying immunosuppressive condition such as FeLV (Feline leukemia virus) or FIV (Feline Aids) which predisposes affected cats to these infections due to their reduced ability to fight off infections.
Cancer of the conjunctiva more commonly affect older cats, typically cats with no pigment in their eyelid margins. Their eyelids are effectively sunburnt and the process starts off with inflammation of the eyelids causing conjunctivitis, and eventually progresses to full blown cancer. If sun exposure can be restricted or contained, this condition can be prevented.
What are the clinical symptoms of conjunctivitis?
Clinical signs may vary in degree and affect one or both eyes. Your cat may have painful red eyes, some discharge from the eye which may be either watery or pussy in later stages of the disease, and in severe cases the eye may even be closed due to excessive swelling of the conjunctiva. These signs may be recurrent and vary with severity during the course of the disease. With infectious causes such as viruses there are often signs and symptoms of other upper respiratory tract infections such as sneezing, discharge from the nose and a loss of appetite partly due to a loss of smell.
How is conjunctivitis diagnosed?
Conjunctivitis is diagnosed by the veterinarian carefully examining the eye and all its adjacent structures and looking at all the different parts of the eye. What vets often look for is the presence of red inflamed conjunctiva, discharge from the eyes, signs of trauma or potential causes of the inflammation. If a cat with conjunctivitis is presented to the vet, the vet may do certain tests to check other parts of the eye such as the cornea, tear duct function and even eyeball pressure. This is important to rule other eye conditions which also have conjunctivitis as a symptom, but requires a completely different approach to treatment. These tests include a fluorescein dye test, where a luminescent green dye is applied to check for any defects or ulcerations of the cornea (the glassy clear layer on the front of the eyeball through which the animal looks). Another test is the Schirmer tear test that checks the tear production and determines if your pet suffers from dry eye. Lastly, the vet may want to test the eye’s pressure to determine if glaucoma may be present. Glaucoma is a condition of increased pressure within the eyeball, causing gradual loss of sight. On some occasions, if treatment is not working, more in-depth procedures such as blood tests, biopsies and conjunctival samples for bacterial growth may be necessary to determine the underlying cause of the conjunctivitis.
How is conjunctivitis treated?
The treatment goals for any case of conjunctivitis in cats include treating the underlying cause, eliminating infection (if present/possible), and reducing pain and discomfort. If there is an underlying cause that has been identified, this will be treated. Generally the treatment entails eye drops that need to be given at home according to the vet’s instructions. On this note something many of us are guilty of is trying to self medicate our cats with human over the counter eye drops. This is not a good idea as some human medications are contra-indicated in cats and by using the wrong medication we can actually do harm and make the condition worse. Always seek the advice of the vet before applying any medication. This also applies to eye drops prescribed by the vet previously or to another animal in the house hold. If the eye medication contains cortisone and there is ulceration on the cornea, it will only worsen the ulcer and your animal may lose its eye.
What is the prognosis if my cat has conjunctivitis?
The prognosis of conjunctivitis is generally good but depending on the cause of the conjunctivitis, certain complications may arise. Infection with herpes virus may lead to a corneal sequestrum, symblepharon (partial or complete adhesion of the eyelid conjunctiva to the eyeball conjunctiva), or dry eye. These conditions are permanent and the cat will never recover fully if complications like these arise. Conjunctivitis may be recurrent or chronic in some cases of infections. Because cats with herpes virus are often chronic carriers it is important to reduce stress in the environment as that is often the trigger for recurrent infections. Cats with underlying Feline Leukemia Virus (FeLV) or Feline Aids Virus (FIV) cannot be cured and because of their compromised immune systems, will always be prone to complications. Because of the recurrent nature of conjunctivitis in certain cats please do not lose faith in the vet or his or her ability to treat your cat. Work with the vet to understand the specifics of your cat’s condition and if the condition cannot be cured with a once off treatment, work out a strategy with the vet to manage the condition as effectively as possible. As with all medical conditions in pets, the sooner you attend to the problem once you notice any symptoms of conjunctivitis in your cat, the higher the likelihood of success with treatment. Don’t leave it till the cat can hardly see from its eyes and only then try and do something about it.
Is there a way to prevent conjunctivitis in my cat?
The answer is an unequivocal YES! By far the most effective way to prevent your cat from getting conjunctivitis is to have it vaccinated at the correct intervals and with the correct vaccines to prevent the upper respiratory tract diseases collectively known as “Snuffles”. Is it fool proof and will vaccination definitely prevent your cat from contracting these diseases? The answer is no. Sometimes viruses mutate or different strains infect your animal to what was in the vaccine. Does this mean that vaccinating is “fighting a losing battle”? Not at all. Having your cat vaccinated is certainly the best way to prevent disease, but does not guarantee that they won’t get infected. Making plans with cats who roam and land up in fights is a tough task, but can be done when there is a will to do so. Keeping cats with unpigmented eyelids indoors and out of the sun, is also a tough task because cats are by nature so inquisitive. Yet, if is means a better quality of life, cancer free, it is a small price to pay. Discuss your cat’s particular circumstances with the vet and find a solution with professional help.
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