Friday, March 7, 2014

Feline Conjunctivitis

We commonly see cats come into the clinic with eye problems.  Most of the time it has to do with conjunctivitis (inflammation of the conjunctiva which is the lining under the eyelid and over a portion of the eye itself).  Especially in kittens, the swelling can be quite dramatic and in cases where it is not treated can lead to problems with vision.

Severe conjunctivitis
The first thing we try to determine is the cause of the inflammation.  Although there are a number of different causes, there are three causes that occur most frequently.  These are viral infections, bacterial infections, and allergies.  In many cases we may not get the exact diagnosis, but response to treatment gives us a good idea if we are on the right track.

An eye exam can help rule out things like eyelid conformation issues, foreign bodies, or trauma.  After this, staining of the eye may be performed which can show changes consistent with a viral infection (dendritic ulcers on the cornea) or other scratches.  Conjunctiva swabs may also be taken which in some cases can show evidence of bacterial infection when looked at under a microscope.  With recurrent or non-responsive cases further testing with blood tests to evaluate for certain infections may be performed.

The most common viral infection causing conjunctivitis is a herpes virus infection.  In addition to eye problems, other upper respiratory signs like sneezing or congestion may also be seen.  This virus is the same type of virus that causes cold sores in people and can stay dormant in the body for long periods of time.  During times of stress the virus can reactivate and cause clinical signs.  In mild cases, the signs typically resolve on their own in 7-14 days.  In more severe cases, anti-viral therapy may be needed.  This can vary from using lysine, which is an amino acid that interfers in the replication of the virus to more specific anti-virals that can be given either orally (famciclovir) or topically (idoxuridine).

Applying drops to a cat's eye
The most common bacterial infections are Chlamydia or Mycoplasma.  Again, in mild causes these may improve on there own over a few weeks.  In more severe causes antibiotics may be needed.  Both bacteria typically respond to a tetracycline based antibiotic.  These can be given orally or topically as well.  We can have problems with esophagitis with tetracycline drugs, so many veterinarians substitute with azithromycin.

If an infectious problem is not suspected and an allergy is more likely (seasonality to signs, irritants like smoke in the air), then topical anti-inflammatories are usually helpful (steroids).

Please let me know if you have any questions.