Page 1230 - Problem-Based Feline Medicine

1222 PART 15 CAT WITH EYE PROBLEMS

Allergic states caused by diet have been implicated. An elimination diet that changes the source of protein
Dietary exclusion tests may be useful to eliminate this as may identify a food allergy. Protein sources such as
a cause. (See The Cat With Miliary Dermatitis, page venison, duck, turkey, rabbit, kangaroo mixed with carbo-
1029). hydrate (rice, potato or pasta) are frequently used for
periods of up to 1 month for diagnosis of food allergy,
but a balanced commercial hypoallergenic diet is best
ALLERGIC CONJUNCTIVITIS*
for maintenance. WARNING: Vegetarian diets will
rapidly cause blindness by depleting taurine, and
Classical signs
should never be used in cats. They cause retinal degen-
● Mild serous discharge that may be eration and blindness as well cardiac problems (see The
intermittent and seasonal. Cat With Signs Of Large Bowel Disease, page 766).
● Very little pathology is evident in the
conjunctiva. Differential diagnosis
● Cats may sneeze.
Mycoplasma conjunctivitis can produce mild inflam-
See the main reference on page 17 for details (The Cat mation with serous discharge. However, it usually
With Acute Sneezing or Nasal Discharge). responds very well to a wide variety of antibiotics, com-
pared with a poor response in allergic conjunctivitis.
Pathogenesis Chronic feline herpes virus-1 conjunctivitis may pro-
duce chronic serous discharge with very little conjunc-
Allergic conjunctivitis is an uncommon problem in cats,
tival inflammation similar to allergic conjunctivitis.
and may be associated with an insect bite allergy (fleas
Use laboratory tests to differentiate, particularly PCR
and biting insects such as mosquitoes and midges), food
or virus isolation.
allergy or atopy (usually caused by pollens).
Treatment
Clinical signs
Topical corticosteroid drops used twice daily will usu-
Signs may be intermittent and seasonal, depending
ally control most cases with allergic conjunctivitis. The
on the allergen.
range of drops used can vary according to the severity
There is a mild serous discharge, and the cat may of the signs. Very mild cases will respond to 0.1%
show signs of irritation by rubbing its eyes. hydrocortisone drops, while more acute cases will
respond better to drops containing 0.5–1% pred-
There is usually very little conjunctival inflammation
nisolone acetate.
associated with this condition.
If a food allergy is diagnosed based on response to an
The may be concurrent sneezing, dermatitis and/or gas-
elimination diet, and reoccurrence of signs when
trointestinal signs.
challenged with the original diet, the cat should be
transitioned from the homemade elimination diet to a
complete commercial hypoallergenic diet for
Diagnosis
maintenance. Most homemade single protein and
There are no specific diagnostic tests for allergic con- carbohydrate source diets are not balanced, and are
junctivitis. It is usually diagnosed by eliminating other suitable only for a limited diagnostic trial, and not for
causes of conjunctivitis, and on the presence of a mild maintenance. Vegetarian diets will rapidly cause
serous discharge with very little inflammation in the blindness by depleting taurine and should never be
conjunctiva. used in cats.
Allergy testing done by a dermatologist may help iden- Where there is a confirmed allergy caused by atopy,
tify the allergen in cases with atopy. (See The Cat With food allergy or insect bites, exposure to allergens needs
Miliary Dermatitis, page 1031.) to be controlled as much as practicable. Prevent insect