Eye Problems in Dogs and Cats
My-Dog.info > Dog Health
Frequently Used Diagnostic Tests, and Common Causes of Eye
Disorders
Eye problems are not uncommon in cats and dogs. To know what
is causing an eye (or the eyes) to be abnormal, your veterinarian
will take a full history, and closely examine the eyes for any
evidence of infection (bacterial, viral, or fungal), injury,
cancer, allergy, foreign material, or lumps/bumps/ingrown lashes
or eyelid deformities that might be irritating the eye, eye
surface or tissues in the socket.
An ophthalmoscope allows thorough visualization of the tissues
in the interior of the eyeball including the retina, the coating
that covers the back of the eye. Other more specialized equipment
such as slit lamp scopes allow for detailed evaluation of
hard-to-see areas such as the internal angle of the eye, that if
narrowed or blocked may lead to glaucoma, an increase in eyeball
pressure. Eyeball pressure can be directly measured using
tonometry, a piece of equipment that is placed directly on the
surface of the eye.
Sometimes the healthcare team will take a small amount of the
discharge or swab the tissues around the eye (conjunctival swab)
and examine the sample cells under the microscope (cytology), or
use a swab to obtain a sample to culture the discharge for
bacterial growth and antibiotic sensitivity to aid in their
choice of antibiotic therapy. The veterinarian may apply a dye,
or flush the tear ducts to assess their function. For conditions
of the cornea, topical dyes that fluoresce under ultraviolet
light may be applied to check for ulcer architecture. Eye
problems can have many causes, and sometimes more than one type
of problem co-exists. Discharge is not specific to any one cause.
Normal or Abnormal?
Some pets are prone to chronic (ongoing) eye problems because
of their breed-specific eye conformation. Short-nosed breeds such
as Persians and Pugs have very prominent eyes, and they can be
more prone to irritation by dust etc. because of their less
protected globe position. In many of these short-nosed breeds,
the tears tend to pool at the inside corner (medial canthus) of
the eye, and lose moisture there. The pooling is a combination of
conformation of the eye/eyelids, and a tear duct conformation
that does not allow adequate tear drainage into the nose. More
tears are often produced on an ongoing basis also, in order to
keep the prominent eyes moist. Pooling often results in a
porphyrin (pigment)-stained discharge that is sometimes pink,
red, sometimes brown, or even can appear black and crusty on the
fur. This is particularly noticeable in light-coloured pets, for
example, white poodles.
Sometimes a discharge is related to blockage or narrowing of
the tear ducts, and other times the eye problem relates to lack
of adequate tear cover over the surface (cornea) of the eyes
leading to dry eyes. Conditions such as pannus, a corneal pigment
and blood vessel outgrowth condition, or dry eye
(keratoconjunctivitis sicca) are examples of conditions that
relate to exuberant inflammatory responses. A tear production
test (Schirmer tear test) is typically used if dry eye is
suspected to help quantify tear flow. A small paper strip is
placed in the corner of the eye and the moisture wicks onto the
strip to provide a measure of the number of millimetres of tears
produced during timed trials.
Cataracts are opaque lenses that may develop due to genetics,
old age, diabetes and many other causes. In very senior pets,
they are considered a normal aging change if they develop in a
pattern typifying the old age cataract.
Treatments for Eye Conditions
Because of the diverse causes of eye problems, treatment
varies considerably—from surgery to topical or oral therapy.
Lubricating or antibiotic eye ointment or drops will often be
prescribed. Sometimes, if an allergic component is identified, a
soothing steroid component may be added to the treatment regimen.
Allergic eyes are an attractive place for bacteria to move in and
colonize because the tissue defenses are weakened by the
inflammation.
If eye preparations are prescribed, it is important to stick
to the treatment schedule in order to optimize progress. This of
course, can be quite a challenge in some pets that do not enjoy
having things placed in their eyes! Make sure your health care
team gives you administration tips to help you achieve success.
Nursing care such as regular gentle cleansing of the eye area
with sterile salt solution or tepid clean water to remove
discharge is important to prevent dermatitis (skin inflammation
and infection) in the fur around the eye and eyelids. If
dermatitis around the eyes is already present, a petrolatum
jelly-based ointment (with or without antibiotics) may be
recommended to provide a slick barrier on the skin, so the
discharge crusts do not adhere, and further irritate the area.
Your veterinarian will customize the treatment regimen for
each individual patient, and often one or more follow-up
appointments are necessary to confirm that proper resolution of
the problem is taking place, and perhaps to adjust medication
protocols.
Reprinted with permission from www.animalhealthcare.ca
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