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Ophthalmology
PREVENTING EYE DAMAGE
KCS OR “DRY EYE”
b
h
a
g
f
e
d
c
conjunctiva: membrane lining the eyeball
and eyelid (a)
sclera: tough, white, outer coat of the eyeball (b)
cornea: transparent “window” of the eye (c)
h
Adequate production of tears to cover the outer surface of the cornea is essential to good ocular health. Tears supply nutrients, moisture and lubrication to
the cornea, flush debris from the surface of the cornea, enhance vision and
help to prevent infection.
pupil: open center of the iris through which
light passes (d)
iris: colored, contractile membrane that regulates opening of the pupil (e)
lens: transparent body that focuses light rays
on the retina (f)
Veterinary ophthalmology deals with
anatomy, function, pathology and treatment of the eye in all species of animals.
If your animal shows subtle or obvious
signs that could indicate eye disease,
early diagnosis and treatment by your
veterinarian or veterinary ophthalmologist
is the key to maintaining vision
and comfort.
Keratoconjunctivitis sicca (KCS) or “dry eye” is a common ocular disorder
that affects the cornea and conjunctiva of dogs and, less commonly, cats.
If tear production falls below a critical level, the conjunctiva and cornea
can rapidly become ulcerated and pigmented. KCS is relatively easy to
diagnose and usually responds favorably to long-term medical therapy.
Left untreated, KCS can lead to permanent eye damage or blindness.
Some of the many causes of inadequate tear production are genetic
predisposition, immune-mediated disorders, side effects of certain
drugs, and some systemic diseases.
FINDING THE ROOT OF THE PROBLEM
HYPERTENSIVE RETINOPATHY
Older cats may develop iris hemorrhage or
retinal hemorrhage, edema or even detachment
as a result of high blood pressure. Discovery and
management of kidney disease or hyperthyroidism
may reduce blood pressure and restore vision.
Even if hypertension alone is suspected, once
blood pressure is lowered toward normal levels,
reassessment using laboratory tests such as blood
urea nitrogen (BUN), creatinine, and urinalysis
may reveal kidney problems that were not obvious.
Your veterinarian plays a key role in early recognition and management of KCS to prevent pain and visual impairment. Diagnosis is
based on clinical signs and is confirmed by measuring tear production. The procedure is inexpensive, painless, reliable and can be performed in the exam room.
IRIS HEMORRHAGE MAY BE DUE TO
HYPERTENSION, ESPECIALLY IN OLDER
CATS. BLEEDING FROM THE IRIS OR
RETINA IS SOMETIMES THE FIRST SIGNAL
AN ARTIFICIAL LENS MAY RESTORE VISION
THAT BLOOD PRESSURE IS ABOVE NOR-
TO AN ANIMAL WITH CATARACTS SUCH
MAL, AND MAY ALSO INDICATE KIDNEY
AS THIS DOG (IMMEDIATE LEFT). AFTER THE
OR THYROID PROBLEMS.
OPAQUE NATURAL LENS IS EXTRACTED
FROM THE ANIMAL’S LENS CAPSULE, THE
vitreous humor: clear, gelatinous
FELINE HERPESVIRUS
by the optic nerve to the brain (h)
SIGNS, DIAGNOSIS AND TREATMENT
THE ABOVE CT IMAGE SHOWS A
DOG WITH AN INFLAMED SALI-
Orbital disease often reflects the presence of a mass such as a
tumor, an infected area or inflammation within the orbital space.
VARY GLAND BENEATH THE EYE
An early clinical sign of orbital disease is the altered appearance of your pet’s eye,
especially more of the white (sclera) being exposed, because swollen tissues cause the eye to protrude.
Other signs include difficulty seeing, blinking or moving the eye, or altered pupil size or direction of gaze.
Initially, signs can be very subtle and require close examination by your veterinarian or a veterinary ophthalmologist. As the disease progresses, secondary signs include difficulty closing the eyelids and subsequent drying, inflammation, and ulceration of the cornea and/or conjunctiva. As with most diseases, early
diagnosis and treatment is likely to minimize discomfort and provide the best prognosis.
THE EYE TO PROTRUDE FROM THE
Infection or immune-mediated inflammation is usually treated with orally administered drugs, but surgical
removal of a cancerous mass may be required.
The Ophthalmology Service of the
Veterinary Medical Teaching Hospital—
with faculty members David Maggs,
Nedim Buyukmihci and Service Chief
Steven Hollingsworth; resident veterinarians
Stephanie Beaumont and Kathryn Good;
and registered veterinary technician (RVT)
Kelly Reynolds—provides care for clients and
referred animals of all species.
The ophthalmology faculty shares research
findings with the veterinary professional community, and provides education and advanced
training to veterinary students, graduate students, and residents preparing to become
board-certified ophthalmologists.
For more information, visit the American
College of Veterinary Ophthalmologists Web
site (www.acvo.com), visit the UC Davis
Veterinary Medical Teaching Hospital
Ophthalmology Service Web site
(www.vetmed.ucdavis.edu/vmth),
or
phone the service at (530) 752–1393.
ARMS T0 ANCHOR IT IN PLACE (FAR LEFT) IS
RESEARCHING NEW TREATMENTS
retina: light-sensitive membrane connected
Further diagnosis of orbital disease usually involves a thorough physical examination. Your veterinarian
may suggest some preliminary blood tests and a chest radiograph to test for cancer (neoplasia), and later
in the diagnosis computed tomography (CT), magnetic resonance imaging (MRI) or radiography may be
required for accurate assessment of the size and location of the mass. Biopsy—collection of a small tissue
sample for microscopic diagnosis by a board certified veterinary pathologist—may be required to determine the exact nature of the mass.
OPHTHALMOLOGY
AT UC DAVIS
PLASTIC LENS WITH DELICATE “SPRING”
substance (g)
ORBITAL DISEASE
TEACHING,
RESEARCH AND
PUBLIC SERVICE
(IN THE ORBIT). THE ENLARGED
GLAND (LOWER ARROWS) CAUSES
ORBIT (UPPER ARROW). MASSES IN
THE ORBIT, SUCH AS CANCERS
AND ABSCESSES, ARE RELATIVELY
UNCOMMON IN DOGS AND CATS.
Feline herpesvirus type 1 (FHV-1), a common viral infection of
cats, can affect the eyes and respiratory tract. Most cats are
first infected as kittens, but after symptoms clear, they remain
latently infected with the virus. Most latently infected cats rarely
have a problem, but some have recurrent disease episodes
throughout life. Signs of FHV-1 recurrence are conjunctivitis
(redness or swelling of the conjunctiva, squinting or tearing)
and/or keratitis (corneal cloudiness) or, sometimes, feline
eosinophilic keratitis (pink plaque over the cornea), dry
eye, symblepharon (fusion of conjunctival and corneal tissues) or corneal sequestration (black spot on the cornea).
In order to prevent such episodes, many cats need both
treatment and the reduction of stresses such as other
health problems, arrival of a new cat or puppy in the
house, pregnancy or nursing, or moving to a different
house. Antibiotic treatment is ineffective for FHV-1, but
some of the newer human antiviral drugs can be used to
reduce the frequency or severity of recurrences.
THE SCLERA BECOMES MORE
EXPOSED AS A DOG’S EYE
PROTRUDES DUE TO INFLAMMATION OF THE ORBITAL EYE MUSCLES. THE CONDITION IS USUALLY
TREATABLE WITH MEDICATION.
Professor David Maggs and post-graduate researcher
Heather Clarke carry out laboratory studies on the use of
human antiviral agents for cats. In association with nutrition specialists, they also study the effects of the amino
acids lysine and arginine on FHV-1.
IMPLANTED IN THE LENS CAPSULE (CENTER).
VETERINARY
OPHTHALMOLOGIST
RESTORING VISION
DAVID MAGGS AND
CATARACTS
RVT KELLY REYNOLDS
BULLETIN BOARD SERIES
Veterinary Medicine News
Vol. 19, No. 1, Spring 2002
OF THE VETERINARY
The lens helps to focus light onto the retina, where light energy is converted into electrical energy that can be interpreted by the brain. A cataract or lens opacity, which causes the pupils to appear white, blocks light to the retina,
sometimes resulting in vision loss. Depending on the cause, cataracts may or may not progress to total blindness.
OPHTHALMOLOGY
SERVICE AT UC DAVIS
EXAMINE THE FRONT
OF A DOG’S EYE
Cataract surgery is the most commonly performed elective surgery in humans in the United States. Cataract cases
are also common referrals to the Ophthalmology Service of the Veterinary Medical Teaching Hospital at UC Davis,
particularly for dogs, cats and horses.
USING A SLIT LAMP
BIOMICROSCOPE.
EVERY ANIMAL GETS
A COMPLETE EXAMINATION, FROM
EYELIDS TO RETINA,
TO ASSESS BOTH
VISION AND OCULAR HEALTH. A KITTEN WITH NORMAL
VISION IS ABLE TO
TRACK A TOY FISH
AS IT IS MOVED
BACK AND FORTH
DURING AN EXAM.
Cataracts are a leading cause of visual impairment in dogs, mostly due to inherited genetic defects. Sometimes
cataracts in dogs are associated with diabetes mellitus, advanced age, trauma or retinal disease. Early detection of
cataracts by your veterinarian may lead to blood and urine tests for diabetes. Cats are frequently presented to the
veterinarian for evaluation of painful, red eyes due to glaucoma (excess pressure in the eye), uveitis (inflammation
in the eye) or lens dislocation—all of which commonly result in cataracts. Horses may be born with cataracts, or the
condition may develop soon after birth. Like cats, adult horses typically develop cataracts secondary to uncontrolled
uveitis.
As part of the diagnosis, an ocular ultrasound and/or electroretinogram (ERG), which measures electrical activity
across the retinal cells when they are stimulated with light, may be suggested to test retinal function and check for
retinal detachment.
The only treatment currently available for cataracts that impair vision is surgical removal of the affected lens. Under
general anesthesia, the lens capsule is opened, the clouded lens material is fragmented and removed using ultrasound (phacoemulsification), and if possible, an artificial lens is implanted in the capsule.
A SEED, REVEALED BY EXAMINATION TO BE LODGED BEHIND THE
THIRD EYELID, IS REMOVED FROM A
GREAT HORNED OWL.