What is a
The cornea is
the transparent, shiny membrane which makes up the front of the
eyeball. Think of it as a clear window. To understand a corneal
ulcer, you must first understand how the cornea is constructed.
cornea is comprised of three layers. The most superficial layer is
the epithelium. This layer is comprised of several very thin
layers of cells. Think of it in terms of the many layers of an onion
skin. Below the epithelium is the stroma, and the deepest
layer is Descemet’s membrane. Because all of these layers of
the cornea are clear, it is not possible to see them without special
stains which color particular cells and highlight them when looked
at with an ophthalmoscope.
Erosion of a
few layers of the epithelium is called a corneal erosion or
corneal abrasion. A corneal ulcer is an erosion
through the entire epithelium and into the stroma. If the erosion
goes through the epithelium and stroma to the level of Descemet's
membrane, a descemetocele exists. This is a serious
condition. If Descemet's membrane ruptures, the liquid inside the
eyeball leaks out, the eye collapses and irreparable damage can
does a corneal ulcer occur?
several causes of corneal ulcers in dogs. The most common is trauma.
An ulcer may result from blunt trauma, such as a dog rubbing its eye
on the carpet, or due to a laceration, such as a cat scratch.
Another common cause is chemical burn of the cornea. This may happen
when irritating shampoo gets in the eye.
causes of corneal ulcers include bacterial infections, viral
infections, and other diseases. These may originate in the eye or
develop secondary to disease elsewhere in the body. Examples of
other diseases include: Epithelial Dystrophy (a weakening of the
cornea which can be inherited in breeds such as the Boxer); drying
of the cornea due to abnormal tear production, called
Keratoconjunctivitis Sicca (KCS or “dye eye”); and diseases of the
endocrine system such as diabetes mellitus, Cushing’s Disease (hyperadrenocorticism),
does a corneal ulcer affect my dog?
A corneal ulcer
is very painful. Most dogs rub the affected eye with a foot or on
the carpet in an attempt to relieve this intense pain. To protect
the eye, they keep the lids tightly closed. Occasionally, there will
be a discharge that collects in the corner of the eye or runs down
is a corneal ulcer diagnosed?
corneal abrasions are usually not visible. They can be visualized
with the use of special stains such as fluorescein. A drop of this
stain is placed on the cornea. The dye will adhere to an area of
ulceration and is easily seen using special ophthalmic lights. This
is the most common eye test performed and may be the only test
needed if the ulcer is acute and very superficial. If the ulcerated
area is chronic or very deep, samples are taken for culture and cell
study prior to applying the stain or other medication.
is a corneal ulcer treated?
depends on whether there is a corneal abrasion, corneal ulcer, or
abrasions generally heal within 3-5 days. Medication is used to
prevent bacterial infections (antibiotic ophthalmic drops or
ointment) and to relieve spasm and pain (atropine ophthalmic drops
or ointment). Antibiotic drops are only effective for a few minutes
so they must be applied frequently; ointments last a bit longer but
still require application every few hours. It is suggested that an
antibiotic preparation be instilled in the eye every 4-8 hours. On
the other hand, the atropine lasts many hours so this drug is used
every 12 to 24 hours.
If a corneal
ulcer or descemetocele is present, measures must be taken to protect
the eye and to promote healing. Since dogs do not wear eye patches
well, surgery is often used to protect the injury and allow for
normal healing. Other surgical procedures include removal of dead or
poorly healing cornea, corneal grafts and more. There are several
surgical techniques available. Your veterinarian will choose the
best surgery to ensure rapid healing for your pet.
a corneal abrasion become a corneal ulcer?
After 2-3 days
of treatment, your dog should be re-examined to determine if proper
healing is occurring. If not, surgery may be recommended for your
there any side-effects from the eye medications?
dog will be allergic to an ophthalmic antibiotic. If your dog seems
to be in more pain after the medication is used, discontinue it and
contact your veterinarian immediately.
A corneal ulcer
is extremely painful so the eye is kept tightly shut. Atropine
relieves the pain but also dilates the pupil widely. Therefore, the
eye is very sensitive to light and many dogs will squint or close
the eye when exposed to bright light.
The effect of
atropine may last for several days after the drug is discontinued.
Do not be alarmed if the pupil stays dilated for several days.
dog began to drool excessively and paw at its mouth after I
administered the eye medications. Is that a reaction?
No. The tear
ducts carry tears from the eyes to the back of the throat. The eye
medications may go through the tear ducts and eventually get to the
throat where they are tasted. Atropine has a very bitter taste,
which may cause drooling, and pawing at the mouth. You are seeing
your dog's response to a bad taste, not a drug reaction.
a corneal ulcer is painful, can I apply a topical anesthetic to the
anesthetic is often used to numb the cornea so the diagnostic tests
may be performed. However, these drugs often delay healing and
should be used with discretion.
do I know when to discontinue medication?
The best way to
tell that the cornea has healed is to repeat the fluorescein stain
test. This will be performed by your veterinarian 5-7 days after
treatment has begun.
appear to be some red streaks near the ulcer. Is that normal?
cornea has no blood vessels in it. However, when a corneal ulcer or
descemetocele occurs, the body tries to heal by growing new blood
vessels through a process called neovascularization. The new
vessels begin at the sclera (the white part of the eye) and cross
the cornea to the ulcer.
is a good response because it indicates healing. However, after the
ulcer is healed, these vessels remain in the cornea. They are not
painful, but they do obstruct vision. Therefore, it is desirable to
remove them. This is done with the use of ophthalmic drops or
ointment containing a corticosteroid, which may be used for a few
days to several weeks, depending on how much neovascularization is
is important that steroids are not used in the eye too soon because
they will stop the healing process and may cause complications.
Therefore, the fluorescein dye test should be performed before
beginning this type of medication. If steroids are used and the eye
becomes painful again, discontinue the steroids and contact your