May
27
Written by:
Surgi-Care Center for Horses
5/27/2011 4:52 PM
Corneal ulcers are a very
common ocular problem in the horse, usually resulting from trauma to the eye.
The cornea (the clear, front part of the eye which covers the iris and the
pupil) is approximately 1-1.5 mm thick in the center and 0.8 mm thick around
the edges and is made up of three layers; the epithelium, the stroma (composed
of collagen), and Descemet’s membrane (inner endothelial layer). Trauma to the
cornea can result in disruption of all or some of the layers. An intact corneal
epithelium prevents infection from entering the eye. The tear film is
constantly removing debris from the surface of the eye. Once the epithelium is disrupted,
infection by microorganisms can occur.
Clinical signs of corneal
ulceration include squinting (or holding eye closed), rubbing, tearing, redness
or swelling of the conjunctiva (the membrane that covers the white part of the
eye and lines the inside of the eyelids), and cloudiness of the cornea. If your
horse exhibits any of these signs, contact your veterinarian immediately. All corneal
ulcers in the horse are considered an emergency. Corneal ulcers are diagnosed
by staining the eye with a fluoroscein stain to determine if the epithelial
layer of the cornea has been damaged. A blue light is directed at the eye and
any defects in the cornea will take up the stain and appear green. A culture of
the affected area may also be performed in order to identify bacteria or fungi
present in the ulcer. This information is helpful in choosing appropriate
antimicrobial drugs to control the infection.
Corneal ulcers should
always be treated aggressively, regardless of the size or depth of the ulcer.
Simple ulcers can be treated with antibiotic ointment (such as
bacitracin-neomycin-polymyxin) and atropine (which is used to dilate the pupil
and decrease pain caused by ciliary body spasms). Never use a triple antibiotic
with a steroid on a corneal ulcer! The steroid in the ointment will prevent the
ulcer from healing. Larger or deeper ulcers require more aggressive and more
frequent treatment, which may include multiple antibiotic and antifungal
solutions. Serum from the horse’s blood is often used to prevent the cornea
from melting and to help stimulate corneal healing. Banamine is also an
important component of the treatment protocol for corneal ulcers as it helps
reduce pain and inflammation in the eye.
If ointments are used to
treat a corneal ulcer, they should be administered 30 minutes apart. The
ointment can be applied to a clean finger and gently rubbed on the inside of
the lower eyelid. The Solutions should be administered 5 minutes apart and can
either be squirted into the eye using a syringe or through a subpalpebral
lavage system. A subpalpebral lavage system, placed in the upper or lower
eyelid, consists of a thin piece of silocone tubing extending from the eyelid
to the horse’s withers. The lavage system allows for medications to be
deposited directly onto the cornea without having to hold the horse’s eye open.
The subpalpebral lavage system can be in place for weeks while the corneal ulcer
is healing.
Corneal ulcers are true
emergencies. As in many cases, the sooner appropriate treatment is started, the
more likely a positive outcome is seen.
Always contact your veterinarian immediately if you suspect your horse
has had trauma to the cornea.
For
more information you may contact Surgi-Care Center for Horses at 813-643-7177
or by email lkuebelbeck@surgi-carecenter.com.