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MOON B L I NDN E S S
SIGNS TO LOOK OUT FOR:
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Excess tears
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Squinting
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Avoidance of bright light
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Redness and swelling of the
conjunctivae
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A small pupil
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A blue tinge to the surface or
inside the eye
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A white or red substance inside
the eye
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Rubbing the eye
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Surprise when approached from
one side
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Tripping over objects
Most horses with uveitis will initially present
with a sore eye. Unfortunately the signs
of uveitis are varied and can easily be
mistaken for other less severe causes of
ocular discomfort.
Prompt diagnosis and treatment by a veterinary
surgeon is essential if vision is to be saved.
If an infection is suspected, tests can be
carried out to determine the primary cause,
but normally treatment will commence before
results can be returned from the laboratories.
Treatment is aimed at controlling the
inflammation and eliminating the muscle spasm.
Unfortunately horses do not always appreciate
the application of eye drops several times per
day, and will quickly become head-shy once
feeling better. A sub-palpebral lavage catheter
(SPL) is a special piece of tubing (about 1
metre long) that can be surgically inserted
through an eyelid and sutured into place. The
remaining tube is then secured to a head collar
and allows topical eye drops to be injected
through it and onto the surface of the eye. If the
SPL is correctly placed it will sit comfortably
against the soft conjunctivae and does not
cause any irritation.
If the inflammation can be controlled the eye
will enter a 'quiescent phase' and will appear
to be comfortable once again. In cases of
ERU the time between bouts of inflammation
can vary and it is impossible to predict when
it will happen next.
A new treatment has been developed by
Professor Brian Gilger and his associates in
the USA. It involves the placement of an
implant into the tissues at the back of the eye.
The implant is a small disc impregnated with
a drug (cyclosporine) that is slowly released
into the eye. It has been demonstrated that a
single implant can last longer than 3 years
and will delay the progression of the disease.
The implant does not affect the horse's vision
and we have not seen evidence of discomfort
following placement at our centre.
Another surgical treatment that has successfully
been used involves the removal and
replacement of the gel (vitreous humor) that
holds the eye in its normal shape. This process
is designed to treat cases that are suspected
of being caused by a bacterial infection and
is more commonly used by veterinary
ophthalmologists in other parts of Europe.
Many horses are failed at pre-purchase
examinations due to the signs of ERU. It is
a costly disease to both the owner and the
horse and in the worst cases both eyes may
be affected. When treatment has not been
administered or failed to work, vision can
be compromised and the horse may not be
safe to ride, and in severe cases it can lead
to total blindness.
IN SUMMARY
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ERU is not a new disease
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Appaloosas and Warmbloods are
predisposed
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It is thought to be caused by multiple
factors
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It results in severe eye pain
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It is characterised by repeat episodes
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Inflammation leads to destruction of
the tissues of the eye
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Prompt veterinary attention is
required to prevent loss of vision
SUMMER 2011 ISSUE
EQUINE MATTERS
10
ERU degeneration of vitreous gel with fine white
strands seen through the pupil.
Sub-palpebral lavage catheter (SPL)
placement.
Cyclosporine implant prior to insertion.
Suitable eye protection to prevent repeat ERU.