Collie eye
anomaly (CEA) is a disorder characterized by abnormal development of
the eye. It occurs predominantly in the collie breed, although it is
also seen in the Shetland sheepdog, the Australian shepherd and the
border collie. In some areas, it is estimated that up to 75 percent of
collies are affected by the disease.
In its mildest
form, minor changes occur in the choroid, which is the vascular layer
in the back of the eye. These changes have little effect on sight. CEA
affects the retina, the choroid, and in severe cases, the sclera and
optic nerve.
CEA is an
inherited disease and most of the eye lesions associated with CEA are
present at birth. But minor lesions may not be detectable on the eye
examination after three months of age, so collies intended for breeding
programs should be examined early at six to seven weeks of age.
Even dogs with
minor lesions should not be bred because their offspring may be
affected with more serious forms of the disorder.
CEA is a simple
recessive disorder. All affected animals have two genes for CEA;
therefore, both of their parents are either affected dogs or carriers.
What
to Watch For Most dogs with
CEA have no detectable changes in vision; however, if they have large
lesions, they may have visual defects.
Choroidal
hypoplasia (CH). This is the
inadequate development of the choroid, which is a thin layer of blood
vessels that deliver oxygen and nutrients to the retina.
Coloboma. Colobomas are
holes or craters in the posterior lining of the eye due to incomplete
development of the fibrous coating of the eye. Most colobomas involve
or are near the optic disk and are always accompanied by CH. Vision may
be normal with small colobomas, but it is usually decreased or absent
with large colobomas.
Tortuous or
twisted blood vessels in the retina
Retinal
detachment
with or without hemorrhage, which occurs in the most severe cases.
Detachments usually develop by 6 to 12 months of age. Dogs that develop
retinal detachments in both eyes are blind.
Diagnosis CEA is best
diagnosed at between six and 12 weeks of age. CEA is diagnosed based
upon the finding of any of the eye lesions described above.
The primary tool
used to diagnose CEA is indirect funduscopy. This test examines the
retina or fundus of the eye, which is the back portion of the interior
of the eyeball. It involves examining the retina through the pupil
using a lens and ophthalmoscope.
Treatment Currently, there
is no treatment for CEA. The major emphasis is placed on eliminating it
from affected breeds.
Home
Care and Prevention Dogs with only
choroidal hypoplasia or small colobomas do not need follow-up care.
Dogs with retinal hemorrhages and large colobomas may be re-examined in
two to three months to monitor for the development of retinal
detachments.
The disease can
best be prevented by breeding only normal dogs.
This article has been provided
courtesy of PetPlace.com(www.petplace.com),
the definitive online
source for pet news, health,and wellness information.
