Collie Eye Anomaly, also known as CEA, is an inherited
disease causing defects in the formation of the eye. CEA has
now been determined to be a genetic disorder.
Several forms of the disease are recognized, but the most
common is a lesion on the back of the eye called choroidal
hypoplasia (CH). All dogs affected by CEA have choroidal
hypoplasia, by definition. CEA is not a progressive disease
like prcd-PRA and most affected dogs may only have mildly
impaired vision. More severely affected dogs may have pits (colobomas)
affecting the retina and nearby tissues and in the most
severely affected eyes, retinal hemorrhaging and detachments
can occur, resulting in blindness.
Varying degrees of CEA and definitions are listed below:
Choroidal Hypoplasia, Chorioretinal Change, Choroidal
refer to abnormalities in the coloring or pigmentation of
the choroid or central layer of the eye's lining. This is
the most common abnormality found in CEA and all dogs with
CEA have CH. However it is the least harmful and mildest
form of CEA. Most dogs with this form function normally with
no ill-effects or loss of vision.
Ectasia, Staphyloma: While not completely
synonymous, these terms all refer to a cupping or bulging in
the eyeball usually in the area of the optic nerve.
Colobomas are the most common more serious complication of
CEA. Colobomas can be described as a pit in the eye or a
blister at the back of the eye that you can see with an
ophthalmoscope. Colobomas vary and can be small or large and
occur in approximately 25% of dogs with CEA.
Interestingly, you cannot have CEA without CH and won’t have
coloboma without CH.
A third set of complications which occur exclusively in dogs
with coloboma include retinal detachment or hemorrhaging in
the eye. About 5-10% of dogs with CEA have these severe
complications, which can lead to blindness. These
percentages are based on experience with the Collie Breeds.
Vascular Disease, Tortuous Blood Vessels: These
terms describe defects in the vessels of the eye, which are
responsible for its blood supply or "nourishment." These may
be malformed, undersized, or even lacking.
Retinal Detachment: Loosening
or separation of the innermost, or retina, layer from the
wall of the eye. This may involve a tiny area or the entire
retina. It can be either one or both eyes. The complete
detachment of the retina results in blindness in that eye.
There is usually no significant visual deficit with CH
or coloboma, but may lead to a blind spot in the eye.
These conditions usually do not affect the working
ability of a dog.
Fortunately, there is now a DNA test which will confirm
whether or not a dog is clear, a carrier or affected.