Collie Eye Anomaly

Rhea V. Morgan, DVM, DACVIM (Small Animal), DACVO

BASIC INFORMATION pupils. It is common for entire litters of puppies to be examined at Description 6-7 weeks by a veterinary ophthalmologist. Collie eye anomaly (CEA) is abnormal development of the retina Examination at an early age helps to determine which puppies and the sclera (the white, firm, outer coating of the eyeball). CEA may potentially be used for breeding in the future and which pup- affects both eyes and occurs most often in rough and smooth col- pies may develop vision abnormalities. Early examination is also lies. It is also found in the Shetland sheepdog, Australian shep- important to identify all affected puppies. Puppies with only mild herd, Lancashire heeler, and border collie. choroidal hypoplasia may be hard to recognize by 10-12 weeks of Causes age, because mild hypoplasia lesions may fill in with pigment and CEA is inherited as an autosomal recessive trait. Dogs that inherit disappear from view. Although these puppies look normal (and are an abnormal gene from each parent (homozygous) will develop called go normals ), they are actually affected with CEA. CEA. Dogs that inherit an abnormal gene from only one parent A genetic test for CEA has also been developed that can iden- (heterozygous) will be carriers of the disease. tify affected, carrier, and normal dogs. The test is performed on a blood sample and is available from OptiGen (www.optigen.com ) . Clinical Signs The following lesions are components of CEA: TREATMENT AND FOLLOW-UP • Choroidal hypoplasia is the most common lesion of CEA and Treatment Options represents underdevelopment of a portion of the retina and its background layer (the choroid). Lesions of choroidal hypopla- No treatment exists for CEA. To date, no effective treatment is sia may range from small to large. They do not often affect available to prevent the retinal detachments associated with this vision. condition. Laser therapy may be tried for partial retinal detach- • A coloboma is a pit or hole in the back of the eye. It may affect ments, if they are discovered early. To eliminate CEA from collies the optic nerve as it leaves the retina or some nearby area. and other affected breeds, it is recommended that only normal ani- Small colobomas are not usually associated with vision abnor- mals be used for breeding. Because CEA is so widespread in the malities, but large colobomas may cause decreased vision and collie breed, homozygous normal dogs are hard to find. In collies, predispose the retina to detachment. it is common for dogs with only choroidal hypoplasia to be used • The retinal vessels may be tortuous in some dogs, meaning for breeding. Dogs with only the mildest form of the disease may that they twist and turn in an abnormal fashion. These vessel still produce puppies with more severe lesions, if they are bred to changes do not affect vision unless they predispose the eye to another affected or carrier dog. retinal hemorrhages. Follow-up Care • Retinal detachments can occur and may be partial or complete. Complete detachment results in total blindness, often by 6-12 With the exception of the development of a retinal detachment, months of age. CEA is not a progressive disease. Puppies at risk for retinal detach- • Retinal hemorrhages may occur spontaneously, or they may be ments may be monitored periodically. Notify your veterinarian if associated with retinal detachment. any decrease in vision is noted. Prognosis Diagnostic Tests Prognosis for puppies with choroidal hypoplasia or mild colobo- The diagnosis of CEA is made by examination of the retina using mas is good, because these lesions do not usually affect vision. an ophthalmoscope. Since most lesions of CEA are present at birth, Vision may be affected by larger colobomas. Retinal detachment CEA can be seen in puppies as early as 6 weeks of age. Retinal invariably results in blindness in the affected eye. Retinal detach- examination is facilitated by the application of drops to dilate the ment can occur in one or both eyes.