Collie eye anomaly (CEA) is a genetic eye disorder that affects several dog breeds, including collies, Australian shepherds, border collies, Shetland sheepdogs, and Lancashire heelers. It is an inherited syndrome characterized by various eye problems that can lead to vision defects. While CEA is present from birth due to inherited DNA mutations, its symptoms, such as retinal folds and detachments, may appear after birth and may change over time. The severity of the disease varies among affected dogs, with some experiencing progressive eye issues.
Causes and Inheritance
CEA is caused by DNA mutations that result in improper development of the retina and/or choroid (the blood vessel layer under the retina) in the eye. The severity of the disease depends on the specific mutations and their impact on vision. The disease is inherited in an autosomal recessive manner, meaning that affected dogs must inherit two copies of the mutated gene, one from each parent. Dogs with one mutated gene are carriers and do not have the disease.
Diagnosis and Screening
CEA is typically diagnosed during eye screenings performed by a veterinary ophthalmologist when the dog's pupils are dilated. Responsible breeders of dog breeds affected by CEA should have their dogs screened for CEA before breeding. Genetic tests are available to determine if a dog is normal, a carrier, or affected with CEA with high accuracy. Even puppies can undergo genetic testing as long as they are large enough for a veterinarian to safely collect a blood sample.
Puppies should also be checked by a veterinary ophthalmologist at around 5-6 weeks old, preferably before 12 weeks. Eye exams should be done to determine which dogs should not be bred or should be bred with care to another tested dog. Selective breeding and genetic testing are helping to reduce the number of CEA cases worldwide.
Symptoms and Eye Problems
CEA can cause several eye problems, including:
- Choroidal Hypoplasia: A blood vessel layer under the retina fails to develop properly, leading to blind spots in vision.
- Retinal Detachment: Separation occurs between the retina and choroid, resulting in partial or complete vision loss in the affected eye. Retinal detachment can occur at any age.
- Coloboma: Focal cupping or bulging in the eyeball, often near the optic disc. Severe cases can be associated with blindness or retinal detachments.
- Retinal Folds: Folds inside the retina occur when it is too large for the eye. These folds may resolve with age.
- Vascular Defects: Abnormalities in eye vessels responsible for blood supply can lead to malformations or undersized vessels.
Management and Treatment
CEA has no cure, but some eye problems can be managed with surgery or other treatments. However, once the eyes are not properly formed, no cure is possible. The best approach is to prevent CEA through eye screenings and genetic testing in breeding dogs. Responsible breeding practices can help reduce the prevalence of the disease and ensure healthier offspring.
Collie eye anomaly (CEA) is a genetic eye disorder affecting certain dog breeds, characterized by various eye problems that can lead to vision defects. The disease is inherited in an autosomal recessive manner, and responsible breeding practices, including genetic testing and eye screenings, are essential to reduce its prevalence and prevent affected offspring. While there is no cure for CEA, early detection, screening, and selective breeding can help manage the disease and improve the quality of life for affected dogs.
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