The choroid is a vascular layer of the eye that supplies oxygen and nutrients to the retina, while the retina is the light-sensitive tissue responsible for forming visual images. In dogs affected by CEA/CH, the choroid may be underdeveloped (choroidal hypoplasia) and other structural abnormalities may be present, such as retinal folds or colobomas (localized defects in eye structure). These changes can vary widely in severity and may affect one or both eyes.
CEA/CH is a developmental condition, meaning the abnormalities occur before birth. In many cases, the severity of the condition remains stable throughout life, although secondary complications such as retinal detachment may occur in more severe cases, potentially affecting vision.
Clinical signs of CEA/CH can range from no visible symptoms to significant visual impairment, depending on the severity of the abnormalities. Many dogs with mild forms of the condition appear completely normal and maintain functional vision. In more severe cases, dogs may show reduced vision, difficulty navigating unfamiliar environments, or increased sensitivity in low-light conditions.
Because mild cases are often not outwardly visible, CEA/CH is frequently detected through routine veterinary ophthalmic screening rather than behavioral observation. Early diagnosis is especially important in breeding dogs to prevent transmission of the condition to future generations.
The eye examination for CEA/CH is performed by a veterinary ophthalmologist using specialized equipment such as a slit-lamp biomicroscope and indirect ophthalmoscope. These tools allow detailed visualization of the retina, choroid, and optic nerve. The examiner evaluates pigmentation, vascular development, and structural integrity to identify any abnormalities consistent with CEA/CH.
In addition to clinical eye testing, DNA testing for the NHEJ1 gene mutation is commonly used to confirm genetic status. This allows identification of clear, carrier, and affected dogs even before visible eye changes develop, making it a powerful tool for breeding programs.
Results are generally reported as:
- Clear (Normal): No mutation detected and no visible ocular abnormalities.
- Carrier: One copy of the mutation; typically no clinical signs but can pass the gene to offspring.
- Affected: Two copies of the mutation and/or visible eye abnormalities consistent with CEA/CH.
CEA/CH is particularly important in herding breeds and related populations, where the mutation is more prevalent. Routine screening of breeding dogs is strongly recommended to reduce the incidence of this inherited eye disorder in future generations.
For dog owners, early detection of CEA/CH allows for appropriate monitoring of vision and helps ensure safe environments for dogs with any level of visual impairment. While there is no treatment to reverse congenital developmental changes, many dogs with mild CEA/CH lead normal, active lives without significant vision problems.
The Collie Eye Anomaly / Choroidal Hypoplasia (CEA/CH) Health Test is an essential genetic and ophthalmic screening tool that supports early detection of inherited eye disease, responsible breeding practices, and long-term preservation of canine vision health.
