Collie Eye Anomaly (CEA), also known as Collie Eye Defect, is an inherited, congenital condition (present from birth) caused by a genetic mutation that disrupts normal eye development in the womb and after birth. This disruption leads to several abnormalities including small or sunken eyes, eye pain, and blindness.  In most cases this is not a progressive disease, but in some more severely affected dogs, complications can arise that can lead to worsening with age. Collie Eye Anomaly is a genetic condition that is passed down from parents to puppies. For a dog to actually develop the condition, it must inherit two copies of the faulty gene—one from each parent. If a dog only gets one copy of the gene, it won’t have any symptoms but can still pass the gene on to it's puppies if bred. These dogs are called "carriers. This type of inheritance is called autosomal recessive. Breeds that are genetically predisposed to CEA include Rough and Smooth Coated Collies, Shetland Sheepdogs, Australian Shepherds, Border Collies, Lancashire Heelers, Boykin spaniels, Long-Haired Whippets, Silken Wind-hounds, and Nova Scotia Duck Tolling Retrievers, as well as mixed breed dogs with Collie lineage. While CEA was once very common in Collies, with up to 90% of purebreds being carriers of the gene, selective breeding programs have greatly reduced its prevalence, though it remains a concern.

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With CEA, abnormal development of the inner layers of the eye can result in several different signs depending on which area of the eye is affected.  Some dogs may have normal vision, while others may experience vision loss or even blindness. Eye changes, including vision impairment, can range from mild to severe and typically affect both eyes, although one eye may be more severely impacted. Many dogs show no signs when mildly affected. The eyes can also appear abnormal, with some dogs showing microphthalmia (smaller than normal eyeballs), which can give the eye a sunken appearance. In some dogs the pupils may appear unequal, or dilated. In a minority of affected dogs, complications can develop including bleeding into the eye and/or retinal detachments - which can result in sudden blindness, a cloudy or red eye, pain, and even glaucoma (high-pressure inside the eye). Importantly, most of the changes of the eye seen with CEA are located at the back of a dog's eye, and so can only be identified by examination by a veterinary ophthalmologist. Partial or complete blindness can be caused by abnormalities in the optic nerve and layers at the back of the eye, or detachment of the retinas. Behavioral changes are often the most obvious indicator of vision problems. Behavioral signs of vision problems include:

• Decreased or unusual play activity.
• Hesitancy or refusal to go outside.
• Trouble finding toys or food/water bowls.
• Clumsiness, such as bumping into furniture or walls.
• Difficulty judging distances when jumping or trouble with stairs.
• Increased anxiety in new environments or around unfamiliar people or animals.
• Dogs can hide vision-loss in one eye extremely well, so sometimes there are no changes noticed by the owner when this occurs.

CEA is typically diagnosed by a veterinary ophthalmologist when a puppy is between 6 to 8 weeks old. Eye drops are administered into each eye, to dilate the pupils and make it easier for the vet to see the structures at the back of the eye. Then the vet uses an instrument to shine a light and magnify the structures in each eye revealing any abnormalities. The examination typically is carried out while the puppy is awake. The procedure is usually quick and painless. In some cases, additional diagnostic tests such as DNA testing or electroretinograms may be used to confirm the diagnosis and assess the severity of the condition. For breeds that are predisposed to CEA it is important to evaluate puppies prior to eight weeks of age as resolving retinal folds and/or pigment changes can occur, making it harder to accurately diagnose. In some cases, older dogs with vision problems can be diagnosed later in life. Genetic testing may be the only way to diagnose carriers, as they have no changes to their eyes. Abnormalities that can lead to a CEA diagnosis include:

• Choroidal hypoplasia: abnormal development of the blood vessel layer at the back of the eye is the most common change.
• Coloboma: a defect or hole in one of the eye structures, such as the optic disc, retina, choroid, or iris.
• Retinal folds, or creases in the retina: can indicate abnormal retinal development.
• Abnormal blood vessel formation: can lead to bleeding in the eye, glaucoma, retinal detachment, and blindness.
• Microphthalmia: smaller than normal eyeballs.

Unfortunately, there is no cure for CEA; however, treatment options are available to manage the condition and address specific complications:

• Laser Surgery: in cases where there is retinal detachment, laser surgery may be attempted to reattach the retina. This is most effective when detachment is detected early. Laser surgery can also be performed on a preventative basis if defects that predispose to retinal detachment are identified. Preventative laser surgery can reduce the likelihood of retinal detachment and help to preserve vision in affected dogs.
• Monitoring and management: regular eye examinations by a veterinary ophthalmologist are crucial to monitor the progression of CEA and detect any changes early. This allows for timely intervention if complications arise. Medical treatment can be used if complications such as bleeding in the eye or glaucoma arise to help manage these, usually involving anti-inflammatory or anti-glaucoma eyedrops.
• Supportive care: for dogs with significant vision impairment or blindness, supportive care and environmental modifications can help improve their quality of life. This includes maintaining a consistent environment, using tactile and verbal cues, and providing safe spaces for the dog to navigate.

CEA is a hereditary condition, so the best way to prevent it is through responsible breeding practices. Genetic tests are available to identify carriers of the CEA gene. Breeders should consult with their veterinarian to determine the appropriate pre-breeding tests. It is not recommended to breed two carriers of CEA to each other, because even if they are extremely mildly affected, there is a significant risk that their offspring will be affected - and their offspring could be much more severely affected than the parents. Breeding carrier animals also leads to the mutation being continuously passed down through generations. Ideally, even dogs with normal eye examinations should have genetic testing carried out if they are being considered for breeding.  

If your dog is diagnosed with CEA, work closely with your veterinarian to monitor their eye health. Regular check-ups with a veterinary ophthalmologist can help detect any changes early and manage any complications that may arise. Affected dogs should be examined by a vet as soon as possible if new changes are noticed, such as changes in vision or a red, cloudy eye. Your vet will guide you on the best ways to support your dog's vision and overall welfare.

Providing supportive care at home is essential for managing CEA and ensuring your dog leads a comfortable and fulfilling life. Here are some key aspects of home care:

• Regular eye check-ups: schedule regular eye examinations with your veterinarian to monitor the progression of CEA and detect any changes early. Early detection can help manage the condition more effectively and prevent complications.
• Safe environment: create a safe and familiar environment for your dog, especially if they have vision impairment. Avoid rearranging furniture and keep pathways clear of obstacles to prevent accidents. Use baby gates to block off hazardous areas such as stairs.
• Consistent lighting: ensure that your home is well-lit, especially in areas where your dog spends most of their time. Consistent lighting can help dogs with partial vision navigate their surroundings more easily.
• Training and commands: teach your dog verbal commands to help them navigate their environment. Commands like step up, step down, and stop can be useful for guiding your dog and preventing accidents.
• Mental stimulation: provide mental stimulation and enrichment activities to keep your dog's mind active and engaged. Puzzle toys, interactive games, and scent-based activities can help maintain cognitive function and provide a sense of accomplishment.
• Emotional support: offer plenty of love, patience, and reassurance. Dogs with CEA may experience frustration due to their vision challenges, so providing emotional support is crucial. Spend quality time with your dog and engage in activities they enjoy.
• Diet and nutrition: ensure your dog receives a balanced diet to support overall health. Consult your veterinarian for dietary recommendations that may benefit dogs with CEA.