Multiple Ocular Defect (MOD) is a recently identified hereditary eye disease affecting Old English Sheepdogs, among other breeds. MOD causes a variety of ocular abnormalities, including some non-congenital cataracts and retinal dysplasia, which can lead to significant vision loss and, in severe cases, may require eye removal.
Researchers at the University of Cambridge have identified MOD as being caused by a change in the COL11A1 gene, which affects the production of collagen, a key component that helps maintain the structure and function of the eye. This mutation is passed on in an autosomal dominant manner, meaning that any dog with one or two copies of the mutated gene is likely to develop the disease at some point in its life. Early detection through a genetic test, developed by the research team, is crucial for breeders to make informed decisions and help prevent the spread of MOD in future generations.
Old English Sheepdogs affected by MOD can exhibit various eye anomalies, which vary in type and severity depending on their genetic status (heterozygous or homozygous). The most common symptoms include:
MOD often causes hereditary cataracts, which make the lens cloudy and reduce vision. Other issues with the lens include microphakia (a smaller-than-normal lens), macrophthalmos (enlarged eyes), and spherophakia (a rounder-than-normal lens). Sometimes, a defect called coloboma can occur, creating gaps in the lens or other parts of the eye. These abnormalities can further affect the dog’s ability to see clearly.
In Old English Sheepdogs with MOD, the retina may develop abnormal folds, which can interfere with normal vision. In more severe cases, the retina can detach from the back of the eye, leading to significant vision loss or blindness. Additionally, the vitreous humor, the gel-like substance between the lens and the retina which helps the eye maintain its shape, can break down or develop other problems, making vision worse. Inflammation in the eye, called uveitis, can also occur and add to the complications.
During a puppy’s eye development, blood vessels nourish the growing lens. Normally, these vessels disappear after birth, but in some cases, they persist. While PPM can occur independently of MOD and is often harmless, in dogs with MOD, persistent pupillary membranes may be one of several eye abnormalities. In these cases, the remaining blood vessels can obstruct vision or induce cataracts and contribute to other complications associated with the disease.
Not all affected dogs will show every symptom, but the ocular defects associated with MOD can significantly impair vision and cause discomfort. In some cases, inflammation of the eye, known as uveitis, may develop as a complication of cataracts, further aggravating the condition. Secondary glaucoma, which can arise from these abnormalities, may increase intraocular pressure, leading to further eye damage and pain. Regular monitoring by a veterinary ophthalmologist is crucial for managing these complications when possible.
It’s important to note that Iridocorneal Angle Abnormality (ICAA) and congenital cataracts are not part of Multiple Ocular Defect (MOD). Researcher of Cambridge believe that congenital (present at birth) cataract is a seperate condition and set the cause yet as unknown.
MOD follows an autosomal dominant inheritance pattern, meaning that a single copy of the mutated gene is enough to cause the disease.
Dogs with two copies of the mutation will pass it on to all of their offspring. These dogs tend to experience more severe symptoms due to the presence of both copies of the defective gene.
Dogs with one copy of the mutation have a 50% chance of passing it to their offspring. Although these dogs will develop MOD, their symptoms may be milder, often with a delayed onset compared to homozygous dogs.
To minimize the occurrence of MOD and prevent the production of affected dogs, breeders should prioritize mating dogs that have been tested and are free of the COL11A1 mutation. This practice is critical for reducing the prevalence of the disease within the breed. In addition to testing for MOD, breeders should conduct annual checkups for hereditary eye conditions, including a standard eye exam and gonioscopy, until the dog reaches six years old. Responsible breeding practices are key to safeguarding future generations from MOD and other genetic eye disorders.
Researchers at the University of Cambridge have developed a genetic test that accurately detects the specific mutation in the COL11A1 gene responsible for MOD in Old English Sheepdogs. This test helps breeders and veterinarians determine whether a dog carries one or two copies of the mutation, or if it is mutation-free. Although several labs offer the DNA test, ordering it directly from Cambridge supports their ongoing research efforts. You can order your kit here: Cambridge Animal Genetics.
The prognosis for MOD largely depends on whether the dog carries one or two copies of the mutation. Dogs with two copies (homozygous) often experience more severe symptoms and a faster progression, while those with one copy (heterozygous) may have milder symptoms.
Managing MOD requires regular veterinary ophthalmologist check-ups to monitor the disease and address complications like glaucoma. Treatment may include medical therapy, such as eye drops, or surgical options (for cataract) to reduce intraocular pressure. In severe cases, enucleation (eye removal) may be necessary to relieve pain and prevent further issues.
Since 2024, many breeders have tested their dogs for Multiple Ocular Defect (MOD), greatly reducing the chances of passing on the disease caused by the COL11A1 gene mutation. This testing has made it easier to breed healthy dogs and prevent affected offspring. However, MOD is not the only hereditary eye condition in Old English Sheepdogs. Other genetic eye disorders, such as hereditary cataracts, still exist, and MOD testing alone won’t detect them. To ensure comprehensive eye health, ECVO recommends breeders to conduct annual eye checkups and gonioscopy every three years, until the dog is 7 years old. This proactive approach helps catch other hereditary conditions early and promotes responsible breeding.