Microphthalmia and Ocular Dysgenesis in Dogs

Your dog’s eyes begin to develop in the first stage following fertilization and continue to form throughout the gestational period. A genetic or hereditary disease may lead to structural and/or functional defects that appear immediately at birth, or during another stage of the dog’s development. As with humans, dogs sustain ocular aberrations and visual weakness unilaterally or bilaterally (in one or both eyes), and in association with genetics, trauma, stroke, organ failure, untreated infection or systemic disease such as diabetes.  One such ocular disease ascribed to genetics is microphthalmia, a rare condition in which one or both eyes appear overly small and sometimes recessed, a condition known separately as enophthalmos. Often, dogs born with microphthalmia typically have a protuberant third eyelid. In some cases, dogs with microphthalmia and enophthalmos bear only cosmetic abnormalities, while others are significantly impacted by partial or substantial vision loss, including blindness. 

Regarding breed affiliation, the most severe cases of microphthalmia are associated with a specific coat pattern: merle coloring (or dapple) merged with a large amount of white fur.  These dogs have the striking appearance of two differently colored eyes. While possessing a unique beauty, this dogs are likely born blind and partially deaf.  Breeds most affiliated with ocular dysgenesis include Australian Shepherds, Collies, Shetland Sheepdogs, Corgis, Great Danes, and sometimes the very popular smaller breeds such as Chihuahuas, Pomeranians, and Cocker Spaniels. Despite size, age or breed, there is currently no treatment for canine microphthalmia.

Of course, when our beloved pets are diagnosed with a disease, we despair at the thought of he or she suffering, losing ability or function, and even the prospect of euthanasia. Please try to keep in mind that dogs do not rely as extensively on their sight as do humans; their most finely-honed senses are hearing and smell. Just because a dog’s eyes appear small does not mean that vision problems will be big.  Dogs who primarily enjoy life as a pet or companion animal will benefit from veterinary treatment, owner vigilance and care, and possibly some modifications to behavior and lifestyle. It goes without saying that a newly blind or visually challenged dog will benefit from your assurance, love and support. One final recommendation is to neuter or spay a dog to halt transfer of these hereditary conditions.

Ocular Dysgenesis is a term that encompasses vision impairments that lead to a slight to severe loss of vision in dogs, including partial or complete blindness. Microphthalmia occurs when a canine is born with an eye that is smaller than normal; this is a disorder related to development.

The two leading physical symptoms of microphthalmia include a third eyelid and small, recessed eyes. 

The condition may accompany other developmental defects, including problems with the cornea, anterior chamber, lens and/or retina. 

• Clumsy behavior
• Anxiety
• Bumping into well-known objects
• Inability to locate food or toys
• Loss of social behavior
• Excessive sleepiness
• Changes in the eye’s appearance
• Two differently colored eyes (upon birth)
• Blindness
• Partial vision loss
• Partial deafness

Types

Ocular dysgenesis is an umbrella term that refers to a variety of vision problems in addition to microphthalmia, such as:

• Iris coloboma
• Cataracts
• Detachment of the retina/lens
• Corneal defects

• Genetic/developmental
• Systemic diseases such as diabetes
• Organ failure
• Untreated infection
• Trauma
• Aging
• Medications

Your veterinarian will likely conduct a history of the dog, a physical exam to try and determine the possibility of vision loss.  To check for cause, there will be blood work, cerebral spinal fluid test, CT scan/imaging, and an ophthalmologic exam. The vet will be looking for any signs of infection, damage, or systemic disease. 

Between the small, deeply recessed eye/s, often differently colored eyes and bulging third eyelid, a dog suffering from microphthalmia and enophthalmos bears a look that veterinarians, particularly veterinary ophthalmologists (veterinarians specializing in disease and disorders of the eye), recognize. However, this “trifecta” of ocular insults rarely leads to a simple diagnosis. This young canine may also be suffering from supplementary defects, be secondary to disease, or the result of medication. For a sure diagnosis, you may be referred to a veterinary ocular specialist, referred to as a canine ophthalmologist.

Unfortunately, there is no treatment for these vision impairments. Treatment will depend upon cause. Since this condition is a structural defect, a veterinarian will not be able remediate its appearance. Secondary conditions that may occur or run concurrently can be glaucoma or cataracts.  An older dog with sudden vision loss is more likely to experience depression and anxiety than one born with an impairment. The owner must ensure protective precautions at home and in the yard.

Veterinarians often recommend dogs with ocular disease re-learn the environment one or two rooms at a time. Owners must concentrate on locking doors, erecting fences, blocking stairs and padding sharp furniture. In most cases, a dog will learn to find food and navigate the environment. Trying to enervate stress such as loud noises and the sudden appearance of a stranger will make a difference for the pup. Dogs with hereditary vision disease should not be bred.

Dog owners can see their way through ocular disease with the help of their veterinarian. In cases of dogs with significant vision weakness or loss, there will be an adjustment period for all members of the household. Patience will be important. Hopefully, the animal’s resilience, as well as training and human support will allow the dog to enjoy a long, happy life.