Microphthalmia is a disabling genetic condition that occurs when a dog's eyeballs are smaller than normal, severely restricting its vision. With this condition, the internal structures of the eye are abnormal as well, resulting in a prominent third eyelid and small eyes that appear to be recessed into the dog's eye sockets.

Microphthalmia is inherited in many dog breeds through recessive genes. It also can appear in puppies whose mothers received certain types of medication during pregnancy. Owners of affected dogs will notice that their eyeballs appear smaller than normal for the animal's breed, and there may also be noticeable signs of visual impairment. In fact, most dogs with the problem are either born blind, or else eventually become blind or severely visually handicapped.

In many breeds, microphthalmia appears in conjunction with other significant eye problems, including cataracts, problems with the cornea and lens, and a condition known as coloboma, in which the iris of the eye is distorted into a cats-eye shape. In mild cases of microphthalmia, the vision usually isn't affected to any significant degree. In moderate cases the dog's eyeballs will fill about half of the eye socket opening, and about 50 percent of these puppies will be born blind. In severe cases, the puppies will be born blind or the condition will be very evident as soon as the puppy's eyes open.

Some dogs with microphthalmia also have hearing loss, especially in merle breeds with predominantly white coats. (These animals also often have eyes that are different colors.)

Microphthalmia is incurable, and animals with the problem should not be bred. Neither should any parents or siblings of the affected dog, since the trait is carried through recessive genes. However, most complications that develop from the disorder, such as glaucoma, can be treated with standard therapies such as eye drops and surgery.

The condition is inherited in the following breeds: Akitas, American Foxhounds, Australian Kelpies, Australian Shepherds, Beagles, Bedlington Terriers, Borzoi, Cavalier King Charles Cocker Spaniels, Collies, Dachshunds, Dalmatians, Doberman Pinschers, Great Danes, Labrador Retrievers, Miniature Poodles, Miniature Schnauzers, Norwegian Dunkerhunds, Old English Sheepdogs, Pekingese, Poodles, Portuguese Water Dogs, Rottweilers, Saint Bernards, Sealyham Terriers, Shelties, Shetland Sheepdogs, Tibetan Terriers, Toy Poodles and West Highland White Terriers.

Owners of dogs with microphthalmia can help their visually impaired animals in several ways. These include keeping the dog's environment as consistent as possible, introducing any changes into the environment gradually, and developing regular routes for exercise. Be patient with the animal, and the rewards will be worth it.