Congenital abnormalities of the eyeball or its surrounding tissue are generally evident shortly after a puppy's birth, but may develop within the first six to eights weeks of life. Most defects are genetically inherited; for example, persistent pupillary membrane (PPM), which occurs when strands of fetal tissue remain on the eye after birth, is more prone in Basenjis, Pembroke and Cardigan Welsh Corgis, chow chows, and mastiffs.
Meanwhile, persistent hyperplastic tunica vasculosa lentis (PHTVL) and persistent hyperplastic primary vitreous (PHPV) is most frequently inherited in Doberman pinschers. Multifocal retinal dysplasia (malformation of the retina) is found in English springer Spaniels; collie eye anomaly in collies, Shetland sheepdogs, and Australian shepherds; retinal dystrophy in Briards, photoreceptor dysplasia (malformation of the cells that perceive light and color) in Collies, Irish Setters, miniature schnauzers, and Norwegian elkhounds.
Ocular abnormalities can also develop spontaneously (e.g., colobomas of ther anterior) or occur in utero. Exposure to toxic compounds, lack of nutrients, and systemic infections and inflammations during pregnancy (such as panleukopenia) are other potential risk factors for ocular abnormalities.
There are a variety of abnormalities that can affect a dog's eye or surrounding tissues. The following are some of the more common issues and their corresponding signs:
In addition, hereditary defects, such as corneal opacities, PPM, cataracts, retinal detachement, and dysplasia, are often associated with the following factors:
You will need to provide as much of your dog's medical history as you have available to you, such as in utero conditions (i.e., whether its mother was ill, her diet, etc.), and the dog's development and environment after birth. After taking a thorough history, your veterinarian will test the health of the eye.
A Schirmer tear test may be used to see if your dog's eyes are producing an adequate amount of tears. If high pressure in the eye (glaucoma) is suspected, a diagnostic tool called a tonometer will be applied to your dog's eye to measure its internal pressure. Abnormalities within the eye, meanwhile, will be examined with an indirect ophthalmoscope and/or a slitlamp biomicroscope.
An ultrasound of the eyes may also reveal problems with the lens of the eyeball, the vitreous humor (the clear fluid which fills the space between the lens and retina), the retina, or other problems that are taking place in the posterior (back) segment of the eye. In the case of iris cysts, ultrasound will help your doctor determine if the mass behind the iris is in fact a cyst or a tumor. Cysts do not always behave uniformly: some grow, while others shrink. In most cases follow-ups to check the progress of the cyst will be the extent of treatment, until further intervention is warranted.
Another useful diagnostic method called angiography can also be used for viewing problems in the posterior of the eye, such as detachment of the retina and abnormal blood vessels in the eye. In this method, a substance that is visible on X-ray (radiopaque) is injected into the area that needs to be visualized, so that the full course of blood vessels can be examined for irregularities.
Treatment will depend on the specific type of eye abnormality that is affecting your dog. Depending on your veterinarian's experience with eye diseases, you may need further treatment with a trained veterinary ophthalmologist. Surgery can repair some congenital birth defects, and medicines can be used to mitigate the effects of some types of defects. Congenital keratoconjunctivitis sicca (KCS), commonly known as dry eye, can often be medically treated with tear substitutes in combination with antibiotics. Other medicines called mydriatics may be used to increase vision when congenital cataracts are present in the center of your dog's eye lenses.
In cases of photoreceptor dysplasia, there is no medical treatment that will delay or prevent its progress, but dogs with this condition generally do not suffer from any other physical abnormality and can learn to manage their environment very well, as long as they are able to depend on their environment being stable and safe.
Congenital KCS requires frequent checkups with a veterinarian to monitor tear production and the status of the external eye structures. Abnormalities such as congenital cataracts, PHTVL, and PHPV require checkups twice yearly to monitor progression.
In addition, since most congenital ocular anomalies are hereditary, you should not breed a dog that has been diagnosed with any of these disorders.
The layer of the eye that is charged with receiving and processing images
Something that appears white or light grey on a radiograph
A professional skilled in the study of the eye
Something that is related to the whole body and not just one particular part or organ
A type of tool used to look inside the eye
A type of instrument that is used to measure intraocular pressure
A type of jelly-like substance that is found inside the vitreous chamber
The term used to refer to the part of the eye containing the iris, the cilia, and the choroid.
A membrane-like covering
Anything having to do with the eye
Any growth or organ on an animal that is not normal
A condition in which growth and development are not up to normal standards
To make something wider
A condition characterized by an abnormally large eye.
The wasting away of certain tissues; a medical condition that occurs when tissues fail to grow.
A condition in which a muscle or body part grows defectively
A disorder that has resulted from intraocular pressure
In veterinary terms, used to refer to the front of the body.
The colored layer around the pupil
Inside the uterus
A bundle of fibers that are used in the process of sending impulses through the body