Cats and dogs can develop a variety of maladies associated with the eyes and surrounding structures. Below is an overview of some of the issues that can arise in our cats and dogs eyes as well as how we as pet owners can identify if there is a problem.
There are a number of eyelid related health concerns that I see on a regular basis in my patients. Dogs and cats can develop masses that stem from the eyelids, often arising from associated glands. They often start out very small, and go unnoticed until they reach a size in which they can cause a problem. This usually happens when the mass becomes inflamed or grows in a way that allows it to make contact with the cornea. If this happens you will most likely notice your pet develop a runny eye, squinting, or possibly develop conjunctivitis, an inflammation of the inside surface of the eyelid and tissue surrounding the cornea. The white part of the eye, the sclera, will often appear red and occasionally a green to yellow mucoid discharge will develop with a secondary bacterial infection. You may also see irritation of the surface of the cornea as well. White opacities, blood vessels and corneal pigment can be seen as a result.
Entropion, an inward rolling of the eyelid margins, is a disorder that most often has a genetic origin. Chow chows and Shar Peis are two of the dog breeds that I most commonly see with this disorder. The inward rolling of the eyelids allows the eyelashes to make contact with the cornea, repeatedly irritating and contributing to signs listed above as with eyelid masses. This can be very painful. Both of these disorders can be dealt with by performing surgery on the eyelid if they are causing discomfort for your pet.
Other Diseases of the Eye
Keratoconjunctivitis sicca, also known as dry eye, is a disorder of the tear producing apparatus of the eyes. Either the quality or the quantity of the tears can be affected. This is important because the tears not only provide lubrication for the eyelids, but they serve as a mode of nourishment and oxygenation to the surface of the eye. This is especially important for the clear cornea which is devoid of blood vessels. The tears also have antibacterial properties. Signs that your pet may have dry eye include: dry appearance to the surface of the cornea, opacities on the cornea, thick dry mucoid discharge, red inflamed conjunctival tissues, and corneal pigmentation. If left untreated, these processes can lead to blindness. These signs most often affect both eyes and the most common cause is an immune-mediated destruction of the tear producing cells.
Dry eye is most commonly diagnosed by measuring tear production with a Schirmer Tear Test. Treatment is achieved by using local immunosuppressant topical eye ointments, supplementing with artificial tears, and treating secondary bacterial infections with topical antibiotics.
A very common finding in older cats and dogs is that of iris atrophy. This is a gradual degeneration of the iris over time. Symptoms include dull appearance to the color of the iris, change in shape of the pupil, decreased ability of the pupil to dilate and constrict, and the development of holes in the iris. These changes can be rather prominent in some older pets but do not typically cause a significant change in vision.
Iridial tumors can be seen in dogs and cats. These often are initially noted as spots of dark pigment on the iris that then grow out from the plane of the iris. Melanomas are relatively common and can be significant if growing aggressively.
A very common change that pet owners see in their dogs and cats as they age is cloudiness in the lens. This process is a normal aging change called nuclear sclerosis and occurs due to the life-long production of lens cells that never leave the confines of the lens capsule. The repeat production of cells is compacted in the finite space of the lens, leading to an increase in density and opacity of the lens over time. This does not typically affect the vision in our pets.
Conversely, a disease process of the lens that does cause vision problems, that many are familiar with, is the development of cataracts. These can develop congenitally, because of toxins, as a result of electric shock, a sequella of diabetes mellitus, or be age related. Progressive white opacities develop often greatly decreasing vision in the affected eye. So-called hyper mature cataracts have a risk of rupturing that capsule of the lens causing inflammation, or uveitis, within the eye. There are currently no medical treatments for mature cataracts. The treatment of choice is surgery.
If you ever note a sudden murkiness or bleeding within the eye itself, this could be a sign of uveitis, or inflammation within the eye. It is important to have your pet examined immediately if this is noted. This can be a sign of a significant systemic, or body wide, disease.
Glaucoma is an increase in pressure within the eye itself. This can be a very painful issue and can lead to blindness. Red, swollen eye balls are a common sign of glaucoma. Intraocular pressures can be measured by your veterinarian, who will try to determine the cause of this increase pressure.
Vision loss can be an indication of disease of the retina, the visual/light sensing apparatus of the eye. This can be a gradual or sudden issue. Progressive retinal atrophy occurs most commonly in older pets. Vision loss slowly progresses, often initially involving night vision. Pet owners will often note their friend gets lost or disoriented in low light situations. This tends to be a degenerative disease and is unfortunately irreversible.
Sudden vision loss can occur due to detached retina. Causes include trauma, sudden degeneration or high blood pressure. Signs that something has acutely affected the retina include sudden blindness and a dilated, unresponsive pupil. Immediate veterinary assistance is important if these signs are noted.
Trauma to the eye and surrounding tissues can result in a variety of concerns. Lacerated eyelids, scratches or ulcers on the cornea, penetrating wounds to the cornea, proptosed (popped out) eye ball are a few of the emergency situations seen with the eyes. Fast action is important in the stabilization and treatment of these injuries.
The eyes are extremely important sensory organ affecting how we and our pets interact with the world around us. Identifying and treating any problems that arise promptly is important in the preservation of eye health. Always remember if it comes to eye concerns, the sooner the better is the key!!! – Peter Olson, DVM
Peter Olson, DVM, is a 2007 graduate of The Ohio State University School of Veterinary Medicine. He and his wife Beth share their home with two dogs, two cats, four turtles and a Russian Tortoise.