June 6, 2010
The veterinary team at Bees Ferry Veterinary Hospital know the general rule of thumb, “eyeballs = emergencies.” This meas that, if anyone calls saying that their pet’s eye is red, swollen, squinting etc…, they are to make an appointment right away. Let’s talk about why that is after we talk a bit about what makes dog and cat eyes different from human eyes.
Just like human eyes, an image passes through the clear cornea, is focused by the lens and then hits the back of the eye, or retina. From there it is sent through the optic nerve to the brain for processing. Both dogs and cats also have a third eyelid. This is the pale pink membrane that you will sometimes see when a dog is just drifting off to sleep or if they have been sedated. Tears are produced by glands in the eyelids and they are drained through ducts in the lower lids.
The fun thing about animal eyes is that they have a reflective tapetum. This is a specialized area of the retina that reflects light. This is what you see when your headlights hit an animal in the dark. The tapetum is brightly colored with greens and blues. If you are in the medical field and have access to an ophthalmoscope, look in your dog’s eyes. This reflective tapetum is gorgeous compared to the human’s comparatively boring retina. It is this tapetum that allows the animals to see so much better in low light and it causes that greenish glow (instead of red in a human) when your headlights or flashbulbs hit the retina.
The most common problem that we see with eyes is conjunctivitis. You know of this as “pink eye” in people. Conjunctivitis is simply “inflammation of the conjunctiva”. The conjunctiva is the pink tissue around your eye. It can be caused by bacterial infections, viral infections, allergies and trauma. It is commonly associated with upper respiratory infections in dogs and cats. This condition is not an emergency, but, to the untrained eye and without proper testing, more dangerous conditions can look just like conjunctivitis.
So, whenever we see a dog with red eye, we need to make sure he doesn’t have anything other than simple conjunctivitis. We do this by checking tear production, staining the eye and checking eye pressures.
We check tear production to be sure the dog or cat does not have dry eye. This is a condition common in certain breeds including most of the bug-eyed breeds and cocker spaniels. For some reason the tear glands in these dogs cease to produce proper tears. These eyes produce a thinck mucus instead. The chronic dryness can result in infections and conjunctivitis as well as scarring of the cornea.
Staining the eye allows us to see if there is a scratch on the surface of the cornea. This is a true emergency. Scratches on the cornea are brutally painful and they can quickly become infected. You never want to use the wait and see approach with these . Antibiotics need to be started immediately and close monitoriong is very important.
Finally, we test the eye for glaucoma by checking eye pressures. Again, glaucoma is a serious emergency. And, guess what, it looks like a “red eye” at the very beginning stages. If pressures are increasing in an eye, immediate intervention with special eye drops and other medications are very important and if these don’t bring the pressures down quickly, then referral to a veterinary ophthmologist right away can make the difference between saving the pet’s vision and losing the eye.
So, don’t mess around with your pet’s red eye! Get him checked out by your veterinarian immediately. If you must flush debris out of the eye, you can use plain contact lens sailine, but nevery use any human eye drops like Visene, as these can make matters worse. And, remember, “eyeballs are emergencies”.