I touched on this problem when I discussed weird-looking dogs some time back. After looking at little Buddy the Boston Terrier today, I feel a need to talk more about it.
Buddy, like most Boston Terriers, is exophthalmic, or "bug-eyed", as I like to say. Boston Terriers are not as extreme in this respect as some other breeds, notably the Pug, Shih T'zu, Lhasa Apso, and Pekingese. All have this in common: they lead with their eyeballs. Look at yourself in the mirror and you will see that your eye sits back behind the ridge of bone where you wear your eyebrows (unless you've got a serious thyroid problem like the late Marty Feldman). This is a good thing. If you do a face-plant on something, your eye will be back out of the way. Not so the little bug-eyed dog. He has a number-8 eye in a number-5 socket. This leads to several problems.
First, since his cornea is so prominent, it is easily injured. Buddy scratched his eye on something unknown yesterday. His owner didn't see him get hurt, but he noticed him squinting a lot and rubbing it last night. Second, if you rub it, you can damage it a lot more. Third, since it sticks out so much, it doesn't get very good tear-film coverage. That's bad, as the cornea derives most of its nutrition and support from that tear film, since it doesn't have any blood vessels (normally, that is). So, you have a structure that is in a vulnerable spot, with poor support for healing. This means that things can go south in a hurry.
A surface scratch on the cornea may heal rapidly on its own, or it may need a little support in the way of infection control with an antibiotic ointment or drops. For superficial scratches or ulcerations, ointments are best, as they stay in the eye for hours, as opposed to drops which wash out in fifteen minutes or so. For deeper defects, the ointment is not a good idea, as the glop forms a barrier that actually interferes with healing. Buddy's cornea has a groove 1/4 inch long, and 1/3 of the depth of his cornea, and this is severe. If it were any worse, we'd be doing a graft of tissue into the wound to support it. For the next twenty-four hours, we will be a little more conservative than that, but we'll be treating aggressively. He will have atropine drops to dilate his pupil, as much of his pain is due to spasms of his iris muscle (like having a cramp inside your eye). Ciprofloxacin drops to kill bacteria will be used four to six times daily, since they won't stay in there long. Rimadyl will be given orally, also to help with his pain so that he is less likely to injure himself by rubbing the eye. We will also use autogenous serum four to six times daily in his eye. Since his cornea has no blood supply, we take a sample of his own blood and use the liquid part (with the blood cells removed) as an eye drop. This puts his body's own healing factors right where we need them without having to wait for his body to grow an abnormal blood vessel over to the wound (which it would do, given enough time -- we just can't wait that long). We'll be following Buddy's progress daily because we don't want him to lose that eye.
Another weird thing that happens with bug-eyed dogs is proptosis globus, meaning that your eyeball is popped out of socket. Any sudden pressure in the head and neck area can do this. In veterinary school they told us you could do it by grabbing the scruff of the neck. I've never seen that, but it doesn't take much. I once had a Shih T'zu patient who popped his eye out while alone in the home for thirty minutes, and I still don't know how he managed that. Of course, head trauma will do it, too, and it is frequent complication in dog fights.
When this happens, the optic nerve and blood vessels are severely stretched. If the eye can be replaced rapidly, vision can sometimes be saved. We hope to at least save the eye for cosmetic purposes, even if vision is lost. This needs treatment as soon as possible, as the stretch on the vessels and nerve rapidly causes permanent damage. The cornea begins to dry out very quickly as well. It should be obvious that this constitutes an emergency requiring treatment as soon as possible.
The thing is, with a bug-eyed dog, any injury to the eye rapidly gets worse and should be considered an emergency. A scratch on his eye is not as dramatic as being popped out of socket, but blind is blind. If you see your pet squinting or rubbing his eye, if you see drainage or the cornea looks cloudy, that is not the time to "wait and see". There are a lot of one-eyed Pekes and Pugs around.
Cats and dogs have a third eyelid. Normally you don't see it, as it stays tucked down in the corner of the eye. There are tear-producing glands on the back side, and periodically it sweeps across the eye like a windshield-wiper, spreading the tears during the blinking process. When the outer lids droop, they close together. When the third eyelid (nictitating membrane) droops, it slides out over the eye. Most of the time, it just indicates that the pet is feeling crummy. If an animal is really feeling low, it may cover most of the eye, which leads to frantic phone calls saying "My dog's eyes have rolled back into his head!!" Of course, that couldn't really happen, as it would rip off your optic nerves when the eyeball rolled around 180 degrees. The pale third eyelid can resemble the white of the eye (sclera) and that's what fakes people out.
