All Dogs' Eyes Are the Same Size!

The Seeing Eye breeds all its own dogs, and keeps meticulous record of any genetic defect that could affect a dog's fitness for work, such as hip dysplasia. Although Vinnie was perfectly healthy, his bloodline had been stopped because of a hereditary retinal defect. Since the Seeing Eye had a definite interest in making sure none of their dog graduates went blind, they arranged for Vinnie to be checked, annually, by a veterinary ophthalmologist.



Even in this age of specialization, it's difficult for me to imagine what it is that makes someone get on the path to become a veterinary ophthalmology. Before Vinnie had to be checked, I had no idea such a specialized vet existed, and was apparently busy enough to have a thriving practice in a smallish city such as Albuquerque.

I bring this up because this doctor, whose name I can't recall, told me something I've never been able to forget. He told me all dogs eyes are the same size.

Initially, I didn't understand what he meant, so he explained. "If you scooped out the eyeball of a Great Dane and a Chihuahua," the vet told me, "And laid them out on the table, the eyeballs would be the same size." What can you say when you're given a piece of information like that?

"Oh."

"The eye is the first major organ to develop in a fetus," The doctor explained. "It's a series of genetic switches being pulled, or not being pulled, as the dog develops, that determine what kind of characteristics they have. A small dog, for instance, has genetic switches for growth flipped to the 'off' position, sometime early during gestation. A giant dog, like a Newfoundland, never has those genes flipped off."


"But all the variation you see in dogs, size, color, temperament, all the variation, takes place on the genetic level after the eyeball has developed. That's why small dogs often seem to have bulging eyes. Their skulls are holding the same size orbs as their gigantic brethren."

The vet allowed that there were minute differences in eye size, and that disease, or bad genetics. could result in an eye larger or smaller than usual, but, all things being equal, all dogs have the same size eyeballs. 

I've refrained from scooping any dog's eyes out to compare size, but as I look at dogs I know, I'm fairly confident the vet was right.

I can find no confirmation, or denial, of this "fact" on the internet. I once spoke to another vet, this one a general practitioner, who adamantly denied the assertion. So I don't know, for sure, but, as is my habit, I go around repeating it as fact anyway. After all, a veterinary ophthalmologist told me. Why wouldn't I believe it? You, on the other hand, are being given this information by some lunatic on the internet. Believe it or not, the choice is yours. I'm simply truthfully sharing what I was told.



I'll say this. What the doctor said makes sense. Little dogs do seem to have enormous eyes, while bigger dogs can seem to have a beadier countenance, and I choose to believe what the specialist contracted by the Seeing Eye told me. It squares with my understanding of neology and dog evolution and development. Mainly, though, I choose to believe this because, in any situation, when the room falls silent, and no one knows what to say, this is guaranteed to cause some sort of reaction:

"Hey, did you know that if you scooped out a Great Dane's eyeballs and a Chihuahua's eyeballs, you could put the Dane's eyes back in the Chihuahua, and vice versa, and they'd fit?" 

If that doesn't start the conversation up, it's probably time for everyone to just go home and go to bed.



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