can cats see further up & down or left & right?

My wife and I have had this debate for months. She is in optometry school and I know I shouldn’t debate in her area, but I just can’t concede this one:

Cat’s pupils are usually slit-like, like this - () () - not round like human pupils. So does this mean they can see further up/down or left/right? My wife says up/down since the slits are letting more light in from the vertical field of view, but I say left/right because cats would need to see along a wide field of view when hunting (like lions in the wild on the planes) and up/down wouldn’t be as helpful.

So who is right?

Except for minor effects like diffraction at the edges of the hole, I would say that the shape of the pupil doesn’t matter.

Here’s a similar question I asked from a while back. BTW, not all cats have “slit” contraction.

Cat “family” that is.

The slit aperture doesn’t determine how far a cat can see. It does determine how finely t can resolve alon a given direction. Human pupils shrink down in a circle, so as our pupils close down in bright light we lose some resolution , but equally, in all directions. Cats, with slit pupils, don’t lose any resolution in the vertical direction, but trade this against a considerable loss in the horizontal direction. The bottom line is that they can see fine horizontal items, like threads lying on the ground. Or – maybe more to the point – mouse tails lying horizontally. Theyt lose th ability to resolve fine vertical things, like blades of grass, say. I can see how the ability to see bird tails r mouse tails among blurs of vertical standing grass would help the cat.

2 eyes mounted horizontally, I would have to wag they have a greater horizontal field of vision then vertical.

I think that when it’s important for the cat to see well left to right, up to down, they can see equally well in either plane. Look at fluffy next time sh’e chasing a spider across the floor or mauling your hand… when excited or intent on something their pupils dilate to the point of being pretty well round OO. While licking themselves sprawled out on the couch they have the demon-eye () () thing going.

So it’s sort of like saying that you can’t see as well when your eyes are half closed… but as soon as you hear the burgler taking a crowbar to your back door (or as soon as the cat hears the mouse scurry across in front of him) the eyes open wide and you’re up to 100% visual acuity - so it might not really matter much; when they need to see they can.