I have never noticed the difference in the pupils of cats till I took the two photos below. Photos were taken about two weeks apart and I put them together in Photoshop. It is the same cat in both photos. What do those eyes mean?

the left picture is taken in brighter light than the right one

Cats have "vertical" pupils. Most mammals have round pupils.

The difference are likely from difference in light.
Cat's pupils will also widen before they pounce.

And also change from a good dose of catnip.

Both photos taken on a cloudy day with the cat facing the same direction.

The pupils of eyes (not just cats, yours too) can change in size (dilation) in response to many stimuli, not just the intensity of ambient light. Strong emotion such as fear, surprise, or anger, predation mode, signals of trust and bonding, can all trigger eyes to widen or narrow.

It's just more obvious with cats since their pupils can close down to thin vertical slits, while other animals like us maintain a round pupil no matter the size.

(And there's reasons for that as well: cats have vertical slits so they can acquire prey way above them even though they are low to the ground. Humans evolved round pupils as they learned to stand upright, thus getting a better overall view of the environment, i.e. the "big picture".)

For the pic on the right:

Link to original video: https://www.youtube.com/watch?v=RZ16H0hsQiQ

More cat eye info:
Cats have a hidden third eyelid called a Nictating Membrane which helps to protect the eye.
If this third eyelid becomes partially closed, its a sign your cat may have a health issue.
Also, if your cats pupils are different in size, go to your Vet ASAP. It could mean a stroke or other emergency.

All I know is our 2 rescue cats don't understand that I can't see in the dark. They have a tendency to lay in the middle of the hall at night and think I can see them. They've trained me to turn a light on.

Good looking kitty.

The first picture is of the cat thinking about food.

The second picture is of the cat thinking you have food.

Light differences are the most likely culprit, but stress and adrenaline play a part too. Ever watch a cats eyes when they're jacked up? Their pupils can almost appear round when they're uber-focused.

Left pic cat is content. Right pic cat is focused on something he might want to kill.

quote:

Originally posted by wingspar:
Both photos taken on a cloudy day with the cat facing the same direction.

Same light conditions to YOUR eyes.

Remember, that little joker can see in the dark. So his ability to detect light changes and adjust are WAY better than yours.

As I mentioned before...light or excitement.

https://www.foundanimals.org/eyes-know-cat-thinking/

quote:

Originally posted by kkina:
... Strong emotion such as fear, surprise, or anger, predation mode, signals of trust and bonding, can all trigger eyes to widen or narrow...

kkina nailed it.



.

Some humans have cat pupils. It's a little odd when you notice it. A mutation of some sort.

Also remember that cats only really see motion, not still shots, so they will move their heads around at time to create motion in their field of view. When hunting they remain still so any motion by the prey stands out. And that's one of the reasons prey becomes motionless when scared.

Look up the acuity of cat senses - vision, hearing, and smell - puts human senses to shame. And a dog's sense of smell puts cats to shame.

quote:

Originally posted by kkina:
<snip>
It's just more obvious with cats since their pupils can close down to thin vertical slits, while other animals like us maintain a round pupil no matter the size.
<snip>

Goats have horizontal pupils:

www.google.com/amp/s/www.zmesc...tangular-pupils/amp/

The left picture the cat is deciding how to kill you. On the right he has decided how to kill you and is now deciding when to act. I wouldn't go to sleep without locking you bedroom door.

quote:

Originally posted by Pipe Smoker:

quote:

Originally posted by kkina:
<snip>
It's just more obvious with cats since their pupils can close down to thin vertical slits, while other animals like us maintain a round pupil no matter the size.
<snip>

Goats have horizontal pupils:

www.google.com/amp/s/www.zmesc...tangular-pupils/amp/

Yep, knew that. Goats have pupils in landscape mode so as to scan for predators in a wide view.

The cat in the photos in my first post comes from a few houses away and it is the only cat in the neighborhood that will not run from me. Won’t let me get close unless I have food in my hand and I have been giving him snacks. I only have a few photos of him, so the difference in his eyes was noticeable right away when I saw the photos.

I recently lost my cat just one month short of his 15th birthday and I have over 2700 photos of him, not counting the photos with other cats that he was friends with and I went thru a lot of them yesterday and had trouble finding photos of his eyes when they were not slits. He was a sweetheart of a cat with a temperament and personality that is hard to come by in a cat, which was the only reason I ended up adopting him from my neighbor when he was just shy of his second birthday. He slept on my bed with me and the bedroom is still empty. In all those years, I never noticed his eyes going from slits to round. Now I wish he was still alive so I could study his eyes, something I never did.

I did Google this subject, but I thought it could be a good discussion here.