Cats are ambush predators – they lay in wait and pounce so they need to be able to judge distances very precisely to allow them to do that and vertical pupils give them that ability but only if you are close to the ground so larger cats have round pupils. For example foxes also have slits but wolves have round pupils. Round pupils seem to be linked to animals that actively chase down their prey.

Here is an article about it

My cats have round eyes at times of low light.

Cat’s eyes clock

According to Animal Adventures…
Unlike cats with vertical slits, lions have round pupils. No one knows for sure why this is so, but scientists have put forward a persuasive theory to explain the differences in the eyes of both felines. Basically, lion eyes don’t look like cat eyes because they are bigger. They hunt prey differently and are more active during the day than at night. Martin Banks, a professor of optometry at UC Berkeley, conducted extensive research on this subject to answer the question of the difference in eye shape in different animals. The study, carried out in collaboration with Durham University in the United Kingdom and published in the Science Advances journal, presents a hypothesis that links eye shape to the ecological niche occupied by an animal. For the study, Banks and his colleagues analyzed 214 land animals. The scientists correlated these animals’ eye shapes (round, horizontal, and vertical) to their lifestyle in terms of how they forage for food and the time of the day they were more active. Based on this research, the main reason the eyes of lions don’t look like that of small cats is their place in the ecosystem. The researchers discovered that taller animals that chase prey, such as lions, tigers, and wolves, tend to have round pupils. Conversely, The small cats had vertical slit pupils because they were more likely ambush predators. Their small size means they cannot chase prey actively like the big cats. Instead, they hunt by stealth. Hence, BOTH @Lightlyseared & @RayaHope are correct!!!

I love it when a cat’s pupils get huge! You know they’re excited and are watching something intently or are about to pounce on something…sometimes you!

^^ Yes, they are fun to watch even when you’re the one to get attacked!!! I had one male whose pupils grew huge & he twitched all over just before he pounced. I always laughed at him & warned him to never play Poker!!!

@Hawaii_Jake There’s a Netflix documentary that you might like, called “Inside the Mind of a Cat.” It’s all about house cats – how we think of them as being emotionally distant and they’re not, and about how their bodies work to enable them to land upright when they fall, how to read their body language, etc.

@jca2 Thanks