What exactly are “dead eyes”?

I don’t think I have the worst level of cognitive empathy ever. Like if you give me a situation, I could tell how you’d probably feel based on it (e.g. if you told me your grandma died, I’d automatically know you’re probably sad).

But when it comes to facial expressions, I just can’t. I can’t decipher what faces mean.

I was watching people discuss psychopathy on YouTube and TikTok, and apparently having “dead eyes” is a major sign. What does that mean?

I searched it up and it literally just says eyes that have no soul or no sparkle. How can eyes not sparkle. It’s an eye. It shines, it’s gonna sparkle. Also “having no soul”? How can you see that in someone’s eyes? How?

Can someone please explain this because I genuinely don’t understand 😭