How to get rounding camera effect similar to P.T.

Hi all!

I’m working on the player camera of a first-person horror game and I’m trying to add a few lingering visual effects.

I’ve noticed that P.T. uses an effect to create a sense of rounding. When you look at the wall in the first picture (close to the lamp further away) you can see the wall doesn’t really bend. When you move closer, as shown in the second picture, the wall next to the lamp appears rounded/bend in a subtle way.

Does anyone of you know how to get a similar effect on my first-person camera?

A huge thank you in advance!