Objects are distorted with perspective camera

I’m putting my camera in the center, and when objects go far from it, some kind of ‘skew’ is applied to them.

The object in the corner is 1x1x1, but it looks like 1x1x3. And when the balls reach the edges they look bigger.

Is there a way to fix it?

This is the nature of a perspective camera. You can greatly mitigate the issue by decreasing the field of view on the camera and then moving the camera back to compensate. The narrower the field of the view, the less the distortion.