How to Detect a gameObject when Clicked near it?

I am working on Angry bird type game.I need the ball to be detected when the user clicks near the ball but i couldn’t. I have tried

OnMouseDown()
function but it detects only when it is on the gameobject.

Not for a GO but works with Colliders

Pick one:
https://www.google.co.uk/search?q=unity+physics2d+overlap&ie=utf-8&oe=utf-8&client=firefox-b&gfe_rd=cr&dcr=0&ei=IUGkWsX3B5GzgAaIyoaIBg

The best Answer I got is to use

Input.GetTouch

If anyone faces similar problem like me click examples from the documentation Unity - Scripting API: Input.GetTouch