blur technique???

if I want to make blur object at max

Do they have to be convex in shapes{
I tried by focusing the eye’s on nose and watching the world

so my shader have to act like this way

or just a blend and sum up with the 4,6 or 8 neighbour texels

I know it look like a stupid Question
but please reply
sorry for my bad english
I hope some one understand what I want to say