Question

why ray passes through the optic centre without deviayed

Answer 1

Actually the same happens when theray passes through optical centre. This can be observed in a thick lens. In thin lenses the perpendicular distance between extended incident ray and extended emergent ray is negligible. So we can say that light ray passes through optical centre without deviation.
Hope its help you

Answer 2

because at optic center the angle between ray and surface is 90°