if(Input.GetMouseButtonDown(0)) {

    hit = Physics2D.Raycast(Camera.main.ScreenToWorldPoint(Input.mousePosition), Vector2.zero);

    if(hit) {

        if(transform.name == hit.transform.gameObject.name) {

            Debug.Log("Button touched");
        }
    }
}else
if(Input.GetMouseButtonUp(0)) {

    //hit = Physics2D.Raycast(Camera.main.ScreenToWorldPoint(Input.mousePosition), Vector2.zero);

    if(hit)    {

        if(transform.name == hit.transform.gameObject.name) {

            Debug.Log ("touched up over same button.");
        }else {
            Debug.Log ("touched up not over same button.");
        }
    }
}