scope.onFocus = function(){ // change scope variables
};

elem.bind('focus', function(){
   scope.$apply('onFocus()')});

element.bind('focus', function(){
    scope.onFocus();
    scope.$apply(); // don't wrap onFocus call in $apply
})

myapp.directive('onfocus', function() {
      return {
        restrict: 'A',
        scope: {
         onfocus:'=onfocus'
            },
        link:function (scope, element, iAttrs, controller){
            element.bind('focus', function(event) {
                  scope.onfocus();
              });
        }

            };

    });

<input type="text" onfocus="onFocus()" />

scope.onFocus = function(){ // change scope variables
};