I had tried something similar on my custom table. but it is not letting the user view fields when they want to create a new record as in the new form loads up blank. I am not sure why its removing field viewing access for new records.

answer=(function(){

if(current.getValue("sys_created_by")== gs.getUserName() || current.getValue("sys_updated_by")==gs.getUserName()){

return true;

}

return false;

})();