Heat 1-inch of oil in a large skillet over medium heat. While oil is heating, combine tuna, beaten egg, green onions, mayonnaise, 1/4 cup bread crumbs, and lemon juice, to taste, if desired. Form into patties and dust with additional bread crumbs. When oil is hot, fry patties until golden brown, about 2 minutes on each side. Remove from oil and drain on paper towels before serving.