Ko ngā peera porowhita he mea hanga ki te mowhiti o roto me te mowhiti o waho me ngā mata porowhita o waho, o roto hoki. Ko ngā peera pito tokotoko he hononga honohono miihini tino tika, he pane āhua kanohi kei reira te peera porowhita e huihuia ana.
