Penalization includes all those methods apart from total occlusion which disturb the central vision of one eye by favouring the other eye. Penalization has a sensory action on functional amblyopia; moreover it also has a motor action, influencing the non-accommodative element of spasm in esotropia. Optical penalization is the most classical method. However, one should also be aware of penalization with partial occlusion or fogging, penalization with mydriatics, and penalization with sectors, which are very often used in association with the classical technique.