Como Perseu se defendeu de Medusa?

according to french psychoanalysis, specially with lacan, the concept of lack turned to be an important formulation. but what is the concept of lack? what happens when the non-specularizable is not excluded and therefore turns into something specular? when perseus runs into medusa, guided by a bronze shield held by atena, how did this hero defend himself from medusa? what did he do in order to defend himself from the presence of the object that introduces the dimension of the real?