The eyeball cannot be replaced because it is connected by the optic nerve canal and blood vessels. Although the blood vessels can be replaced and connected, the nerves cannot be connected, and the optic nerve is part of the central nervous system, which is irreversible once damaged, meaning that it is impossible to restore its function. In order to replace the eye, the retina must be replaced and the optic nerve must be connected, which is theoretically unfeasible. This is because once the optic nerve is severed, the sensory function of the entire eye is lost, and even if it is connected to the new eye, no connection can be established with the previous optic nerve, which means that even if the eye is replaced, it cannot be seen. Therefore, both theoretically and practically, replacing the eye is not feasible and is useless.