Hi Jake,
Focusing on the 3rd eye is the portal to higher-self witness consciousness and also brings the 2 hemispheres into balance. I have never seen any reference to focusing only on a physical eye to work on a corresponding hemisphere in yogic teachings. The right brain corresponds to the left side of the body, so it fits that if you are right-brain deficient (overly logical) the left side of the body would be weak also.
John