The Sommerfeld theory with the Uehling potential

The Uehling potential is the one-loop radiative correction to the photon propagator. The correction can be graphically represented by the Feynman diagram of the second order. The physical meaning of this diagram is the process Y-> (e- + e+) -> Y , where Y is denotation for photon, and e-, e+ is the electron-positron pair. It means that photon can exist in the intermediate state with e+, e- being virtual particles. Then, the Coulomb potential with radiative corrections can be inserted in the Sommerfeld quantum equation in order to find the Sommerfeld energy.