We present a theoretical study and simulation of an adaptive modal liquid crystal lens (AMLCL) where the magnitude and distribution of the surface resistance in the modal layer can be manipulated via radiation. The modal layer of the presented AMLCL is composed of various semiconductor materials that, consequently, define its surface resistance. To modulate the magnitude and distribution of its surface resistance via radiation, a photoconductive layer can be added to the modal layer. We model an AMLCL with 5-mm aperture and 20-μm thickness theoretically. The results show that the lens reaches its maximum optical power at a surface resistance of 160  MΩ  /  □ and a driving voltage of 6 V for a frequency fixed at 1 kHz, which is in close agreement with a previously reported experiment. The effect of irradiation with a Gaussian beam on the optical power of the AMLCL is analyzed for different beam waists. Results indicate that the optical power of the lens increases by 15% and remains constant until the beam waist of the pump light reaches 70% of the aperture diameter. At the same time, AMLCL aberration is reduced by 10%. The optical power decreases rapidly when the beam waist exceeds 70% of the aperture diameter.