A model that considers a photoinduced lens with a focal length dependent on a real power of the incident beam radius is compared with other reported models employed to describe the z-scan curves for thick media. It is demonstrated that this model is equivalent to that used to describe z-scan curves for thin nonlocal nonlinear media; then an extension is made for thick nonlocal nonlinear media. A comparison is made with other models to obtain z-scan curves for thick media. It is demonstrated that, under the same conditions, remarkable differences can be found in the simulated z-scan curves.