The invention relates to an electrochromic optical lens and a method for the preparation thereof. The lens includes an electrode and a counter-electrode bearing an electrochromic material separated by a solid polymer electrolyte. The method consists of preparing the electrode and the counter-electrode and the assembly thereof by the surfaces thereof bearing the electrochromic material by interleaving an electrolyte membrane between said surfaces. The electrolyte membrane is interleaved in the form of a composition free of volatile liquid solvent, including a precursor of the polymer and a salt, which is liquid or which has a dynamic viscosity [mu] between 100 and 106 Pa.s.