By placing two variable, liquid, cylindrical lenses with their axes crossed at right angles, a lens has been made which produces the effects characteristic of spherical, cylindrical or toroidal lenses, and in addition has the property of variable focus. The useful range of powers is about seven diopters, and the accuracy in repeating any power is satisfactory. Its application to ocular refraction is discussed.
ROBERT GRAHAM, "A Variable Focus Lens and Its Uses," J. Opt. Soc. Am. 30, 560-563 (1940)