Abstract: Paraxial rays and marginal rays entering the eye do not share a common point of focus in emmetropes, adults usually having a slightly positive spherical aberration. There is provided a method of treatment and prevention of myopia by inducing positive spherical aberration in the myopic eye. The cornea 30 of a myopic eye 31 is fitted with a lens 32 having its outer surface 34 formed having increasing dioptric power away from the axis 35 of the lens and cornea 30. Paraxial light rays 36 entering the central portion 37 of the lens 32 are focused on the retina 40 of the eye 31, producing a clear image of an object. Marginal light rays 41 entering the peripheral portion 42 of the cornea 30 are focused in a plane between the cornea 30 and the retina 40, and produce positive spherical aberration of the image on the latter. This positive spherical aberration produces a physiological effect on the eye which tends to inhibit growth of the eye, thus mitigating the tendency for the myopic eye to grow longer.