The gradient index and spherical aberration of the lens of the human eye.

We present equations for analysing the primary spherical aberration of the crystalline lens, both as a whole and of its contributing parts. We apply these equations to two examples of gradient index lenses. The spherical aberration of one lens is well outside that expected for real lenses, but that of the other is within this range. We assess the sensitivity of the aberration to changes in surface shape and gradient index distribution. The process is applicable to other models of the gradient index of the lens.