Calculation of crystalline lens radii without resort to phakometry.

A computing scheme was developed in 1988 to determine the equivalent powers of the eye and its crystalline lens without resort to phakometry. An adaptation to this scheme is described which allows calculation of the crystalline lens radii using an assumed average value for Q. The values obtained for lens radii using this method compare well with phakometric measurements made on 36 eyes (ocular refraction range -9.37 D to + 3.14 D) which suggests that the variations in Q for a large proportion of the population are small.