Hyperchromatic lenses as potential aids for the presbyope.

It has been suggested that a 'hyperchromatic' lens which enhanced the longitudinal chromatic aberration (LCA) of the eye would increase its depth of focus (DOF) and hence might prove a useful aid to presbyopes who have lost their natural ability to accommodate for different distances. Experiments are described in which high- and low-contrast visual acuity, and contrast sensitivity were measured as a function of object vergence using the naked eye and various levels of effective lens-eye LCA. It was found that doubling the effective lens-eye LCA increased total DOF in the high-contrast acuity task by about 0.5 D, while correcting the ocular LCA reduced DOF by about 0.3 D. On the other hand, enhanced LCA led to some loss in performance in the low-contrast acuity task and in contrast sensitivity.