Expanding depth of focus by modifying higher-order aberrations induced by an adaptive optics visual simulator

Purpose

To evaluate the impact of higher-order aberrations on depth of focus using an adaptive optics visual simulator.

Setting

Refractive Surgery Department, Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, USA.

Methods

An adaptive optics simulator was used to optically introduce individual aberrations in eyes of subjects with a 6.0 mm pupil under cycloplegia (coma and trefoil, magnitudes ±0.3 μm; spherical aberration, magnitudes ±0.3, ±0.6, ±0.9 μm). A through-focus response curve was assessed by recording the percentage of Sloan letters at a fixed size identified at various target distances. The subject's ocular depth of focus and center of focus were computed as the half-maximum width and the midpoint of the through-focus response curve.

Results

The dominant eyes of 10 subjects were evaluated. The simulation of positive or negative spherical aberration had the effect of enhancing depth of focus and resulted in linearly shifting of the center of focus by 2.6 diopters (D)/μm of error. This increase in depth of focus reached a maximum of approximately 2.0 D with 0.6 μm of spherical aberration and became smaller when the aberration was increased to 0.9 μm. Trefoil and coma appeared to neither shift the center of focus nor significantly modify the depth of focus.

Conclusion

The introduction of both positive and negative spherical aberration using adaptive optics technology significantly shifted and expanded the subject's overall depth of focus; simulating coma or trefoil did not produce such effects.