Impacts of Spherical Aberration and Coma on Through-Focus Visual Performance
Purpose
To investigate relative contribution of Zernike spherical aberration (SA) and coma to through-focus visual performance (TVP).
Methods
A theoretical simulation was conducted using area under the modulation transfer function curve as a retinal image quality (RIQ) metric. Through-focus RIQ was obtained with various combinations of Zernike primary SA and coma of different signs and magnitudes. The peak of through-focus RIQ was shifted to distance (0D defocus) and the area under RIQ (aRIQ) between 0 and 3.0D was calculated.
Results
In a simulation with exclusively SA, the best average RIQ was obtained when SA was positive. Magnitude of aRIQ was able to be enhanced by 10~18% compared to zero SA. When pupil size was larger than 4 mm, coma didn’t enhance aRIQ. When pupil was smaller, coma could enhance aRIQ, but the enhanced amount was only about 1% compared to zero coma. When combining SA and coma, overall trends of aRIQ followed that of SA’s.
Conclusion
Positive SA enhances TVP when distance image quality was optimized. Among SA and coma, SA has dominant effects on TVP theoretically. However, there might be some discrepancy between this optical simulation and clinical findings, which suggested existence of other factors than optics in visual performance.