Computational aspects of the visual Strehl ratio

Abstract

Purpose. The recently defined visual Strehl ratio that is based on the optical transfer function (VSOTF) has a number of previously unidentified limitations in its calculation that need to be addressed.
Method. The VSOTF is complex, not bounded between zero and one, and can be negative. It is also very sensitive to the presence of prisms in the wavefront aberration. Current reports using the visual Strehl ratio for objectively assessing visual performance use its real part in the analyses. This leads to a metric that differs from the visual Strehl ratio based on the modulation transfer function (VSMTF), even in the case of rotationally symmetric aberrations.
Results. An augmented visual Strehl ratio is proposed that overcomes the limitations of its predecessor.
Conclusions. The augmented metric is more robust in the presence of a residual prism than the VSOTF, and it shows in a preliminary study that it could lead to better correlations with visual performance, especially in the presence of larger aberrations.