Negative spherical aberration (SA) is good for reading glasses, but positive SA is not

Ai-Hou Wang, M.D. Ph.D.

For reading glasses, if the 360-degree periphery was made less positive (or more negative) (i.e. negative SA), it will extend the range of vision to middle-distance. It is good

(1) for desktop work – you can read document and at the same time see clearly the desktop computer.

(2) for presentation at conference – on the stage you can read document or computer screen and at the same time see the audience not so blurredly.

Conversely, if the 360-degree periphery of a middle-distance glasses was made more positive (or less negative) (i.e. positive SA) (you may try with Zeiss MyoVision), it won’t help reading documents at near.

This is my observation, but I don’t have satisfactory physiological interpretation for it.

‘Why could our perception utilize negative SA for a range distance of vision while not the positive SA?’

Any optics guru would apply wavefront to answer this question?

Negative SA:

Central part for near (more positive or less negative)

Periphery for distance (less positive or more negative)

Positive SA: (for example, Zeiss MyoVision)

Central part for distance (less positive or more negative)

Periphery for near (more positive or less negative)

(Both negative SA and positive SA are 360-degree symmetrical.)