Smart Varifocal Reading Glasses

Ai-Hou Wang

In recent years there appears a kind of multifocal reading glasses sold in the over-the-counter store (see figure).

There is an attached tag saying “Smart varifocal reading glasses, Black technology” (see figure).

Smart varifocal reading glasses is different from conventional progressive multifocal reading glasses. It’s an aspherical lens, of 360° symmetric. Center for near and periphery for middle distance.

Currently the varifocal lens has not been customized for any refraction. Its design is for emmetropic people only. About +2D in the center and +1D in the periphery. Kind of negative aspherical aberration.

Varifocal lens can not achieve 3-diopter range as conventional progressive multifocal reading glasses. It’s kind similar to office lens that extends focus for about 1-diopter (extended focus).

It’s suitable for many circumstances. For example,

In the clinic, you’d be able to both see patient’s eye and key in data on computer.

On desk work, you’d be able to both read paper manuscript and view desktop screen.

During presentation at conference, you’d be able to read documents, read middle-distance computer and see audience in the distance (slightly blurred).

I’ve never read on optics textbook about the application of aspherical lens as multifocal reading glasses. Yet many glasses factory at south-east China had already implemented its production.

I have nevertheless noticed in the store that there are fake monofocal reading glasses with the same attached tag on them.

It’s not difficult to differentiate the aspherical varifocal with the monofocal. Hold the glasses some half meter in front of you. View a straight line through the lens. If it remains straight this is monofocal lens. If it looks curved, as if there’s a convex lens in the center, this is aspherical varifocal lens.

Hope this innovative aspherical varifocal reading glasses could soon be customized to fit people with different refraction. It seems not too difficult technically.