For those new to inserting contact lenses, today’s invention is a way to ensure that the lens has been correctly fitted.
The contact lens case would contain a small bulb and battery. This would be held to the wearer’s temple briefly and the bulb lit.
The outer edge of the contact lens on that side then forms a brightly-glowing arc in the visual periphery, indicating not just the presence but also the precise location of the lens. The arc also shows, by its profile, whether the lens is facing inwards or outwards. Future lenses, with circumferential asymmetry, might also indicate their rotational position on the cornea.
Do this in a dark room and an even more prominent after-image of the lens edge forms which can then be used to show up subsequent relative relocations of the lens on the cornea.