AdSpecs have flexible lenses filled with a clear fluid. By squeezing the syringe on the side of the glasses, the user shifts the fluid to alter the shape of the lenses and snaps off the syringe to seal the desired prescription into place.
Another U.K. company, Eyejusters, achieve a similar result with a removable magnet attached to the temple of its frame. Like AdSpecs, Eyejusters cost less than $50 a pair. Both are now distributed throughout poorer countries by various charities and foundations.
Frempong says the affordable lenses could be a game changer in places where ophthalmologists are a rarity and affordable corrective lenses are a scarce commodity.
Considering they offer vision correction without the benefit of a professional, Frempong said she thought they would provide adequate eyesight to many people. However, they aren't able to correct more challenging vision problems like stigmatism, she said.
"In poor countries when the choice is between something and nothing, this is certainly a nice something," she said.