A British company says its new adjustable eyeglasses will enable wearers to adjust their own lens prescriptions by turning a knob until they can see clearly. The Eyejusters are made for people who need different prescriptions for different tasks such as reading and watching TV, its developers said, and can be used by people in developing countries who don\'t have access to optometrists. Minimally trained volunteers in such regions would be able to give out glasses that users tweak to their own prescription, they told InnovationNewsDaily. Though wearing incorrect prescriptions can worsen eyesight, they acknowledge, British studies have shown people over the age of 12 can safely use adjustable lenses. Eyejusters lenses consist of two plastic lenses stacked in front of one another, with an adjusting knob that slides one of the lenses side to side, with the two lenses creating different shapes that correspond to a range of prescriptions. In a pilot project, the company has already provided 800 pairs of Eyejusters to people living in rural Morocco.