Adjustable Glasses Help the World's Poorest See Better

Some 30,000 pairs of the spectacles have already been distributed in 15 countries, but Professor Silver and his team plan to launch a trial in India, which will, they hope, distribute 1 million pairs of glasses. Their target is to distribute 100 million pairs annually, within a few years. With the global need for basic sight-correction, estimated at more than half the world's population, Professor Silver sees no reason to stop at a billion.

The Adaptive Eyecare (Oxford, UK) spectacles rely on the principle that the more curved a lens is, the more powerful it becomes--an optical function similar to that of the crystalline lens in the human eye. Inside the device's tough plastic outer lenses are two clear circular membrane sacs filled with fluid, each of which is connected to a small syringe attached to either arm of the spectacles. The wearer adjusts a dial on the syringe to add or reduce the amount of fluid in the membrane, thus changing the power of the lens. When the wearer is happy with the strength of each lens the membrane lens is sealed by twisting a small screw, and the ancillary syringes used for lens adjustment are removed. The process takes less than a minute for both eyes. The power range of the lens is +6 to -6 Dioptres, and the optical quality is similar to that of the typical human eye.

The implications of bringing glasses within the reach of poor communities are enormous, said Professor Silver. Literacy rates rise, fishermen are once again able to mend their nets, and women can return to weave cloth. During an early field trial in Ghana (funded by the British government), Professor Silver met a man called Henry Adjei-Mensah, whose sight had deteriorated with age, and who had been forced to retire as a tailor because he could no longer see to thread the needle of his sewing machine.

"So he retires. He was about 35. He could have worked for at least another 20 years,” recounted Professor Silver, who also founded Adaptive Eyecare. "We put these specs on him, and he smiled, and threaded his needle, and sped up with this sewing machine. He can work now. He can see.”

According to the World Health Organization (Geneva, Switzerland) there are currently around one billion people, including 10% of school children, in the world who would benefit from vision correction, but are as yet uncorrected, principally because the numbers of personnel trained to deliver vision correction in the conventional way are inadequate to meet the demand. Around one fifth of any group of people will need vision correction to get the best acuity their eyes can achieve; as a population get older, this fraction also rises, as a condition known as presbyopia--a diminution in the power of accommodation of the crystalline lens--develops. These statistics have profound implications, since hundreds of millions of adults do not have the vision correction they need to be socially and economically active, and many children are educationally and socially disadvantaged.

Related Links:
Oxford University
Adaptive Eyecare
World Health Organization