Self-Adjusting Lenses to Benefit the World’s Poor

By Paddy Kamen*

It was a simple question, back in 1985, that set Dr. Josh Silver off in a direction that will ultimately give billions of the world’s poorest people improved vision. A friend asked Silver, an atomic physicist and Professor of Physics at the University of Oxford (who is also a vision scientist), if it was possible to make lenses with variable powers. “No," said Silver. But, in the next breath, “Hold on a minute, I can see how to do that.” He immediately sketched a lens and that afternoon went off to his lab and created his first prototype.

Dr. Josh Silver

“The initial lens wasn’t very good,” he allows. They were, however, good enough to inspire him to keep on trying. “The second lens I made that year actually worked very well and when I looked through it I found I could correct my own vision.”

While his research initially had nothing to do with vision per se (he was, among other things experimenting with variable powered mirrors), over time, Silver began to realize that variable power, or adaptive lenses could open the way to inexpensive high quality vision correction to very large under-served populations. “It was my 1996 meeting with the World Health Organization (WHO) on this topic that got me started on the vision angle for the lenses. This was ten years after my initial sketch,” he notes.

Following a period of research and development, Silver distributed 30,000 pairs of these special eyeglasses through a company set up with some friends. He now heads the Centre for Vision in the Developing World (CVDW), a University of Oxford-based organization. The centre works on developing-world vision issues and hopes that one billion people will be wearing the eyeglasses they need by the year 2020.

Silver’s ultra-utilitarian spectacle design relies on the principle that the fatter the lens — and the more curved its surfaces — the more powerful it becomes. The lenses are filled with liquid, and can be adjusted to different strengths by adding or removing fluid from tiny syringes on each arm, then locked to the right strength. Once the fluid is locked in place, the syringes come off and the frames look normal. Explaining the underlying science, Silver says, “When a person adjusts a suitable variable power lens properly, they are in effect linking into their eye-brain adaptive optical system — and actually doing a bit of really quite sophisticated adaptive optics — which can lead them to a best focus condition for their eyes.”

Initially, Silver was working without knowledge of those who had gone before. “Then I started looking into the background literature and found many attempts at making fluid-filled variable powered lenses, the first report of which was from 1747. Another British fellow, Martin Wright, made fluid filled lenses in the 1960’s and 1970’s. He set up a little company, and made 12 pairs for presbyopes. One of his early frames is on display at the British Science Museum, along with one of mine.”

Earlier inventors had not studied the accuracy with which wearers might adjust such lenses. From 1996–2003 Silver and his colleagues did the necessary research and the information is available on his website, at: www.vdw.ox.ac.uk.

“We found that around 80 percent of the population who used the adaptive eyeglasses in the way we told them to would, as a result, be able to pass a driving vision test. The same percentage were able to read quite small print, probably the smallest print they’d ever be likely to encounter,” he explains.

The lenses do not correct for astigmatism, but Silver points out that most people with astigmatism benefit from spherical correction and would thus benefit from the lenses. “Only about ten percent of astigmatics have an astigmatism greater than one diopter, so you’re going to be able to help the majority just by correcting the sphere. It won’t be perfect vision but the person could pass a driving test.”

The need for self-adjusting lenses in an expensive and sturdy frame is enormous. The World Health Organization (WHO) has identified refractive error as the number one cause of low vision in the world today and the second greatest cause of preventable blindness after cataracts. Estimates place the number of people who need vision correction and lack it, at well over one billion. Using the WHO’s recommended measure of a health issue's effect (the Disability Adjusted Life Year), refractive error will rise into the top 10 global health issues affecting productivity and opportunities by 2030, passing HIV/AIDS in its global burden.

Lack of public health infrastructure and a severe shortage of eyecare professionals are major contributing factors to the reality that eyeglasses are unavailable to so many people. While in the UK there is approximately one optometrist for every 8,000 people, in Ghana the number is closer to one per every one million and in Mali the ratio is a stunning one per eight million. A lack of dedicated facilities and equipment also limits access to eyecare. Compounding this issue, the cost of traditional eyewear is prohibitive for the many people surviving on less than a dollar per day.

In much of the developing world, subjective refraction, the process by which optometrists currently assess vision needs in the developed world, is simply out of the question, due to a lack of equipment, facilities, lens materials, laboratories for grinding lenses, and trained doctors. Even hand-held or portable standing auto-refracting devices currently used by opticians in some developing world projects with a high degree of success require expensive capital outlay and training in their usage and still rely on access to traditional eyeglass lenses. Auto-refraction services are also limited in that they can only be delivered on a one-to-one basis. Self-refraction, the process of the wear adjusting his/her own lenses, is an extremely simple and cost-effective alternative that can be deployed with minimal equipment and the mass manufacture of a single identical 'universal' device enables enormous economies of scale, potentially allowing assembly in the nation it is to be deployed in. Further people can be taught in groups to adjust the eyewear to meet their vision needs.

Dr. Silver is aware of research and development going on with other types of self-adjusting lenses and believes that there will be a very significant progress in bringing the cost of such glasses down. Financing is now the issue. “The solution has been scientifically demonstrated to work. And in practical terms, we have placed 30,000 pairs in the field. The challenge is to get the cost of each pair of eyeglasses down to only a few dollars. The project still needs more work and high quality engineering.”

The VDW has partnered with Global Vision 20/20 (www.gv2020.org) an organization with an ambitious and ingenious plan for distributing self-adjusting eyewear. Global Vision 20/20 makes the devices and the training in their deployment available to any qualifying non-profit, NGO, or government organization at no or low cost. This allowing to take advantage of the distribution networks and contacts that these organizations have made throughout the developing world.

Initial research into the ability of young people to use self-adjusting lenses should be completed soon, according to Silver. “We’re currently studying adolescents and hope to study younger children. The work is ongoing and expected to be scaled up. Children’s vision correction is very complex because their accommodation can be very large. Even in the developed world with good access to professionals and all sorts of instrumentation it can still be rather difficult to get an accurate prescription for a child. We’re working very hard to find a strategy for children because hundreds of millions of their lives are blighted by not being able to see properly only for the want of vision correction.”

Donations to VDW and Global Vision 20/20 can be made through their websites.

*With notes from the VDW website, quoted with permission.