Anyone who currently wears glasses or contact lenses will have likely consulted an optometrist to determine their prescription ... that is, if they live in the developed world. In developing nations, many people aren't afforded the opportunity to see a professional in this field. Thankfully there are alternatives, one of which are the self-adjustable glasses from Eyejusters.
The British company is aiming to take low-cost, self-adjustable glasses to developing nations. In order to do so, the team of four have developed an adjustable lens technology called SlideLens. This consists of a pair of lenses which act together to correct an individual's eyesight. By sliding one of the lenses over the other from left to right, the prescription changes until the world comes into focus.
There are two different types of SlideLens - positive power (for long-sightedness) and negative power (for short-sightedness). The range of the positive power lenses is from +4.5 to 0 diopters, while the range of the negative power lenses is from 0 to -5.0 diopters. This covers the majority of common cases. The glasses are priced at US$39.95 for the individual buyer, but the main aim is to distribute these to people in the developing world.
No professionals are required in the process of distribution, with anyone who has received basic training able to get involved. After a simple reading test, the type of glasses required by each individual patient is determined. They then choose which color they want, and can adjust the lenses until they're happy. A repeated reading test ensures an overall improvement in the patient's eyesight. The whole process can be seen in the video embedded at the bottom of the page.
Alternative Solutions
These aren't the first self-adjustable glasses ever conceived, with the Adaptive Eyecare spectacles developed by Professor Joshua Silver already on the market. Previous attempts have used fluid-filled lenses to solve the problem, but I personally feel turning a screw to adjust the prescription is a more elegant solution than spectacles adjusted using syringes and tubes. The Eyejusters also look less cumbersome and more stylish, although they wouldn't be many people's first choice of frames. This is function over form, and they do the job they need to do.Regardless of the method used, this is definitely a problem in need of a solution. There are estimated to be 670 million people around the world living without the glasses they need, with 95 percent of the people in sub-Saharan Africa who need them going without. This is due to there being an average of one optometrist per one million people in that part of the world, compared to one per 10,000 in the United States and Europe ... which is a frankly shocking statistic.
Source: Eyejusters via RedFerret
So, not for everyone. Astigmatism is not too hard to check. A pattern of, uniform width, evenly spaced (all angles between lines the same angle, like every 10 or 15 degrees) lines through a point could be looked at. If all lines are uniformly sharp - then no astigmatism. If corrected for near or far sightedness which these glasses do, and lines along one particular direction are much fuzzier than lines of other directions then you have astigmatism, which varies in severity and direction from person to person.
Great fun to drag the lens in the web page illustration though. http://www.eyejusters.com/lens/
If you are over 40 and don't wear glasses for astigmatism, I think these would be great: http://www.eyejusters.com/readers/ pass cursor over "Where to Buy" may be USA only at this time. Then "click her to buy" - $40. Diopter strengths range from 0 to 4.5x *** Adjustment dials are removable and can be re-attached *** Bah: "Adjustable Readers - Due to the popularity of this item, it is temporarily out of stock. Expected to ship within 6 weeks." Also you can enter email address for updates on "adjustable reader" or "developing world". GREAT WEB PAGE IMO.
Reading glasses are all + numbers. Near-sighted prescriptions are all - numbers.
Personally, I don't see why there aren't booths for emergency specs. Walk in the booth. Dial the lenses until they focus for you, and the 3D printer makes you a set. Pay the cashier.