EyeglassesSnap-insDonatedAdjustableContact lensesLaser surgery

Traditional Eyeglasses

In the developed world, eyeglasses are usually obtained through optometrists' practices, and the correction prescription they determine through subjective refraction is sent to an optical laboratory, where lenses are ground to the correct refractive power and cut to the correct shape to fit into frames.

In many parts of the developing world there are difficulties with this approach; suitably trained professionals are needed to measure the prescription required and optical laboratories are expensive to set up and run. Neither of these are available in anything like the number available to meet the current need. Facilities that do exist are usually located in major cities meaning that the cost of access for many individuals, given the time and travel required, can also be prohibitive. As such although this approach can be effective, it is often beyond the reach of all but the wealthiest.

The challenge is to find an appropriate solution that will scale and perform well for the vast numbers of people lacking vision correction worldwide.

Snap Together Eyeglass Kits

An alternative approach to the provision of traditional-style eyeglasses in the developing world is snap-together lens/frame kits or even complete, ready-made glasses in a range of powers. A selection of lenses in a range of powers is provided which can be fitted on-the-spot into frames which are also provided. Careful selection of the lens powers allows a large . Advantages of this approach in the developing world include a much lower capital cost than the cost incurred by traditional lens grinding and optical labs, and that glasses can be built in the field. It enables low-cost local optometrists to set up, obtaining kit refill supplies when necessary. Vision correction can be provided by local non-governmental organisations (NGOs) as part of a local project at relative ease. However, kits or ready-made glasses only solve one part of the challenge. There still remains the need to determine what prescription an individual requires. As such kits that rely on subjective refraction techniques are still limited by access to trained eyecare professionals, although by enabling on-the-spot correction they may still bring significant improvements in efficiency compared to having to use an optical laboratory. A lack of trained professionals is one of the major bottlenecks. If instead a kit is used with an alternative means of determining what correction is necessary, such as self-refraction, then it might be possible to develop an approach which can be scaled to the numbers required.

Donated/Second-hand Eyeglasses

A commonly seen method of providing vision correction in the developing world is the use of donated, recycled or second-hand eyeglasses, provided by people in the developed world for free. A patient obtains their correction prescription and is then given a choice of glasses which have been donated and approximately match their required correction.

Large programmes of donated glasses already run in the developing world, primarily through the Lions Club International. Although they have been quite successful at getting many eyeglasses onto people's faces, they are ultimately limited to the donation supply and the prevalence of donated prescriptions - for example it will be very difficult to match both sphere and cylinder measurements on one pair of glasses.

Donated eyeglasses are also tied very much to trained optometrists and often emergency aid efforts - they are not an easily scalable or sustainable solution for the developing world.

Adjustable Eyeglasses

Adjustable eyeglasses (also known as adaptive eyewear or adaptive glasses) get around the problem that faces many correction techniques by being a single (or very few) unit(s) that can be changed in the field to produce a range of different prescriptions, without needing additional parts or labour.

Adjustable glasses can be used with all refraction techniques, and are particularly versatile when used with the process of self-refraction, allowing the glasses (adjustable by the patient) to set their own prescription and then keep and use that same pair of glasses with the adjusters either removed or locked. Alternatively, subjective or auto-refraction can be used, with the glasses set to the determined power by an optometrist in the field.

There are a number of different lens technologies available that can be used to make adjustable eyeglasses. The Centre takes a keen interest in this field, and has led the way in research into self-refraction and adjustable glasses generally.
READ ABOUT ADJUSTABLE LENS TECHNOLOGIES →

Previous work has determined the suitability of adjustable glasses and the process of self-refraction for vision correction in the developing world, and research is ongoing in new self-refraction studies, and its applicability to children.

Advantages of adjustable glasses/adaptive eyewear for the developing world include a massive reduction in the need and level of trained optometric personnel, simplification and reduction in cost (due to large scale manufacturing) of products held by local vision clinics and other vision projects, and the ability to have large-scale distribution by people who do not have high-level optometric training.

There are a number of difficulties that need to be overcome however; with current technologies astigmatism cannot be corrected, and indeed it is unclear whether a self-refraction approach would be able to provide this level of correction. Extreme cases of myopia or hyperopia may fall outside the range provided by a 'universal' pair of eyeglasses, and a lack of education may provide difficulties in fitting and explanation of the concept for those unfamiliar with vision correction.

Contact Lenses

Contact lenses are a common form of vision correction in the developed world for certain conditions, used by many millions the world over every day.

Sadly, however, there are a number of drawbacks to the application of contact lenses for use in the developing world:

• Many people do not like or feel comfortable wearing contact lenses
• There are much higher long-term care requirements that include consumable cleaning fluids and regular replacements
• Much greater ophthalmological care is required over the course of use
• High costs and lack of access to facilities for low-cost manufacture
• Contact lenses are not suitable for correcting presbyopia - users will still require reading glasses

Laser Eye Surgery

Laser eye surgery (including laser-assisted in situ keratomileusis (LASIK) surgery and photorefractive keratectomy (PRK) surgery) is an alternative to wearing eyeglasses or contact lenses and provides a permanent one-off treatment for a variety of refractive error conditions, and is increasingly practised in the developed world.

• LASIK surgery involves creating a thin flap on the eye's cornea, then folding it to enable remodelling of the tissue beneath it with a laser. The flap is repositioned and the eye then left to heal.
• PRK also involves reshaping the cornea, but the corneal flap created is removed and discarded, allowing the cells to regenerate after the surgery.

Due to the costs involved, the complexity, requirements for follow-up care and requirements for highly-trained ophthalmologists, laser eye surgery is not practical for mass developing world usage.