The obstacles to providing glasses to two billion people who need them: say ‘AAAAA’!
All of the following are required for a person to get the glasses they need: on the demand side, awareness of the need for glasses, the acceptability of wearing them, and their affordability; on the supply side, access to the product and the means to ensure the accuracy of correction. The failure of any one of these aspects will prevent people from getting the glasses they need.
Someone with refractive error needs the basic awareness that the blurriness of distant objects is not “normal” and that it can probably be corrected with a pair of glasses. Older people who have become presbyopic at least know that they once were able to focus on near objects but now struggle to do so; rather than resigning themselves to this “natural” age-related disability, they need to be aware that with a pair of glasses they could continue to focus up close.
A child or adult who has never seen a pair of spectacles or appreciated their purpose will be reliant on someone else in the community being aware of the possibility of blurry vision and how to recognise the symptoms in others. Without some form of simple visual acuity screening, the symptoms of myopia (shortsightedness/nearsightedness) may be misinterpreted: a child may wrongly be judged as less mentally capable in class rather than as simply unable to see clearly what is on the blackboard.
Given the awareness of the possibility of correcting refractive error with a pair of glasses, there needs to be a willingness to contemplate actually wearing them. All cultures have strong norms with respect to personal appearance and especially any decorative or functional modification of the face (make-up; jewellery and other worn objects; veils and other clothing). An unworn pair of glasses serves little purpose. I freely admit my own initial reluctance to wear glasses as a teenage student: I would wear them only in class and only while I absolutely had to read something on the blackboard; at all other times, they sat on my desk. In some cultures, wearing glasses may bring negative associations beyond the aesthetic, from concern over functional disability to superstitious beliefs.
Recognising the influence of vanity and cultural norms, the acceptability of wearing glasses may be one of the harder obstacles to overcome – and one that may have to be overcome in each culture and community in its own way, precluding any universal approach.
If not donated, glasses need to be affordable for the wearer (or in the case of a child, his or her parents). Given the scale of the problem, aid-funded delivery glasses to everyone who needs them is financially unsustainable. Rather, donors must focus on the highest priority groups such as school-aged children. Developing world governments have competing priorities for their health and education budgets and it may be unrealistic to expect them to cover the cost of providing glasses to the whole population in need. A financially scalable approach is a market-based one: people in need buying glasses at a price they can afford.
Given awareness of the need for glasses and acceptance of actually having to wear them, and assuming their affordability, the population in need must have access to the product. The challenge is that a conventional pair of glasses is not just a uniform product but rather the end result of a service involving the creation of lenses of the specific powers required by a particular wearer. In the developed world, this service depends on a highly trained (and well equipped) eye care professional to determine a person’s prescription (i.e. the power of lens they require in each eye) and the optical industry infrastructure to deliver a bespoke product in accordance with that prescription.
So there is a professional problem and a logistical problem in providing access to glasses. I will say more about the professional problem under Accuracy below. But assuming for a moment that the professional problem has been solved – say we have a magic device to find a person’s prescription – the logistical problem still has to be addressed.
The manufacture of spectacle lenses tends to require high precision to achieve optical surfaces of a quality that avoids visible distortions. As I have discussed previously, while a presbyope (i.e. someone who needs reading glasses) can be offered a choice of just two or three convex (positive) powers of lens and typically get a good result, someone who needs concave lenses to be able to see clearly in the distance will need the correct power from a large range of possible negative lens powers. Having selected the correct power of lens for each eye, the lenses must then be fitted into a spectacle frame. Conventionally, where an optician’s shop offers a wide range of frame shapes, the edges of the lenses will have to be cut to fit the frame. Even where lenses are pre-cut to fit a standard frame, someone needs to select the correct lens powers from among the tens or hundreds of possible powers and to assemble them together with frame.
This imposes logistical constraints on the location of manufacture of conventional spectacles: there needs to be the space to store an inventory of tens or hundreds of different powers of lens (i.e different stock-keeping units, or “SKUs”); there needs to be a system to monitor this inventory and order replacements when a given SKU is running low, and people trained to manage this system; there needs to be the transportation infrastructure to resupply within a reasonable time. It can be difficult to support such a complex supply chain in many parts of the developing world, especially as one gets farther from major cities.
The natural response to a fragile supply chain is to hold more inventory closer to the customer. However, this leads to a financial problem: the capital expenditure required to stock a local distributor of conventional glasses (and to provide the necessary training to manage that inventory as well as all other aspects of delivering glasses) has to be spread over the base of customers served by that distributor; but by definition, getting closer to the population in need – especially in smaller towns and rural areas – means a smaller customer base, driving up the unit cost of delivering the product and reducing affordability.
The professional problem is the lack of eye care professionals to serve developing world populations. Some sub-Saharan African countries have ratios of one optometrist per million or more of the population; even if everyone formed an orderly queue and the optometrist worked all day every day, it would take decades to find all the prescriptions (and of course prescriptions can change every year or so, especially in children and young adults).
Even where developing world populations are served by eye care professionals, lower professional standards or weaker regulation can mean that the quality of service is less than satisfactory. As part of our clinical trial of the efficacy of self-refraction by myopic teenagers in rural China1, we also measured the accuracy of the conventional glasses they were already wearing: only 30% of the children were able to see with an acuity of 6/7.5 using their own glasses; in comparison, 97% of them were able to see as clearly after self-refracting using our adaptive spectacles. So while this population was aware of the need and had access to affordable glasses, the accuracy of the delivered product was poor.
The relative accuracy of self-refraction using adaptive spectacles shows the strength of this alternative approach. Teachers were able to supervise the process of self-refraction by their students after just one hour’s training by non-professional. A train-the-trainer approach based on self-refraction addresses the professional problem. But the self-refraction approach also simplifies access: logistically, it is far easier to deliver a single SKU product than to manage a supply chain with tens or hundreds of SKUs. Self-refraction using affordable, aesthetically appealing adaptive spectacles thus addresses obstacles on both the demand side and the supply side.
This is the fourth in a series of articles by Chris Wray on the problem of lack of access to glasses in the developing world.
1. See the paper published in the British Medical Journal in 2011 by Zhang et al., available on our research page.