The marketing concept
Poor people often do not have the money to travel to a city in order to buy glasses. Therefore, our opticians come to the people in the villages and provide them with matching glasses on the spot.
In their luggage they have a box with lenses from -6 to +6 diopters and finished curved frames of different sizes. The visual acuity of the patient is determined by a simple eye-chart. When the right lenses are found, they get clicked into the frame. The patient is getting his new pair of glasses immediately.