275 recycled glasses analysed in the study were suitable for use he said. "The relatively small proportion of useable glasses contributed to the high societal cost of delivering recycled glasses, which was found to be US$20.49, close to twice that of supplying ready-made glasses," Dr Wilson added. Co-author of the paper Professor Brien Holden, CEO of the Brien Holden Vision Institute, says that recycled glasses have a feel-good attractiveness to those that hand in their old glasses. "Although well intentioned, recycled glasses will neither suit many of those affected by the most common forms of vision impairment, nor provide a cost-saving solution to the problem," he said. "They are expensive to sort, clean and deliver and, in addition, the power of the lenses in a pair of glasses can differ greatly, meaning that a pair of recycled glasses is rarely the same as another person's prescription," Professor Holden said. "This research is extremely valuable in understanding the most efficient method to utilise the limited funding and resources currently available to address this massive need." Kevin Frick, Professor in Health Policy and Management at the Johns Hopkins Bloomberg School of Public Health and co-author on the paper, commented, "When assessing resource requirements for any type of public health intervention it is always critical to consider all the resources used." "Only a careful and rigorous valuation of the relative costs of recycled glasses will yield the insights from an analysis like this one. While some may try to make a counter argument