How often do we read “Glaucoma is the second leading cause of vision loss in the world” in the opening sentence of a paper on glaucoma? This is often followed by a reference to Quigley’s report entitled “Number of people with glaucoma worldwide” published in 1996.¹ This seminal report examined all published reports of the prevalence of glaucoma in populations worldwide and estimated that 66.8 million people would have primary glaucoma by the year 2000, with 6.7 million suffering from bilateral blindness. These figures exceeded those predicted by previous surveys which had based glaucoma prevalence on the later stages of the disease when visual acuity is affected.²

The report by Quigley and Broman in this issue of the BJO (p 262) is an important and timely addition to our knowledge in this area. They have estimated the worldwide prevalence of glaucoma for 2010 and 2020. Since Quigley’s original report there have been many more population based surveys of glaucoma conducted, particularly among Asian, Indian and African derived groups where data were sparse until 1995. This is illustrated by their finding that 23 studies published after 1995 satisfied their criteria for inclusion in their model, whereas only 11 studies could be included from all publications up to this date. Population based surveys were chosen to reduce selection bias. One of the greatest problems encountered when comparing the prevalence of glaucoma in different populations is the definition used for glaucoma. This was neatly summarised by Wolfs and colleagues,³ who reported that their prevalence figures (for the Rotterdam Study) could …