Correlated or not: Glaucoma prevalence and modern industrialization

Summary

The higher prevalence of primary angle-closure glaucoma (PACG) among Eskimos, Chinese and Mongolians has long been acknowledged, while primary open-angle glaucoma (POAG) is common in blacks and Caucasians. However, in recent years, the incidence of Chinese POAG has increased to a level similar to that of Western countries, and the urban prevalence is higher than the rural one. Is this a coincidental result, or is it a consequence of modern industrialization? The etiology of glaucoma is believed to be due to both genetic and environmental factors. Genetics plays an important role in the growth of the eye, as demonstrated in ethnic variations in glaucoma prevalence and family studies. At the same time, changes in environmental factors have resulted in countries experiencing one of the most rapid epidemiological transitions in history. For the modern human eye to adapt to a more close-up working environment, and with more education requiring close reading, there have been some changes in the eye structure, including a deepening of the anterior chamber, an increase in myopia, a decrease of hyperopia, etc. The changes in these factors were closely associated with the pathogenesis of glaucoma. And of these factors, myopia may have been the most important contributor. Myopia, as an independent risk factor, may increase susceptibility to glaucomatous damage of the optic nerve in myopic eyes. Myopic eyes are more sensitive to intraocular pressure (IOP) (even normal IOP)-induced stress for the thinner lamina cribrosa and larger scleral canal than emmetropic eyes. Axial myopia has longer axial length of the eye and deeper anterior chamber than the normal eye, leading to a less chance to develop angle-closure glaucoma. Due to the increase in myopia among the younger generation in the process of industrialization and urbanization, we hypothesize that the prevalence of glaucoma is correlated with these changes, and that POAG could become more common in Eskimos, Chinese and other Asian descendants in the future.

Introduction

Glaucoma is a progressive optic neuropathy characterized by optic nerve damage and visual field loss. It is the second leading cause of blindness worldwide, largely due to POAG [1], [2]. It is estimated that there will be 60.5 million people globally with glaucoma in 2010, increasing to 79.6 million by 2020.

As a progressive optic neuropathy, the etiology of glaucoma is still not well understood. It has been suggested that this condition may result from the interaction among several environmental and genetic factors [3]. Genetics plays an important role in the growth of the eye, as demonstrated in various racial and family studies [4]. For example, a shallow anterior chamber was indicated as an inherited characteristic of Eskimos, which could explain the high prevalence of PACG among Eskimos, Chinese and Mongolians [5], [6], [7], [8], [9], [10]. On the other hand, among the black American population, POAG leads as the main cause of blindness [11], [12]. However, the situation seems to have changed in recent years due to the industrialization and urbanization in developing areas. The following epidemic investigation may explain such consequences as the changes in prevalence of POAG and PACG.