**1. Introduction**

In recent years many mutations in genes that are responsible for several Mendelian eye diseases have been identified and characterized. Genome-wide association studies also advanced our knowledge of complex diseases [1-4]. However, for many diseases, varia‐ tion in phenotype with a single genotype, disease susceptibility among individuals, dis‐ cordance in monozygotic twins, progressive nature of the disorder and age-related onset cannot be explained by accumulating mutations alone [5-6]. Therefore, there must be an‐ other layer of information. This missing link could be epigenetic factors. The term epige‐ netics refers to the mitotically heritable changes in the pattern of gene expression without any changes in the DNA sequence and the term epigenomics denotes the study of epige‐ netics on a genome wide basis. Epigenetics is an emerging field in ophthalmology and is involved in the regulation of gene expression during normal eye development. It has also a role in the etiology and progression of several common human diseases [7]. Epigenetic regulation through environmental factors such as diet, smoking and pollution may result in changes in gene expression that may lead to an increase in disease susceptibility, varia‐ tion in phenotype and progressive nature of many common diseases such as age-related macular degeneration and glaucoma. These epigenetic changes may be age-related and cell or tissue specific. They may also persist throughout the lifetime of an individual. An understanding of the role of epigenetics is important to the success of the stem cell-based therapies [8]. Although epigenetic studies on glaucoma are limited at present [9], in this short article, an attempt has been made to summarize this emerging concept of genetic and epigenetic contribution to the manifestation of glaucoma.

© 2013 Shastry; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2013 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
