Genetic Susceptibility to Normal Tension Glaucoma (NTG)

Aims: The Purpose of this short article is to summarize the recent developments in the genetics of normal tension glaucoma (NTG).
Background: Glaucoma is one of the leading causes of irreversible blindness. Primary open-angle glaucoma (POAG) is the most common type of glaucoma in most populations and is frequently associated with elevated intraocular pressure (IOP). However, patients with POAG can also have IOP within the normal range and they are classified as having normal tension glaucoma (NTG) – most likely an independent entity. In NTG, the optic nerve head is just susceptible to normal IOP. Therefore, factors other than elevated IOP are likely to play a role in the pathogenesis of glaucoma. Although factors such as myopia, older age, vasospasm, ischemia and vascular insufficiency are indicated to be associated with the development of NTG, substantial percentage of NTG patients (21%) have a family history of glaucoma suggesting that these patients may have a genetic predisposition for developing NTG.
Methodology: Using the keywords or phrases such as glaucoma, genetics, normal tension glaucoma, open-angle glaucoma and retinal ganglion cell, the literature search was carried out.
Results: NTG is a genetically complex disorder and many genes have been reported to be associated with the development of glaucoma. However, none of them account for a substantial portion of patient population. A complex glaucoma pathogenesis may include interplay among several factors such as genetic, epigenetic and environmental factors. Therefore, an understanding of IOP independent mechanisms of development of NTG is important.
Conclusion: NTG is relatively a less explored avenue of research. There has been paucity of research into the genetic basis of NTG.