Abstract: Glaucoma is the leading cause of irreversible blindness worldwide, which leads to a progressive loss of vision. Glaucoma can be classified into two types: primary open-angle glaucoma and primary closed-angle glaucoma. Primary open-angle glaucoma can be caused by the blockage of the trabecular meshwork, and this results in elevation of the intraocular pressure (IOP), leading to retinal ganglion cell (RGC) death. However, many glaucoma patients have normal IOP; this is known as normal-tension glaucoma. Nevertheless, excitotoxic damage and oxidative stress can also lead to RGC damage in normal-tension glaucoma (Almasieh et al., 2012). Glaucomatous genes such as TIGR, OPTN, and CYP1B1 have been suggested to contribute to the pathogenesis of glaucoma. However, some glaucomatous patients may remain asymptomatic in the early, moderate, and late stages. Another type of glaucoma is primary closed-angle glaucoma. In this clinical condition, a relative pupillary block is contributed by the iris obstructing aqueous outflow. The patients may suffer from corneal swelling, headache, nausea, and blurred vision during the acute phase.