Glaucoma refers to a group of optic neuropathies that cause progressive damage to retinal ganglion cells. This damage leads to cupping of the optic nerve and ultimate visual loss.
Glaucoma is a leading cause of irreversible blindness worldwide; however, the pathophysiology of glaucoma is poorly understood and the exact factors leading to its progression are unclear. An estimated 79.6 million persons are expected to have glaucoma worldwide by 2020.
Glaucoma. Illustration showing open-angle glaucoma. Intraocular pressure in the back of the eye. Image Credit: Sakurra / Shutterstock
What are the Types of Glaucoma?
Glaucoma actually refers to a group of disorders.
Open-angle glaucoma and angle-closure glaucoma are the two major types of glaucoma. Both the types are characterized by an increase in intraocular pressure (IOP), or pressure inside the eye.
What is the Most Common Form of Glaucoma?
Open-angle glaucoma, the most common form of glaucoma, is caused by blockage of the trabecular meshwork or drainage canals. The “open-angle” designation refers to the preservation of a wide and open angle between the iris and cornea. The condition develops slowly over a lifetime, and symptoms are gradual and often go unnoticed.
Open-angle glaucoma is characterized by an imbalance in the production and drainage of aqueous humor (eye fluid). Blockage of drainage canals causes fluid accumulation in the eye chamber, which in turn causes increased IOP. Vision loss from this type is first evident peripherally, then moves centrally.
Angle-closure glaucoma is also referred to as acute or narrow-angle glaucoma. As evident by its name, angle-closure glaucoma results from the narrowing of the angle between the iris and cornea. The condition is characterized by blocked drainage canals, which results in a sudden rise in the IOP.
In contrast to open-angle glaucoma, this type develops quickly and has very noticeable symptoms. The severe nature of the condition warrants immediate medical attention and prompt treatment.
Open-angle and angle-closure glaucoma can also include variants such as secondary glaucoma, pigmentary glaucoma, and traumatic glaucoma.
Normal-Tension Glaucoma (NTG) is also called normal-pressure or low-tension glaucoma. It is characterized by optic nerve damage even in the absence of high IOP. The exact mechanism that causes this damage is still a mystery.
Congenital glaucoma is a rare inherited condition that develops due to the incomplete or faulty development of the drainage canals of the eye. It encompasses a heterogeneous group of diseases and is further classified into the following:
- Congenital glaucoma - The condition exists at birth
- Infantile glaucoma - Identified during early childhood, normally before the age of three
- Juvenile glaucoma - Occurs in later childhood; from age three to the teenage years
Microsurgery is the main treatment option, however, in complicated cases, a combination of medication and surgery is generally recommended.