Glaucoma is a disease of the eyes that can lead to vision loss or blindness due to damage to the optic nerve. In order to understand how glaucoma can occur, we must first understand the anatomy of the eye.

The eye is a very complex and important organ of our body. Each eye produces a fluid known as the aqueous humor that, under normal circumstances, should drain from the eye through canals inside the eye in order to maintain a healthy eye pressure.  If the production of aqueous humor is normal, but the drainage is not in pace with the fluid’s production, the fluid pressure inside the eyes (known as intraocular pressure, or IOP) can increase, leading to some types of glaucoma.

Glaucoma can lead to vision loss or blindness by causing damage to the optic nerve. The optic nerve is the nerve that transmits the visual signals from the eyes to the brain, which is what allows us to see.

There are multiple types of glaucoma, with three of the most common types described below:

Open angle glaucoma:

  • This is the most common form
  • Here, the eye’s drainage canals become blocked, but not completely, hence being called “open angle”
  • IOP increases as the fluid drains too slowly
  • Sometimes patients might have no signs or symptoms but can gradually lose their vision if this type of glaucoma is not treated in time
  • It usually responds well to medication, especially if caught early and treated

Closed angle glaucoma:

  • Also called acute or narrow angle glaucoma
  • Much rarer and the IOP rises very quickly, rather than gradually over time
  • Occurs when the opening of the drainage canal gets covered or completely blocked by the iris, which is in close proximity to the canal opening. The iris will change shape if the pupil (the black part of the eye) responds to changes in the amount of light present by widening or narrowing. If the iris covers the canal due to the pupil’s movement, it will obliterate the drainage angle and cause fluid to build up.
  • Signs and symptoms of closed angle glaucoma occur suddenly and may include headaches, intense eye pain, nausea and vomiting, rainbows or halos around lights at night, and very blurred vision
  • Closed angle glaucoma is a medical emergency and should be treated immediately to prevent permanent vision loss

Normal tension glaucoma:

  • Also known as low-tension or normal-pressure glaucoma because here the IOP is within normal range but the optic nerve is damaged due to some reason other than pressure build up
  • Risk factors include: positive family history, Japanese descent, low blood pressure, being female, and having a history of systemic heart disease, such as irregular heart rhythm
  • The initial signs can be loss of vision starting from the periphery (or side) appearing as if you are looking through a tube. It is often called the “silent thief of sight” since there might be no initial signs and symptoms of glaucoma unless considerable loss of sight is observed

If you observe any of the symptoms described above and are in doubt, consult your doctor to avoid any damage to the optic nerve and your vision.

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