Risk Factors and Different Types of Glaucoma

The following risk factors have been associated with the development of one or more types of glaucoma:

  • Elevated eye pressure:
    • Eye pressure can vary considerably over 24 hours. So, one eye pressure measurement taken in the office does not provide an accurate assessment of eye pressure as elevated eye pressure may occur intermittently in glaucomatous eyes. However, most eye care professionals define the normal eye pressure range as between 10 and 21mmHg (millimeters of mercury which is a pressure measurement).
  • Age:
    • Over age 60
  • Ethnic Background:
    • People of Black African and/or Black Caribbean descent, Hispanics, and Asians have an increased risk of developing glaucoma, developing it at an earlier age and a more advanced stage than those White individuals.
  • Family History:
    • Family history of glaucoma, such as a sibling or parent with glaucoma. The most common type of glaucoma, primary open angle glaucoma, is more common in people with a family history of glaucoma.
  • Refractive error:
    • High myopia, or nearsightedness, has put patients at a greater risk for the most common type of glaucoma, primary open-angle glaucoma.
    • High hyperopia, or farsightedness, increases the risk for glaucoma related to a blocked drainage system of the eye also called narrow-angle glaucoma or angle closure glaucoma.
  • Corneal thickness:
    • Cornea is the structure in the front of the eye that gives a particular refract. A thin cornea can increase the risk of glaucoma, specifically corneas with a central corneal thickness of less than 0.540 millimeters.
  • Medical conditions:
    • Diabetes mellitus: Patients with uncontrolled diabetic mellitus can result in diabetic retinopathy, which can block the drainage system of the eye and cause a specific kind of glaucoma
    • Injuries or Surgeries: Injuries to the eye, such as blunt trauma and sports injuries, or a history of multiple eye surgeries for chronic eye conditions can cause secondary glaucoma. Blunt trauma can create inflammation in the eye or alter the anatomy of the eye’s drainage system and place the patient at increased risk for the development of glaucoma. Inflammation occurs with any eye surgery but is usually limited and causes very minimal alteration of the anatomy of the eye’s drainage system. Rarely, more inflammation and/or damage to the drainage structures in the eye can occur, putting the person at increased risk for glaucoma.
    • Other conditions: Several conditions may increase the risk of glaucoma, but further research is still needed to stratify this risk: sleep apnea, thyroid disorders, migraine headaches, low blood pressure, and hypertension.

Ways to Reduce Your Risks

  • The best ways to reduce your risk of experiencing permanent vision loss from glaucoma are to get regular comprehensive eye exams and to follow the treatment regimen prescribed by your eye care professional.
  • If you have problems with the eye drops prescribed for your glaucoma, do not stop taking them. Instead, contact your eye doctor immediately to determine if you need to change your medication.
  • The onset of glaucoma usually does not cause noticeable symptoms, so early detection, informed management of your glaucoma, and ongoing follow-up exams are crucial to limiting vision loss.

Resources and Information

Updated by Sefy Paulose, M.D,, March, 2022

Different Types of Glaucoma

Glaucoma is a group of eye diseases that can lead to blindness by damaging the optic nerve. The eye continuously produces a fluid called aqueous humor that must drain through the eye’s drainage system, or angle, to maintain healthy eye pressure. The different types of glaucoma are described by whether this drainage system is open or narrow. One cause of increased eye pressure is when the drainage system, or angle, is narrow or blocked.

Primary Open Angle Glaucoma

The most common type of glaucoma in the United States is Primary Open Angle Glaucoma (POAG). In POAG, the eye’s drainage system appears to be normal or open, yet the eye has high pressure. This is due to the increasing fluid production in the eye or aqueous humor. If the fluid in your eye can’t drain fast enough, it creates pressure that pushes on the optic nerve in the back of your eye.  Over time, the pressure damages the optic nerve, which affects your vision. People often do not have symptoms until they start losing their vision, and they may not notice vision loss immediately. (Types of Glaucoma | National Eye Institute (nih.gov))

Open-angle glaucoma is termed “primary” if no other underlying factors could cause the elevated pressure. If there is an identifiable cause for increased eye pressure, the condition is called Secondary Open Angle Glaucoma (see below).

POAG is treated by decreasing the production or by increasing the drainage of aqueous humor. This can be achieved with medications (eye drops or pills), specific kinds of laser treatments, or by surgery.

Primary Angle Closure Glaucoma

Primary Angle Closure Glaucoma is much less common than POAG in the United States. In this type of glaucoma, the aqueous humor cannot drain properly because the entrance to the drainage canal is either too narrow or closed completely. In this case, eye pressure can occur episodically, mainly when triggered by pupil dilation, which happens intermittently throughout the day with changes in light. If the angle is narrow but not completely closed, symptoms can be vague such as pain, headaches and blurry vision. Symptoms of sudden angle-closure glaucoma can include sudden eye pain, nausea, headaches, and blurred vision. If you experience these symptoms, you should seek immediate medical treatment.

Normal-Tension Glaucoma

In this type of glaucoma, also called low-pressure glaucoma, the eye’s drainage system appears normal, and the eye pressure is not elevated. Yet, there is still evidence of optic nerve damage. This type of glaucoma is treated much like POAG, but the eye pressure needs to be kept even lower to prevent the progression of vision loss.

According to the NEI, “You may be at higher risk for normal-tension glaucoma if you:

  • Are of Japanese ancestry
  • Have a family history of normal-tension glaucoma
  • Have had certain heart problems, like an irregular heartbeat
  • Have low blood pressure”

Secondary Glaucomas

Secondary glaucomas develop as secondary to, or as complications of, other conditions such as eye trauma, cataracts, diabetes, eye surgery, inflammation, or tumors.

Treatment of these would include treating the underlying cause of glaucoma and eye-pressure lowering medication as above. As in the other types of glaucoma, the sooner eye pressure is normalized, the more functional vision can be preserved.

Examples of normal vision, early glaucoma, advanced glaucoma and extreme glaucoma

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