There are several different types of glaucoma, but they are all characterized by damage to the optic nerve.1 The most common is open-angle glaucoma, which accounts for 90% of all cases of glaucoma and is associated with elevated intraocular pressure (IOP).2
Along with closed-angle glaucoma, this is one of the two main types of glaucoma. The term “open-angle” means the angle where the iris meets the cornea is open and normal. This type of glaucoma is also called primary open-angle glaucoma. In open-angle glaucoma, elevated IOP can result in damage to the optic nerve. However, many patients with open angle glaucoma never experience an increase in IOP, suggesting that blood flow or other genetic factors may be responsible.3,4,5 Open-angle glaucoma develops slowly and is a lifelong condition.6 Although it cannot be cured, early diagnosis can provide an excellent opportunity to help slow further vision loss.7
Narrow-angle glaucoma, which is also called closed-angle glaucoma or angle-closure glaucoma,8 is most common in people of Asian heritage and people who are farsighted.9 With this type of glaucoma, the angle between the iris and the cornea is narrower than normal, making it difficult for the eye’s fluid to drain, and causing increased pressure within the eye.10 Sometimes, this increased pressure occurs in extreme spikes.11
Normal Tension Glaucoma
Also called low-tension or normal-pressure glaucoma, normal-tension glaucoma is characterized by optic nerve damage that appears to be pressure-related even though it is not accompanied by high eye pressure. No one knows why this occurs, but researchers think it may be related to poor blood flow to the optic nerve. Risk factors for normal tension glaucoma include people with a family history of the disease, those of Japanese descent, and those with a history of systemic heart disease.13A,13B
Because normal-tension glaucoma, by definition, is not accompanied by high eye pressure, it must be diagnosed by looking for signs of damage to the optic nerve and by checking for peripheral vision loss. Your doctor can scan your eye with optical coherence tomography (OCT) to evaluate the condition of the optic nerve,14 and perform an ophthalmoscopy, a test that lets the doctor see inside the eye to observe the optic nerve. An optic nerve that’s cupped or not a healthy pink color is a sign of trouble. A visual field test will show the doctor any sight loss that may not be apparent to the patient.15
Because the optic nerves of patients with normal-tension glaucoma can be damaged at relatively low levels of IOP16 the condition is frequently treated the same way as “regular” open-angle glaucoma, by lowering IOP with medications and surgery.17
Childhood glaucoma is usually diagnosed within the first year of life, and is the result of abnormal development of the eye’s drainage system, which causes an increase in eye pressure. Symptoms of childhood glaucoma may include enlarged corneas, cloudy corneas, light sensitivity, poor vision, tearing and blinking.18 It is important to note that many children also fail to have any symptoms of their glaucoma in the early stages.19
Other Types of Glaucoma
Secondary glaucoma, unlike primary glaucoma, is not an original condition but a result of another disease, condition, or event, such as eye injury, eye surgery, advanced diabetes, or advanced cataracts. There are many other causes of secondary glaucoma. A comprehensive eye examination can determine the risks.
Secondary glaucoma can be either open-angle or angle-closure glaucoma, and includes:
- Pigmentary glaucoma is an inherited open-angle glaucoma that tends to affect people with myopia. In the nearsighted eye, the concave shape of the iris creates a wide angle, which causes the pigment of the iris to rub against the lens, break into granules, and clog the drainage canals, causing intraocular pressure (IOP) to rise.20
- Pseudoexfoliative glaucoma is when a dandruff-like substance is deposited on the lens of the eye and clogs the drainage system.
- Traumatic glaucoma is a type of open-angle glaucoma that results from an injury that bruises or penetrates the eye. It can occur right after an injury or much later.
- Neovascular glaucoma, is a type of open-angle glaucoma that most often occurs with diabetes. New blood vessels form on the iris and over the eye’s drainage canals, preventing the fluid from leaving the eye and causing a rise in intraocular pressure (IOP).21
1. American Glaucoma Society. Glaucoma Basics & Frequently Asked Questions. http://www.americanglaucomasociety.net/patients/faqs. Accessed February 21, 2013.
2. Glaucoma Research Foundation. Types of Glaucoma. http://www.glaucoma.org/glaucoma/types-of-glaucoma.php. Accessed February 11, 2013.
3. Hoster, M; Review of Optometry: Why More Blacks Have Glaucoma. 2011. http://www.revoptom.com/content/c/29659/. Accessed March 12, 2013.
4. Flammer J, Orgül S, Costa VP, Orzalesi N, Krieglstein GK, Serra LM, Renard JP, Stefánsson. The impact of ocular blood flow in glaucoma. E. Prog Retin Eye Res. 2002 Jul;21(4):359-93.
5. Glaucoma Research Foundation. Are You at Risk for Glaucoma? http://www.glaucoma.org/glaucoma/are-you-at-risk-for-glaucoma.php. Accessed February 11, 2013.
6. Glaucoma Research Foundation. Types of Glaucoma. http://www.glaucoma.org/glaucoma/types-of-glaucoma.php. Accessed February 11, 2013.
7. Glaucoma Research Foundation. What is Glaucoma? What Can I Do to Prevent Glaucoma? http://www.glaucoma.org/gleams/what-can-i-do-to-prevent-glaucoma.php. Accessed March 12, 2013.
8. Merriam-Webster’s Medical Dictionary. http://www.merriam-webster.com/medical/angle-closure+glaucoma?show=0&t=1360593178. Accessed February 11, 2013.
9. The Glaucoma Foundation. Angle-closure Glaucoma. http://www.glaucomafoundation.org/angle-closure_glaucoma.htm. Accessed February 11, 2013.
10. Glaucoma Research Foundation. Types of Glaucoma. http://www.glaucoma.org/glaucoma/types-of-glaucoma.php. Accessed February 11, 2013.
11. Spikes: Glaucoma Research Foundation. What is Glaucoma? Types of Glaucoma. http://www.glaucoma.org/glaucoma/types-of-glaucoma.php. Accessed March 12, 2013.
12. American Optometric Association. Optometric Clinical Practice Guideline: Care of the Patient with Primary Angle Closure Glaucoma, Reference Guide For Clinicians.http://www.aoa.org/documents/CPG-5.pdf. Accessed February 21, 2013.
13A. Glaucoma Research Foundation. Types of Glaucoma. http://www.glaucoma.org/glaucoma/types-of-glaucoma.php. Accessed February 11, 2013.
13B. The Glaucoma Foundation. Normal Tension Glaucoma. http://www.glaucomafoundation.org/normal_tension_glaucoma.htm. Accessed March 11, 2013.
14. American Academy of Ophthalmology, eyeSmart, What Conditions Can OCT Help to Diagnose? http://www.geteyesmart.org/eyesmart/diseases/what-does-optical-coherence-tomography-help-diagnose.cfm. Accessed March 12, 2013.
15. The Glaucoma Foundation. Normal Tension Glaucoma. http://www.glaucomafoundation.org/normal_tension_glaucoma.htm. Accessed March 11, 2013.
16. Stein JD, Challa P. Diagnosis and Treatment of Normal-Tension Glaucoma. EyeNet Magazine. 2007. http://www.aao.org/publications/eyenet/200702/pearls.cfm. Accessed March 12, 2013.
17. The Glaucoma Foundation. Normal Tension Glaucoma. http://www.glaucomafoundation.org/normal_tension_glaucoma.htm. Accessed March 11, 2013.
18. Glaucoma Research Foundation. Childhood Glaucoma. http://www.glaucoma.org/glaucoma/childhood-glaucoma-1.php. Accessed February 11, 2013.
19. Glaucoma Research Foundation. What is Glaucoma? Symptoms of Childhood Glaucoma. http://www.glaucoma.org/glaucoma/symptoms-of-childhood-glaucoma.php. Accessed March 12, 2013.
20. The Glaucoma Foundation. Pigmentary Glaucoma. http://www.glaucomafoundation.org/pigmentary_glaucoma.htm. Accessed march 11, 2013.
21. Glaucoma Research Foundation. Other Types of Glaucoma http://www.glaucoma.org/glaucoma/other-types-of-glaucoma.php. Accessed February 11, 2013.