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Glaucoma

What is a Glaucoma?


Glaucoma refers to a group of diseases that cause damage to the optic nerve, affecting the transmission of signals from the eye to the brain. Glaucoma usually develops without pain or symptoms and is usually progressive. While glaucoma cannot be prevented, it can be controlled to prevent or slow continued vision loss. At least half the people who have glaucoma don’t know they have it. Left undetected and untreated, glaucoma can lead to permanent vision loss.





Symptoms:


  • Varies depending on type of glaucoma

  • Primary open angle glaucoma often develops slowly and painlessly so there may be no symptoms until damage is severe. As the disease progresses, blind spots can develop in the peripheral (side) vision

  • Acute angle closure glaucoma occurs from a sudden blockage of drainage structures, causing rapid pressure build up, and is accompanied by blurred vision, appearance of colored rings around lights, pain in the eye or forehead, redness, nausea and vomiting


Types of Glaucoma:

Primary Open Angle Glaucoma (POAG)

POAG accounts for approximately 90% of all glaucoma cases. The term “open-angle” means that the angle formed by the eye’s cornea and iris, which is where the drainage channels are, is open and normal. In other words, the angle isn’t too narrow for fluid to drain, yet the fluid isn’t draining efficiently, or the eye is producing too much fluid. The excess fluid increases the pressure in the eye. When the pressure becomes too great, it can damage the optic nerve.

At first, POAG has no symptoms. Vision stays normal, and there is no pain. If glaucoma remains untreated people may first notice that they miss objects to the side and out of the corner of their eye. As the disease progresses people may find that they suddenly have no side vision, or “tunnel vision,” and in its final stages, all vision may be lost.


Normal-Tension or Low-Tension Glaucoma (NTG/ LTG)

In NTG the damage to the optic nerve occurs at eye pressures that would be normal for most people, yet are damaging to a particular individual. Researchers think that in addition to eye pressure, NTG may be related to poor blood flow to the optic nerve or other genetic factors. Normal eye pressure or intra-ocular pressure (IOP) is generally between 12-22 mmHg. IOP over 22 is considered higher than normal, but no one number applies to everyone. Normal IOP for one person could be high for another. What counts is the amount of pressure the optic nerve can take without being damaged.


Acute Angle Closure Glaucoma (ACG)

In ACG the fluid at the front of the eye cannot reach the angle and leave the eye because the angle gets blocked by part of the iris. Drainage can be obstructed because either the iris and the lens stick together or pressure pushes the iris against the cornea. People with this type of glaucoma have a sudden increase in IOP. Symptoms include severe pain and nausea as well as redness of the eye and blurred vision. This is a medical emergency. Immediate treatment is needed to restore flow of fluid. Without treatment, the eye can become blind in as little as 1-2 days.


Secondary glaucomas

These glaucomas develop as a complication of other medical conditions. They can be associated with eye surgery, advanced cataracts, trauma, eye tumors, or eye inflammation. One type, known as pigmentary glaucoma, occurs when pigment from the iris flakes off and blocks the drainage structure. A severe form, called neovascular glaucoma, is linked to diabetes. Also, some patients react to steroid medications which can cause elevated IOP.





Risk Factors:


  • High eye pressure (IOP)

  • Over age 60

  • Family history of glaucoma

  • African, Asian or Latino descent

  • Long term use of steroid medications

  • Severe nearsightedness

  • Previous eye injury or inflammation

  • A thin cornea

  • Diabetes

  • High blood pressure

  • Sleep apnea

  • Migraines

  • Poor blood circulation


Diagnosing Glaucoma:


Most people think that they have glaucoma if the pressure in their eye is increased. This is not always true. High pressure increases the risk of glaucoma, but it may not mean a definite diagnosis. Glaucoma itself is determined by several factors, including damage to the optic nerve and loss of peripheral vision. To detect glaucoma the following tests will aid in making the proper diagnosis:


  • Comprehensive dilated eye exam to obtain a better view of the optic nerve to check for signs of damage.

  • Tonometry – a simple, painless procedure which measures the intra-ocular pressure.



  • Pachymetry – measures the thickness of the cornea

  • Gonioscopy – examines the drainage structure with a special lens to determine if the angle is open or narrow

  • Visual Field – measures peripheral (side) vision. Determines if vision has been affected by glaucoma.




  • Optical Coherence Tomography (OCT) – can provide information about the optic nerve and monitor for nerve fiber layer thickness changes.


Treatment:



Although glaucoma can never be cured, treatment often can control it. This makes early diagnosis and treatment important to protect your sight. The goal is to lower the pressure in the eye to prevent future damage to the optic nerve. Prescription eye drops are the most common first line of treatment. There are several different types. They work either by decreasing the amount of fluid that eye makes or by helping the fluid drain better. It may be necessary to change medications or add another type eye drop over the course of treatment. This may be to reduce side effects or find a more effective treatment, or the medicine may not work as well over time. If eye drops do not lower the pressure enough, there are surgical treatment options as well.

There are two main types of surgical treatments for glaucoma, laser and conventional surgery. Surgeries are done as outpatient procedures. After surgery, eye drops may still be necessary, and surgery may need to be repeated. While surgery can lower eye pressure, it cannot restore lost vision. Laser surgery helps fluid drain out of the eye. Studies show that laser surgery is very good at getting the pressure down, but its effects can wear off over time. Conventional surgery creates a new opening for the fluid to leave the eye. This surgery is often done after medicine and laser surgeries have failed to control the pressure well enough. There are also glaucoma drainage devices now available. These are tiny tubes implanted in the eye which redirect fluid from inside of the eye to an external reservoir.

The most important thing to remember is that glaucoma damage is permanent. It cannot be reversed. But medicine and/or surgery help to stop further damage. NEVER change or stop taking glaucoma medications without discussing with your doctor. If you are about to run out, call for a refill. Treatment is life-long. It is important to take medications are prescribed and to be monitored regularly to ensure they are effective.

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