Types of Glaucoma: Open & Closed Angle Glaucoma
in Portland, Maine

By Samuel Solish, M.D.

The Glaucoma Specialists at Eyecare Medical Group in Portland diagnose and treat a number of types of Glaucoma. To get a better understanding of the different types of Glaucoma, it is necessary to learn about how the normal eye functions. In the “normal” eye, there is a continuous production and drainage of clear colorless fluid called “Aqueous Humor”. This production and drainage is balanced so that is an equal amount is produced and drained in order to maintain a “normal’ Intraocular Pressure (IOP).

Aqueous flow eampleAqueous Humor is produced by the Ciliary Body, a structure located just behind Iris, the colored part of the eye that is visible. Normally, the Aqueous Humor is drained through a “filter like” structure called the “Trabecular Meshwork,” which is a tissue meshwork located at the base of the Iris.


In the event that there is either too much Aqueous Humor being produced or too little Aqueous Humor is being drained, there is a rise in pressure inside the eye.  This rise in pressure is considered “abnormal."

There are two main types of Glaucoma: Primary Open Angle Glaucoma (POAG), and Angle Closure Glaucoma. These are characterized by an elevated Intraocular Pressure (IOP), or pressure inside the eye. Sometimes it is possible to have damage to the optic nerve, even with a “normal” Intraocular Pressure. When optic nerve damage has occurred despite a normal IOP, this is called Normal Tension Glaucoma.

Secondary Glaucoma refers to any case in which another disease causes or contributes to increased eye pressure, resulting in optic nerve damage and vision loss. As Primary Open Angle Glaucoma and Angle Closure Glaucoma are the most common, we will concentrate on those types of Glaucoma for our discussion.

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Primary Open Angle Glaucoma
The most common type of Glaucoma is Primary Open Angle Glaucoma (POAG). Patients with Primary Open Angle Glaucoma usually have an increase in Intraocular Pressure (IOP) upon routine measurement, called Tonometry. This increased Intraocular Pressure (IOP) results from either too much Aqueous Humor being produced or too little being drained as discussed earlier. The fluid buildup within the closed space of the inside of the eye causes the pressure to rise. This elevation in pressure (IOP) can cause permanent damage to the optic nerve resulting in vision loss. The optic nerve is the connection between the retina and the brain and is responsible for communicating visual images. Once the optic nerve is damaged, it is not able to carry visual images, resulting in vision loss. This is why it is so important to monitor, detect and control Intraocular Pressure (IOP). If left untreated, an elevated Intraocular Pressure (IOP) may, over time, cause total blindness.

Angle Closure Glaucoma
Angle Closure Angle Closure Glaucoma can be divided in two main types: Primary Angle Closure Glaucoma and Acute Angle Closure Glaucoma. Although Angle Closure Glaucoma is occurs much less frequently than Open Angle Glaucoma, it is important to understand it because it has the ability to produce considerable vision loss in a short period of time. Primary Angle Closure Glaucoma accounts for approximately 10% of all cases of Glaucoma and about 2/3 of these once again produce no early symptoms for patients. Acute Angle Closure Glaucoma is one of the only types of Glaucoma that produce distinct symptoms that include pain, light sensitivity, redness, blurred vision, colored haloes around lights and nausea or vomiting.

Angle Closure Glaucoma is characterized by a blockage or complete closure of the drainage structure of the eye-the Trabecular Meshwork. The Trabecular Meshwork is actually a fine filter. If it is blocked or obstructed by any alteration in the size or shape of the surrounding structures, or by change in the size or shape of the tissue itself, it will cause the Intraocular Pressure to elevate. In instances where the meshwork becomes blocked abruptly, it will cause a sudden rise in the Intraocular Pressure (IOP), resulting in Acute Angle Closure Glaucoma. Angle Closure Glaucoma is characterized by this sudden rise in pressure which can cause pain, redness, blurred vision and if left untreated permanent loss of vision. While there can be a several causes of Angle Closure Glaucoma, it is most often caused by anatomical changes within the internal structures of the eye. Angle Closure Glaucoma is considerably more common in farsighted eyes.  Farsighted eyes tend to be smaller.  As individuals age, the Crystalline lens gets larger and can obstruct fluid flow, which forces the iris against the trabecular meshwork.  The resulting high pressure can damage the optic nerve much like open angle glaucoma.

During your general eye exam if your eye doctor observes or measures a narrowed angle, he or she will perform an additional examination procedure called Gonioscopy. This will allow them to fully visualize the meshwork and the angle in order to carefully assess your predisposition to Angle Closure Glaucoma. Gonioscopy is performed by placing a special contact lens on your eye and then using the slit lamp biomicroscope to examine the meshwork and the angle.

Laser Iridotomy exampleIn the event that you are at risk for Angle Closure Glaucoma or in the event that you have Acute Angle Closure Glaucoma your eye doctor may initially prescribe some medication to begin to lower the pressure and then will most likely recommend performing a type of Laser Eye Surgery in order to produce a small opening or hole in the Iris so that Aqueous Humor can quickly and efficiently drain from the eye.

This procedure, called a “Laser Iridotomy,” is quite successful in reducing the risk of Acute Angle Closure Glaucoma as well as treating Angle Closure Glaucoma. Laser Iridotomy is a type of Laser Eye Surgery that the eye physicians and surgeons and Glaucoma Specialists at Eyecare Medical Group will perform right in the comfort and convenience of our office in Portland.

Glaucoma is a very complex eye disease and not simply an elevated Intraocular Pressure (IOP). Nonetheless, when detected early it can be successfully treated. Eyecare Medical Group eye doctors and our Glaucoma specialists provide the full scope of advanced technology diagnostic testing and treatment, as well as taking the time necessary to give each patient the personal education needed to fully understand their condition and get the best possible outcomes for their patients.

If you or a family member or friend have not had a recent Glaucoma screening or eye exam for Glaucoma, please take a moment to request an appointment by calling Eyecare Medical Group in Portland, Maine
at 888-374-2020.

Eyecare Medical Group can help you better understand the different types of Glaucoma including Primary Open Angle Glaucoma and Angle Closure Glaucoma and provides diagnosis and treatment of Glaucoma in Maine. We are conveniently located for patients from Auburn, Augusta, Bangor, Bath, Berwick, Biddeford, Bridgton, Brunswick, Cape Neddick, Casco Bay, Cumberland Center, Eliot, Freeport, Gardiner, Kennebunk, Kennebunkport, Kittery, Lewiston, Old Orchard Beach, Portland, Sanford, Scarborough, South Portland, Springvale, Topsham, Waterville, Westbrook, Winslow, Wiscasset, Yarmouth, Portland, Skowhegan and York Maine.

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