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Types of Glaucoma

Types of Glaucoma
Two of the more common types of glaucoma that we encounter at Baltimore Washington Eye Center are Primary Open Angle Glaucoma (POAG) and Angle Closure Glaucoma. A less frequent, but noteworthy type of glaucoma occurs when there is a “normal” intraocular pressure (IOP) and yet there is damage to the optic nerve. When optic nerve damage has occurred despite a normal IOP, this is called Normal Tension Glaucoma. Secondary Glaucoma refers to any instance in which another disease causes or contributes to increased eye pressure, resulting in optic nerve damage and vision loss. As they are the more common, we will limit our discussion to Primary Open Angle Glaucoma and Angle Closure Glaucoma.

Primary Open Angle Glaucoma
Primary Open Angle Glaucoma (POAG) is the most common type of glaucoma. In the “normal” eye, there is a continuous production and drainage of a clear, colorless fluid called “Aqueous Humor”. This production and drainage is balanced so that an equal amount is produced and drained in order to maintain an equilibrium resulting in a “normal’ Intraocular Pressure (IOP). Patients with Primary Open Angle Glaucoma usually have an increase in Intraocular Pressure (IOP) determined by a routine test, called Tonometry.

Primary Open Angle Glaucoma is secondary to a decrease in the ability of the eye to drain the aqueous fluid. Any elevation of Intraocular Pressure (IOP) is considered “abnormal. This elevation in pressure (IOP) causes the circulation in the optic nerve to become compromised, depriving it of oxygen and nutrients, resulting in permanent changes and even damage to the optic nerve. Any damage to the optic nerve can result in a loss of vision. When 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 slow, progressive and permanent damage to the optic nerve that can result in 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 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. 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 caused by a blockage or complete closure of the drainage structure of the eye called the Trabecular Meshwork. The Trabecular Meshwork is actually a fine filter, and 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.

Acute Angle Closure Glaucoma is characterized by this sudden rise in pressure which will cause pain, redness, light sensitivity, colored haloes around lights, nausea or vomiting, and blurred vision, and if left untreated permanent loss of vision.

Acute Angle Closure Glaucoma is considered a medical emergency. If you experience a sudden onset of pain, redness, blurred vision, light sensitivity, haloes around lights, or nausea and vomiting, please call Baltimore Washington Eye Center at 800-495-3937  and relay these symptoms to the receptionist so that you can be given an appointment immediately.

While there can be 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, which tend to be smaller, and in patients between the ages of 45-60 years of age where the crystalline lens is beginning to enlarge. During your routine eye exam if we observe or measure a narrowed angle, we will perform an additional examination procedure called gonioscopy. This will allow the doctor to directly examine the Trabecular Meshwork and the angle in order to carefully assess your predisposition to Angle Closure Glaucoma. By placing a special contact lens on your eye and then using the slit lamp biomicroscope to fully examine the meshwork and the angle with gonioscopy the doctor will be able to make a thorough evaluation.

In 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. Also the doctor will most likely recommend performing a type of glaucoma laser procedure in order to produce a small opening or hole in the Iris so that Aqueous Humor can drain from the eye more effectively. This procedure, called a “Laser Iridotomy”, is quite successful in treating Angle Closure Glaucoma and preventing recurrences.

If you or someone you know would like to learn more about the types of glaucoma, including chronic open angle glaucoma and closed angle glaucoma, or need an appointment for a glaucoma eye exam, please call Baltimore Washington Eye Center at 800-495-3937 to schedule an appointment.