Glaucoma is a term used to describe a group of eye disorders. It is caused by extreme pressure in the eye. Most people suffer few symptoms from glaucoma and the symptoms that do arise are typically not noticeable until the disease has progressed. However, there are instances in which glaucoma symptoms are acute and an indication of a medical emergency.
Glaucoma damages the optic nerve and eventually leads to peripheral vision loss and blindness. More than two million people in the United States are affected by glaucoma and the number is expected to increase by about a third in the next decade.
There are six different types of glaucoma, the first being the most common. They include: primary open-angle glaucoma, narrow-angle glaucoma, normal-tension glaucoma, pigmentary glaucoma, secondary glaucoma, and congenital glaucoma.
Symptoms of Narrow-Angle Glaucoma
Narrow-angle glaucoma is different from other forms of the disease because symptoms can occur suddenly. It happens when the iris (the colored part of the eye) is pulled or pushed out of place. This blocks the drainage angle of the eye. This blockage causes the eye’s internal pressure to spike, which damages the optic nerve.
Symptoms of narrow-angle glaucoma can last for hours or until the blockage is reduced and they include:
- Eye pain
- Halos around lights
- Dilated pupils
- Red eyes
- Vision loss
- Vomiting and nausea
Attacks of these symptoms are recurrent and typically cause a portion of a person’s peripheral vision to be lost. Developing acute symptoms associated with narrow-angle glaucoma is considered a medical emergency. The pressure must be reduced or a person is at risk for permanent blindness. If you are unable to reach your ophthalmologist, head to the nearest hospital emergency room.
If your narrow-angle glaucoma symptoms are chronic, it is not considered an emergency and is more like other forms of the disease. Vision can be damaged over time, but there is no sudden onset of severe symptoms and vision is affected over time.
Several factors increase a person’s risk for developing narrow-angle glaucoma.
- Age. It is more common as a person ages because the lens inside of the eye gets larger. This increases the risk for the pupil to create a blockage. The anterior chamber of the eye also becomes shallower, so the drainage angle can narrow.
- Race. There is some evidence that certain groups have an increased risk for the disorder. For instance, Asians and Inuits naturally have narrower anterior chambers, so their risk is increased.
- Sex. In the Caucasian race, more women than men develop narrow-angle glaucoma.
Causes of Narrow-Angle Glaucoma
There are several factors that contribute to the development of narrow-angle glaucoma. All of them create abnormal positioning of the iris and affect drainage of fluid in the eye. Causes include:
1. Iris Plateau
Iris plateau occurs when the iris is attached too close to the trabecular meshwork, which is where drainage occurs. As dilation of the pupil occurs, the tissue around the iris tissue bunches in the drainage angle and creates a blockage. This type of attack typically occurs when the pupil dilates in dim lighting or if eye drops are used to enlarge the pupils.
2. Pupillary Block
This occurs when the aqueous humor eye fluid produced in the ciliary body behind the iris does not flow easily through the pupil into the anterior chamber of the eye. Problems occur when the back of the iris adheres to the lens inside of the eye and blocks the pupillary channel. The fluid backs up and pushes the iris forward, causing it to close the drainage angle.
Angle closure can be a problem for people who are farsighted because they have shallow anterior chambers and narrow angles.
If a tumor develops behind the iris, it can trigger swelling of the ciliary body and alter the shape of the eye. Odds for developing narrow-angle glaucoma are also increased after a person undergoes detached retina surgery.
Treatments for Narrow-Angle Glaucoma
To treat narrow-angle glaucoma, the pressure causing problems to occur must be reduced. This is the primary goal of all treatment methods. There are several options for treatment. These include:
- Oral and intravenous medications
- Topical eye drops
- Laser and non-laser glaucoma surgery
Penetrating Glaucoma Surgery
There are several different types of glaucoma surgery. They include:
- Laser Trabeculoplasty. This surgery uses a laser to increase the outflow of internal eye fluid by creating tiny holes where the cornea meets the iris. Selective laser trabeculoplasty is able to achieve the same results with very little heat damage to the nearby tissue.
- Trabeculectomy and Trabeculotomy. This procedure removes a portion of tissue and creates a controlled leakage of fluid by installing a valve in the eye. It is the most common form of non-laser surgical treatment. A trabeculotomy is the same as a trabeculectomy, but the incisions are made without removing any tissue.
- Iridotomy and Iridectomy. Iridotomy uses a laser to create a hole in the iris, which allows drainage to occur through the blockage. An iridectomy removes a piece of the iris so fluid can flow easier when a person is suffering from narrow-angle glaucoma.
- Shunts and Stents. These devices are inserted into the eye during the surgical procedures and allow fluid to flow, alleviating problems with pressure. The devices are typically made from silicone, biocompatible metals, or polypropylene. They are sometimes referred to as glaucoma implants, though this term can also be used to described surgically implanted devices that release glaucoma medication into the eye automatically.
Non-penetrating Glaucoma Surgery
Finally, there are several less invasive techniques that can be used to improve drainage and prevent pressure from building. They include superficial incisions, so a patient experiences fewer risks and complications.
Two examples of non-penetrating glaucoma surgeries include:
- Deep Sclerectomy. A small portion of the sclera is removed with a minimally invasive incision.
- Viscocanalostomy. An opening is created and a highly pliable, gel-like material known as viscoelastic is inserted into the opening. This provides enough space so adequate drainage can occur.