PRIMARY ANGLE-CLOSURE GLAUCOMAAlso known as narrow-angle glaucoma, Dr. Carolina Valdivia explains that primary angle-closure glaucoma is the second-most common type of the disease. When my examination shows evidence of glaucoma in a patient, I next need to determine the specific type of glaucoma she or he has in order to develop an appropriate treatment plan. The first step is to determine if the patient's glaucoma is being caused by a secondary source, such as an injury or other disease process (e.g. diabetes, high blood pressure, or the use of medications containing steroid preparations). DIAGNOSING PRIMARY ANGLE-CLOSURE GLAUCOMA If my examination rules out that the patient's problem is a secondary glaucoma, I then determine the type of primary glaucoma that she or he has. For this, I need to assess if the angles formed by the cornea and the iris in the front part of the eye (anterior chamber) are closed or if they are open. The technical term for this angle is the iridocorneal angle (denoted by red brackets in the figure below). I ascertain the state of the iridocorneal angle through
gonioscopy,
a test that allows me to visualize the anterior chamber in detail.
The anterior chamber of the eye is filled with a fluid called aqueous humor. This substance constantly is produced from the blood in a structure called the ciliary body. It circulates first through the posterior chamber of the eye. This is the small space directly behind the iris but in front of the lens. It then enters the anterior chamber through the pupil and ultimately is returned to the bloodstream through the trabecular meshwork and Schlemm's canal(follow the blue line in the figure). The main problem in primary glaucoma is that intraocular pressure increases because too much aqueous humor has accumulated in the anterior and posterior chambers of the eye. In primary angle-closure glaucoma (PACG), the iridocorneal angle narrows and interferes with normal circulation of aqueous humor. This increases intraocular pressure and, if left untreated, causes ongoing damage to the optic nerve. When iridocorneal angles are within normal range, several structures can be seen in the anterior chamber through gonioscopy. These are highlighted in yellow in the figure below.
 Who is at risk for primary angle-closure glaucoma?Although anyone can be diagnosed with PACG, there are some characteristics that make people more susceptible than others. Major risk factors for PACG include:
How many people get PACG?For every 1,000 people, approximately 50 of them will have narrow iridocorneal angles. But only 10% of those 50 (or 5 individuals out of 1000), will have iridocorneal angles that are so narrow that it results in PACG.
What are the symptoms of primary angle-closure glaucoma?It depends on whether the PACG is chronic or acute. In chronic PACG, people often do not perceive any symptoms at all. In some cases, they may notice redness of the eye, discomfort, blurred vision, or a headache, the intensity of which often is reduced with sleep. If you have any of these symptoms, you should visit an ophthalmologist.
Although chronic primary angle-closure glaucoma often does not present with any symptoms noticeable to patients, particularly in its early stages, it is important that you understand that angle closure in the anterior chamber of the eye is a serious problem that must be treated as soon as possible. The following figure presents conditions of the eye that are associated with angle closure.
ACUTE PRIMARY ANGLE-CLOSURE GLAUCOMA Unlike chronic PACG and many other types of glaucoma, acute PACG presents with recognizable symptoms that often are very intense. The most common among these is severe pain that is constant and deep. It may occur suddenly and patients often describe it as the worst pain that they have ever experienced. The quality of the pain is constant, meaning that it does not improve spontaneously, and it is deep because it can be felt around the entire eye. In fact, patients have reported pain so profound that it radiates into the middle of the face on the affected side and is accompanied by nausea and vomiting. Another common symptom is decreased visual acuity. Blurring often occurs and vision loss can be significant. If the time elapsed since the start of the crisis has been short and the intensity of the pain not too extreme, decreases in visual acuity can improve in the next few days under treatment. However, if the time elapsed since the start of the crisis is significant, vision loss may be irreversible. Seeing color halos around lights is another symptom that can accompany primary angle-closure glaucoma, both in its acute and chronic forms. Other reported symptoms include excessive production of tears (lacrimation) and excess sensitivity to light (photophobia).
I am a 35-year-old woman and my mother has been diagnosed with narrow-angle glaucoma [PACG]. Five years ago, I visited an ophthalmologist because of redness in my right eye, accompanied by some discomfort. My eye also had a whitish discharge. The doctor told me that I was suffering from conjunctivitis. He prescribed some eye drops and the problem cleared up after a few days. But I am worried that this might have been an early sign that I am developing narrow-angle glaucoma like my mother. What should I do? Primary angle-closure glaucoma typically does not occur in people younger than 40 years. Although there are no absolutes in medicine, only on rare occasions do we see PACG in patients under 40 years and these usually involve some type of trauma. The episode you describe occurred when you were 30 years old. It is unlikely that it was a sign that you might be developing narrow-angle glaucoma. It is much more plausible that it was an episode of infectious conjunctivitis as your ophthalmologist diagnosed. This was confirmed by the fact that your symptoms cleared up after using the prescribed eye drops for a few days. PACG would require ongoing treatment, including the possibility of surgery. MECHANISM OF PRIMARY ANGLE-CLOSURE GLAUCOMA The most common mechanism of primary angle-closure glaucoma is something called a pupillary block. This happens when there is contact between the lens of the eye and the iris, causing the pupil to be fixed in one position (medium diameter) and it cannot open or close in order to adjust to light. Once this contact occurs, fluid called aqueous humor is unable to pass out of the anterior chamber through a structure known as the trabecular meshwork. Looking at the figure of the normal eye below (left side), the anterior chamber has depth and there is no contact between the iris and lens. The blue arrows show the direction in which the aqueous humor fluid leaves the eye after being generated in the ciliary body.
The lenses of young people are very flexible and therefore pupillary block does not normally occur in people under 40 years of age. But as we grow older, the lens of the eye becomes more rigid and loses some of its accommodation capability. Accommodation refers to the capacity of the lens to adjust in order to see objects at different distances, both close and far away. This is the reason why people above age 40 more often need corrective lenses. In eyes that are predisposed to PACG, there is an increase in the thickness of the lens and advancement.
Closure of the anterior chamber angle is a serious event and needs to be addressed immediately. In addition to redness, the cornea may look cloudy or show evidence of edema (bulging due to fluid retention). Abnormalities of the cornea can lead to blurred vision, photophobia, and excessive production of tears. The most dangerous situation for the occurrence of acute PACG is when the pupil is at a medium diameter. This means that it is not really open wide or closed to a small point. Some situations in daily life in which this happens is when we are in a semi-dark room or if we are in a stressful situation.
In my last checkup with an ophthalmologist, he recommended that I have a laser iridotomy because I am at risk for acute primary angle-closure glaucoma. I am worried about having eye surgery.Your ophthalmologist must have concluded through gonioscopy that the anterior chamber of your eye shows evidence that a narrow-angle occlusion (blockage) could develop. This might be because the anterior chamber is shallow, the cornea has a diameter that is smaller than normal, or that the lens is thicker than normal. Rather than wait for an attack of acute PACG, which will involve extreme pain and could result in permanent vision loss, it is a much better to prevent this from happening by having the iridotomy now. Laser iridotomy is a simple procedure in which a small hole is made in the iris to help facilitate the flow of aqueous humor from the posterior chamber of the eye to the anterior chamber.  Remember, in eyes that are predisposed to PACG, the lens advances forward and causes aqueous humor to accumulate behind the iris. This pushes the iris forward so that the trabecular meshwork is blocked, which in turn causes an increase in intraocular pressure. The small hole created by the laser iridotomy enables aqueous humor, which has been accumulating in the posterior chamber of the eye and raising intraocular pressure, to enter the anterior chamber. Flow of aqueous humor into the anterior chamber pushes the iris back away from the trabecular meshwork, allowing the fluid to escape and lower intraocular pressure.Acute primary angle-closure glaucoma is an emergency situation that must be seen by a physician as soon as possible. If you experience any of the the symptoms described here, especially pain in your eye, you should see a physician immediately.
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