Narrow Angle and risks of Acute Angle Closure Glaucoma with the Objective Measurements of the Pentacam

For many years both as a resident at New York Eye and Ear Infirmary and as an attending at Harvard Medical School, it never ceased to amazed us of how patients inevitably would come in to the ER with an acute attack of narrow angle glaucoma on a late Friday or Saturday night or middle of the night when the only doctor on call was a first year resident. Usually the first or second year resident would take care of these frightened patients so as not to “wake” the attending on call. Those of us who have taken care of these patients are often the ones who really look for narrow angles in our patients since we have seen the significant consequences narrow angle (a fully treatable condition that is often left untreated). Especially with so many drugs exacerbating narrow angles on the market these days (like sleeping pills, Benadryl, and TOPAMAX® (topiramate) ), there is a real need to warn these patients of the risk of having narrow angle.

However, since there are no symptoms with narrow angles often, except sometimes a mild headache, patients become suspicious when told they have something they have never heard of before. Who can blame them? Even after showing such patients their Pentacam (a more objective scan of their angle), some really are in disbelief.

Recently a patient told me that she always got headaches every time she was dilated and could not understand why. When I told her it was from Narrow Angle she was surprised as she had never heard of this. When asked about family history she said no one in the family had any such history. Her Pentacam and Gonioscopy clearly demonstrated Narrow Angles. They were “occludable” in a dark room which means the iris tissue blocked off my view of the Trabecular Meshwork or Angle when the pupil dilated a bit and I was not pushing on the eye with the Gonioscopy contact lens instrument.

After her Laser Iridotomy, her chronic headaches went away and she never had a headache after dilation again. Interestingly, when she heard this was a genetic condition often, she went through her dad’s old medical records. She was shocked to see papers with the words “Narrow Angle” for her father and an appointment date for a Laser Iridotomy. Her dad never mentioned this to any of his kids or family.

The below handout is given to all our patients with an Anterior Chamber Depth less than 2.5mm (the standard definition of narrow angle). There are so many factors that affect risks of acute angle closure, so it is hard to determine with 100% accuracy who will have an attack and who will not. Generally, most cases are not emergencies (unless the criteria are met below which are high risk).

But personally, if I had a narrow angle, knowing the minimal risk of having it treated with a laser that takes about 5-15min in general, and knowing the devastating consequences to my vision if an attack happens, I would have the laser done very soon.

NARROW ANGLES by Sandra Lora Cremers, MD, FACS

The angle of the eye is located between the cornea (the clear window of the eye) and the iris (the colored part of the eye) where fluid (aqueous) inside of the eye drains out to the trabecular meshwork or “sink.” Some people are born with narrow, drains/angles. Some develop increasing narrowing of the angle with age as the lens of the eye grows in circumference by adding rings like a tree. In people with narrow angles, this increase in circumference encroaches on the already limited anterior segment space. If left untreated, further narrowing of the angle can causes the pressure to build up and increase the risk of Acute Angle Closure (AAC) or Closed Angle Glaucoma which can cause sudden pain and blindness. Narrow angle can also cause glaucoma (slow but permanent optic nerve damage with vision loss) and causes almost half of the blindness from glaucoma. Be sure to check all medication inserts to look for precautions in patients with narrow angles. The best way to view the angle is with an instrument called a Gonioscopy. New technology allows us to perform measurements on the angle, though the gold standard remains gonioscopy (though there is more of a subjective assessment with this instrument since if an eyeMD pushes too hard, the angle may look “open” when in fact it is narrow.)

[If you would like to know more about risk: Objective measures from the Pentacam have helped quantify risk: ACV=anterior chamber volume; ACD=anterior chamber depth; ACA=anterior chamber angle; Standard Gonioscopy is more subjective.

Normal (approx)	Narrow Angle	High risk AAC Sensitivity	High risk AAC Specificity
ACV >171mm³	≤113 mm³ =88% sensitivity, specificity significant narrow angles (Shaffer grade ≤1)	≤100 µl 93.3%	≤100 µl 100%.
ACD >3.15mm	<2.5 mm	≤2.1 86.7%	≤2.1 100%
ACA >34°	>34°	≤26° 73.3%	≤26° 88.2%

There are 3 options to main options to treat Narrow Angles:

1. Observation: if the narrow angle is minimal or is not causing any symptoms (occasional headache, brow ache, blurry vision), the angle can we watched periodically with gonioscopy (a contact lens with 4 mirrors). There, however, is a risk of sudden loss of vision and angle closure. Most eye surgeons recommend laser iridotomy or lens removal soon to avoid this uncertain risk. Either way, be sure to return for repeat gonioscopy and tell your eye surgeon of headaches, brow aches, or vision changes, especially in the evening or after dilation (after dilation starts to wear off.)

2. Laser Peripheral Iridotomy (LPI): we use a laser to make a microscopic hole in the iris to help open the angle. LPI helps prevent angle closure. It can also delay the need for lens removal if there is no significant cataract. The biggest risk of LPI is that the hole closes over time and needs to be reopened (<5). The risk of transient intraocular pressure rise, persistent inflammation, hyphema, further cataract formation, endothelial cell loss, and scar formation is very low. LPIs should be done on both eyes but are usually not an emergency. It usually takes a few minutes per eye. We give a topical anesthetic to help with discomfort. Steroid drops are given four times a day for 2-3 days after the procedure to help decrease inflammation. Rarely, the laser iridotomy is not enough and a different type of treatment is needed (iridoplasty, iridectomy or lens removal).

3. Lens removal: This offers the advantage of improving the patient’s uncorrected vision and preventing further maturation of the lens (developing a hard cataract). Lens removal or cataract surgery decreases the risk of angle closure essentially to zero. The lens never grows back. This procedure has its own risks which can be further discussed with your eye surgeon. Lens removal is the best way to remove the risk of angle closure in most patients if needed.

References for Patients:
1. Kurita N, Mayama C, Tomidokoro A, Aihara M, Araie M. Potential of the Pentacam in screening for primary angle closure and primary angle closure suspect. J Glaucoma. 2009; 18: 506–512.
2. Hong S, Yi JH, Kang SY, Seong GJ, Kim CY. Detection of occludable angles with the Pentacam and the anterior segment optical coherence tomography. Yonsei Med J. 2009; 50: 525–528.
3. Alonso RS, Ambrosio R, Junior, Paranhos A, Junior, Sakata LM, Ventura MP. Glaucoma anterior chamber morphometry based on optical Scheimpflug images. Arq Bras Oftalmol. 2010; 73: 497–500.
4. https://www.health.harvard.edu/newsletter_article/Narrow_angles_a_tip-off_to_eyesight_risk

“Narrow angles” a tip-off to eyesight risk

Published: April, 2006

Proper eye care can limit vision loss from most glaucoma — and prevent one of its most serious forms.

Glaucoma is a group of eye diseases that cause vision loss and blindness through damage to the optic nerve. Several factors contribute to its development, but the main culprit is elevated intraocular pressure, that is, pressure within the eye.

Theoretically, glaucoma can be managed and vision loss prevented or minimized with early detection and medical treatment to control intraocular pressure. But the most common form, called open-angle glaucoma, progresses so slowly and subtly that symptoms, such as blind spots and reduced peripheral vision, may go unnoticed until the disease has advanced and vision loss is inevitable.

By contrast, angle-closure glaucoma, which accounts for about 10%–15% of glaucoma in the United States, can come on suddenly and painfully and cause vision loss or blindness within hours or days. As dire as this sounds, the good news is that angle-closure glaucoma is highly preventable. For one thing, eyes that develop it have a telltale anatomical feature called “narrow angles,” which can be detected during a routine eye examination. Narrow angles means that the angle between the outer edge of the iris and the cornea is narrower, or more closed, than normal. This can affect fluid flow and thus intraocular pressure (see illustration).

Anatomy of angle-closure glaucoma

In the normal eye, a fluid called the aqueous humor circulates continuously from behind the iris (the colored part of the eye) to the front, or anterior, chamber of the eye, delivering nourishment to the lens and the cells lining the cornea (the clear part of the eye). The fluid then drains out of the eye through the trabecular meshwork — the eye’s filtration system — at the junction of the outer iris and the cornea.

In angle-closure glaucoma, the trabecular meshwork is obstructed by the iris, because the angle where the iris meets the cornea (sometimes referred to as the drainage angle) is narrower than normal. This slows or blocks the flow of aqueous humor out of the eye. Pressure from the aqueous humor behind the iris forces it against the trabecular meshwork.

Having narrow angles doesn’t mean that angle-closure glaucoma is inevitable. But the narrower the angle, the greater the risk, especially with increasing age. That’s why it’s important to know if you have narrow angles and to discuss with your clinician how you will be followed.

Who’s at risk for angle-closure glaucoma?

Shorter eyes — that is, farsighted eyes — are at greater risk because they tend to have a shallow anterior chamber (the fluid-filled space at the front of the eye), which narrows the angle between the iris and cornea. Risk is also age-related. In particular, the lens grows each year, becoming thicker from front to back. As the lens pushes forward, the angle between the iris and cornea narrows, and resistance to fluid flow between the iris and lens increases.

If fluid accumulates behind the iris, the iris may bulge forward and block the eye’s drainage system (the trabecular meshwork). This can precipitate an acute angle-closure attack. In such an attack, intraocular pressure skyrockets, causing severe eye pain and headache, blurry vision, eye redness, colored halos around lights, nausea, and vomiting. This is a medical emergency: Left untreated, high intraocular pressure can cause permanent damage within hours.

The goal of identifying people with narrow angles is to prevent an acute attack and to catch chronic angle-closure glaucoma — which develops more slowly — before damage occurs. Risk for angle-closure glaucoma is greater in farsighted people and in women because their eyes are smaller. Asians and Eskimos are also at increased risk because their eyes tend to have shallow anterior chambers.

How do I know if I’m at risk?

The best defense against all forms of glaucoma is regular eye examinations. Experts recommend that adults have a comprehensive eye exam at least twice in their 20s and 30s, every two to four years after age 40, and annually starting at age 60. If you have risk factors, such as a family history of glaucoma, your clinician will recommend screening more often. If you’ve been told you have narrow angles, you should have an eye examination every year, regardless of age.

During an eye exam, your vision will be tested for refractive error (farsightedness or nearsightedness). Peripheral vision will also be checked, as well as eye movement and coordination and intraocular pressure. Your clinician will examine the back of the eye with a hand-held device (an ophthalmoscope) or a slit lamp (a combination microscope and light). The slit lamp is also used to look at the structures at the front of the eye and to check for narrow angles.

What if I have narrow angles?

Not everyone with narrow angles develops angle-closure glaucoma. But a clinician can assess the risk by looking into the eye with a special lens (gonioprism) to examine the trabecular meshwork. If at least half of the trabecular meshwork is visible, you’re not at imminent risk and will be advised to have yearly exams. But if more than 50% is obscured, the next step is usually laser iridotomy to prevent an acute angle-closure attack.

Laser iridotomy is an in-office or outpatient procedure that uses an intense beam of light to create a tiny drainage hole at the outer edge of the iris. This ensures that fluid behind the iris can flow to the front of the eye and out through the trabecular meshwork. The procedure is quick and has few complications or side effects. Some inflammation may occur, which can be treated with steroid drops. Patients can usually return to work the next day.

The long-term safety of preventive laser iridotomy hasn’t been fully studied. But experts generally agree that the benefits far outweigh the risks: “It’s much safer than missing someone who potentially could have an attack of angle-closure glaucoma,” says Harvard Medical School ophthalmologist Dr. Claudia Richter. “Eyes that have those attacks are often never normal again.”

An attack is treated with medications to reduce the production of aqueous humor and increase drainage. After the eye has calmed down, laser iridotomy can be performed, usually within a few days. Because the other eye is also at risk, anyone who has an attack in one eye is routinely advised to have the procedure on the other eye.

Narrow-angle precautions

If you’ve been warned that you have narrow angles and haven’t had an iridotomy, keep the following in mind:

Anything that dilates the pupils can trigger an acute angle-closure attack. That’s why clinicians screen for narrow angles before they administer dilating eyedrops. Certain medications can dilate the pupils, including some antidepressants and antihypertensive drugs and a number of over-the-counter cold and allergy remedies. Check drug labels for warnings about glaucoma, and consult your pharmacist or physician before taking medications or supplements of any kind.
If you experience an upset stomach with nausea, vomiting, and a headache, cover one eye, then the other. If your vision is blurry in one eye, you may be having an acute angle-closure attack. Contact your physician immediately.