Techniques for treating narrow angle glaucoma

Clinicians have a variety of tools at their disposal to treat narrow angle glaucoma, according to Sunita Radhakrishnan, MD, who provide an overview of these possibilities during the Glaucoma Symposium CME at the 2016 Glaucoma 360 meeting.

To diagnose primary angle closure, the American Academy of Ophthalmology’s (AAO) Preferred Practice Pattern recommends looking for contact between the iris and the anterior chamber angle at the posterior trabecular meshwork or an anterior structure.

In early stages, clinicians should see 180º of iridotrabecular contact, but the eye is otherwise normal, said Dr. Radhakrishnan, who is with of the Glaucoma Center of San Francisco. In the next stage, physicians should see elevated intraocular pressure (IOP) or peripheral anterior synechiae (PAS). This stage is termed primary angle closure.

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But clinicians should only use the term “glaucoma” when they also see glaucomatous optic neuropathy, she said. Dr. Radhakrishnan pointed out that acute angle closure crisis may or may not lead to glaucoma. 

‘Look for it’

Noting that clinicians “won’t see it until you look for it,” Dr. Radhakrishnan recommended looking for angle closure with gonioscopy in every patient. She recommended periodic gonioscopy in phakic patients, even those with open angles in the first assessment.

“With time and with the development of cataracts, some of these patients will develop angle closure that requires intervention,” Dr. Radhakrishnan said. “So it’s important to monitor them.”

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This approach provides direct visualization of the angle structures, is quick and inexpensive, and affords 360º evaluation of the angle width, she said.

As treatment, the AAO Preferred Practice Pattern recommends considering iridotomy in primary angle closure (PAC), in acute angle closure crisis (AACC), in the fellow eye in an AACC, and in primary angle-closure glaucoma (PACG). The AAO guidelines say it “may be considered” in the case of and PAC suspect.

Factors to be considered include the extent of angle closure, the refractive error, the anterior chamber depth and lens position, the use of ocular or systemic medications that may provoke papillary block, and difficulty in accessing eye care.

Discuss with patients

Discuss with patients 

If iridotomy is not done, clinicians should discuss with patients the symptoms of an acute angle closure crisis and which medications to avoid.

There is no way to predict which PAC suspect patients will have an acute attack, said Dr. Radhakrishnan. While these attacks are not common, they can be devastating. On the other hand, the relative risk of laser iridotomy is low. So it’s important to involve the patient in the treatment decision, she added.

In an iridotomy, the elimination of the papillary block results in a flat iris profile. The goal of the treatment is to reverse the iridotrabecular contact, control the IOP, and prevent or reduce damage to the optic nerve.

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Its efficacy depends on the stage of the disease, and the mechanism of angle closure, said Dr. Radhakrishnan. She pointed out that laser peripheral iridotomy eliminates only the papillary block.

While most patients who are a PAC suspect don’t need any further intervention, clinicians should continue to monitor them after laser peripheral iridotomy. Up to a third have residual angle closure due to a non-pupillary block.

When patients have elevated IOP after laser peripheral iridotomy, a range of additional treatments may be considered, said Dr. Radhakrishnan. She listed medications, laser trabeculoplasty, iridoplasty, clear lens extraction, cataract surgery, glaucoma surgery, and combined cataract and glaucoma surgery as options.

Phaco influence on glaucoma

Phacoemulsification alone achieves a 13% reduction in IOP in primary open-angle glaucoma, 20% in exfoliative glaucoma, 30% in primary angle-closure glaucoma and 71% in an acute angle closure crisis, she said. The reduction in need for glaucoma medication follows a similar pattern.

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Because of these results, clear lens extraction in primary angle closure is under study with the EAGLE trial in the United Kingdom and East Asia.

However, Dr. Radhakrishnan counseled caution to performing phacoemulsion in patients with advanced optic nerve damage, or who are already receiving maximum tolerated medical treatment, and in those patients with small eyes.