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MANAGING OPEN ANGLE GLAUCOMA

curvature, point of iris insertion, and the results of indentation. 138,139 A modification of the Scheie system noting
the most posterior visible angle structure in each quadrant and a qualitative description of iris approach and
abnormalities including peripheral anterior synechiae (PAS), angle recession, pigmentation, neovasculariza-
tion, etc. may be most applicable to clinical practice.
140
Qualitative assessment of pigment in the trabecular meshwork (TM) is critical. Increased trabecular pigmentation
is most commonly secondary to pigment dispersion (often in young myopic males) or exfoliation (often in elderly
Caucasian females). Noting the location of iris transillumination defects (mid-peripheral in pigment dispersion,
adjacent to the pupil margin in exfoliation) or the presence of exfoliative material on the anterior lens capsule, pupil
margin, and in the angle will help in the differential diagnosis. As noted in Appendix 1, the inferior angle is the
141
normally the widest while the superior is the narrowest: if less than half of the TM across more than six clock hours
(180 ) is visible, the angle is considered at risk of closure.
°
Clinical Recommendations for gonioscopy:
• Gonioscopy is a critical but often overlooked element in the assessment of all patients at risk for or
diagnosed with any type of glaucoma

• Practice makes perfect. Start practicing routinely: being familiar with normal variation facilitates the
identification of abnormal findings, and provides the experience to confidently employ the technique when
clinically indicated

ANGLE CLOSURE GLAUCOMA (ACG)
A primary angle-closure suspect (PACS) will have ‘normal’ intraocular pressure and healthy optic nerve
head (no disease), but 180 of non-synechial angle closure: routine monitoring is indicated. Individuals who
°
progress to primary angle closure (PAC) will have elevated IOP (≥21mmHg) and/or PAS accompanying iri-
dotrabecular contact, but no evidence of glaucomatous optic neuropathy: prophylactic laser peripheral iri-
dotomy (LPI) is normally recommended. Primary angle-closure glaucoma (PACG) is diagnosed in the pres-
ence of glaucomatous optic neuropathy (GON) with at least six clock hours of iridotrabecular contact and
elevated IOP. Prompt treatment including LPI augmented by medication and/or surgery (including cataract
extraction) is indicated in the presence of GON. 142,143

PACG, while more common in East Asia, is under-diagnosed in Western populations, and is responsible for
a disproportionate amount of significant vision loss. It is categorized according to gonioscopic assessment
of the amount of iridotrabecular contact obstructing the pigmented TM. 144

Classic signs and symptoms of an acute angle closure (AAC) attack include conjunctival injection, extreme
IOP elevation (often ≥40mmHg), corneal edema, blurred vision, eye pain, and vomiting. AAC is a true ocular
emergency that necessitates immediate intervention to prevent significant vision loss within hours. Inden-
tation gonioscopy may open an appositionally closed angle and allow aqueous to enter the TM, lowering
IOP. Medical therapy, decreasing aqueous production through the use of topical (beta-blocker, carbonic
anhydrase inhibitor, and alpha agonist) and oral (acetazolamide) agents, should be initiated immediately. A
topical steroid is often required, as AAC is invariably accompanied by significant inflammation. In a phakic
eye with PAC only, topical pilocarpine is indicated to break pupillary block: miotic agents are only effective
after the IOP drops and pressure-induced ischemia of the iris sphincter resolves. Once the acute attack has
been broken and the eye is quiet, bilateral LPI (that may be accompanied by laser peripheral iridoplasty and/
or cataract extraction in the involved eye) is the definitive treatment. 145-147

CANADIAN JOURNAL of OPTOMETRY | REVUE CANADIENNE D’OPTOMÉTRIE VOL. 79 SUPPLEMENT 1, 2017 19