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MANAGING OPEN ANGLE GLAUCOMA

(-0.60dB/yr), highlighting the fact that progression rates may change over time. Further, progression did not occur
in all individuals: after 6 years, approximately 75% of the HTG cohort and 56% of the NTG cohort progressed. In
stark contrast, 93% of those with exfoliation syndrome progressed.
17
The CNTGS looked at the natural history of untreated glaucoma with IOP under 21mmHg and found a progression
rate similar to that of the EMGT: 50% of eyes with NTG showed deterioration within 5 to 7 years. Again, most pro-
gressed slowly, but the rate of deterioration ranged considerably from -0.2dB/year to -2.0dB/year, the latter being a
catastrophic pace that is likely to result in significant functional impairment in a relatively short time. 18
An important take-home message from these studies is that while eye care providers need to be vigilant, decisions
need not be made hastily when managing POAG. Even without treatment, progression takes years to develop in most
patients. As long as the practitioner is watching each patient closely to ensure that they are not one of the minority
that will progress rapidly, diagnosis and treatment decisions can be made over several visits. If rapid progression is de-
tected, more frequent follow-up and aggressive treatment is mandated. That being said, it is important and comforting
to note that most patients with POAG will do quite well with diligent monitoring and thoughtful treatment.

“SCREENING” FOR POAG IN THE PRIMARY EYE CARE EXAMINATION

Let’s begin with the conclusion: the best way to screen for glaucoma is through a comprehensive primary eye care
examination: assessing case history and risk factors, examining the anterior segment, measuring intraocular pres-
sure, examining the optic nerve head complex, performing a thorough fundus examination to rule out confounding
disease, and follow with guided ancillary structural and functional testing when clinically indicated. 20

Any single procedure or instrument in isolation lacks the sensitivity (identifying true positives) and specificity
(identifying true negatives) to accurately diagnose glaucomatous optic neuropathy. In the context of a compre-
21
hensive examination, however, the whole becomes far greater than the sum of its parts.
A detailed case history, entrance testing, and refractive analysis will reveal risk factors for glaucoma and guide subse-
quent examination procedures. Clinicians should be especially vigilant in the presence of the following risk factors:
• increased age 22
• African-North American or Hispanic ethnicity (for open-angle glaucoma) 23
• Asian ethnicity (for normal tension and angle-closure glaucoma) 16,24
• family history of glaucoma in first-degree relative(s) 12
• history of blunt ocular trauma and/or topical steroid use 25,26
• longstanding diabetes 27
• obstructive sleep apnea (OSA) 28
• extremes of blood pressure (particularly systemic hypotension, which may result
from aggressive treatment of systemic hypertension) 29
• hypothyroidism: Thyroid disorders may increase the risk of glaucoma 30
• myopia (in a “dose-response” relationship for open-angle glaucoma) 31
• hyperopia (for angle-closure glaucoma) 32
Although these risk factors certainly inform diagnostic decision-making, they do not in and of themselves constitute
a diagnosis.
A careful anterior segment examination facilitates identification of relatively common risk factors for glaucoma including:

• narrow angles (Van Herick assessment of angle width)
• pigment dispersion (mid-peripheral iris transillumination defects; pigment on anterior
segment structures including anterior lens and corneal endothelium)
• exfoliation (exfoliative material on the anterior lens capsule after dilation; iris transillumination
defects at the pupillary margin)

CANADIAN JOURNAL of OPTOMETRY | REVUE CANADIENNE D’OPTOMÉTRIE VOL. 79 SUPPLEMENT 1, 2017 7