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Patients with POAG, PACG lose visual field differently
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A study comparing eyes with primary open angle and angle closure glaucoma showed significant differences in the pattern of visual field loss between the two types of disease.
Specialists at Tokyo University Hospital and Ryukyus University Hospital, Japan, reviewed the visual field (VF) tests of 440 eyes of 283 patients with primary open angle glaucoma (POAG) and 79 eyes of 49 patients with primary angle closure glaucoma (PACG), with the aim of determining whether the two types of glaucoma progress at different rates and with different patterns.
A minimum of six tests were acquired over a mean follow up of 7 years.
PACG eyes had an overall faster global rate of VF loss (-0.29 db/year) as compared with POAG eyes (-0.23 dB/year), but the difference was not statistically significant.
Progression rates, the authors noted, were slow in both groups, reflecting the fact that glaucoma was well controlled in these patients, under treatment in a hospital setting.
Despite the similar mean total deviation (mTD) at baseline, there was a significant superior-inferior asymmetry in the rate of VF loss in the Glaucoma Hemifield Test (GHT) central, paracentral and arcuate two regions of eyes with POAG. The rate of VF loss was faster in the superior than in the inferior hemifield, and particularly in the central, paracentral and peripheral arcuate two regions. This asymmetry was not observed in eyes with PACG, suggesting that this is a characteristic pattern of VF loss of POAG and not PACG.
“This novel finding could further promote our understanding of mechanisms underlying both glaucoma types,” the authors concluded. – by Michela Cimberle
Disclosure: The authors reported no relevant financial disclosures.
Perspective
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Derek MacDonald, OD, FAAO
In noting asymmetric patterns of VF loss, Yousefi and colleagues remind us that angle closure glaucoma and open angle glaucoma are different diseases, with unique mechanisms, natural histories and treatments. This distinction is critical: Worldwide, ACG represents one of every four diagnoses, but is responsible for one of every two cases of glaucoma-related blindness. Unfortunately, it’s also overlooked: In North America, OAG is diagnosed 32 times more frequently than ACG.
Definitively identifying narrow angles requires gonioscopy; however, direct angle assessment is documented less than half the time at both diagnosis of, and preceding surgery for, glaucoma. Indirect (van Herick) assessment, even when performed by experienced clinicians, fails to detect one in three narrow angles and definitely misses peripheral anterior synechiae and secondary mechanisms. Further, as many as one in 10 patients referred for cataract surgery have undetected narrow angles, and a similar proportion referred for OAG actually have ACG.
Gonioscopy is simultaneously one of the most essential and omitted components of caring for all patients with glaucoma, particularly those who are women, older, hyperopic, Asian, developing cataract or with exfoliation, all recognized risk factors for ACG.
I’m guilty as charged, but resolving to change in 2019. How about you?
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