Asymmetric Pattern of VF Loss Found in POAG

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Researchers who previously found that primary open-angle glaucoma (POAG) and primary angle-closure glaucoma (PACG) have different patterns of visual field damage¹ now report yet another difference between the two glaucomas. An asymmetric rate of visual field (VF) loss seems to be a feature of eyes with POAG—but not those eyes with PACG.²

“This difference further promotes our understanding of mechanisms of visual field loss underlying both glau­coma types,” said Ryo Asaoka, MD, at the University of Tokyo in Japan.

Study goal. The researchers set out to determine and compare global, region-wise, and point-wise rates of VF loss in POAG and PACG eyes, with the goal of identifying whether POAG and PACG eyes progress at different rates and/or with different patterns.

To do so, they reviewed the medical records of 282 patients (440 eyes) with POAG and 49 patients (79 eyes) with PACG who were treated at two university hospitals in Japan between 1998 and 2016. All had at least six reliable visual field tests with Humphrey Field Analyzer II. Glaucoma was the only disease that caused VF damage.

Asymmetric findings. In POAG, the rate of VF loss was faster in the superior hemifield compared to the inferior hemifield, particularly in the central, paracen­tral, and peripheral arcuate 2 regions. This asymmetry was not observed in PACG eyes. “This was not neces­sarily surprising because we already knew there were considerably different patterns in visual field damage between POAG and PACG,” Dr. Asaoka commented.

In a separate finding, PACG eyes had a consistently faster global rate of VF loss compared to POAG eyes; however, this difference was not statistically significant.

Questions remain. Dr. Asaoka wants to better understand the disease mechanisms related to VF loss and how they might differ between POAG and PACG eyes.

For example, VF loss in PACG appears to be purely due to an elevated IOP, he said, whereas loss in POAG is more complex. Another possible contributing factor is corneal hysteresis; this “is very closely associated with the progression of glaucoma in POAG,” he said. In a separate study, Dr. Asaoka and his colleagues confirmed that concept in a Japanese population with a very high prevalence of normal-tension glaucoma,³ and they plan to continue to look at these contributing factors, he said.

In the clinic. Dr. Asaoka advised clinicians to consid­er that superior VF is likely to progress faster in POAG, whereas both superior and inferior hemifields can progress relatively quickly in PACG.

—Miriam Karmel

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1 Yousefi S et al. Invest Ophthalmol Vis Sci. 2018;59(3):1279-1287.

2 Yousefi S et al. Invest Ophthalmol Vis Sci. 2018;59(15):5717-5725.

3 Matsuura M et al. Sci Rep. 2017;7:40798.

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Relevant financial disclosures—Dr. Asaoka: None.

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