Upon comparing visual field progression rates in three subgroups of glaucoma—primary angle-closure glaucoma (PACG), primary open-angle glaucoma (POAG) and juvenile open-angle glaucoma (JOAG)—a team of Indian researchers found that differences in fast, catastrophic visual field progression exist despite small changes in median progression rates. They note that this highlights the importance of considering the full shape of the progression rate distribution when comparing the risk of devastating visual field loss.

The team assessed 525 eyes of 525 glaucoma patients treated in an Indian tertiary care setting with at least four visual field assessments and determined progression rates. The main outcome measures were the proportions of fast (<−1.0 to −2.0 dB/y) and catastrophic (<-2.0dB/y) visual field progression. The team then compared their data with published data from a large clinical cohort in Canada.

The proportion of fast and catastrophic progressors in this cohort was less than half that of the Canada dataset (2.3% vs. 5.8%), the researchers observed, despite median progression rates differing by only 0.03dB/y. They note that PACG, POAG and JOAG represented 45%, 32% and 12% of the cohort, respectively, and baseline mean deviation values were similarly distributed between these subtypes. They add that all subtypes showed a similar distribution for progression rates, with median progression rates of -0.03dB/y, -0.05dB/y and 0.02dB/y for PACG, POAG and JOAG, respectively, and combined proportions of fast and catastrophic progression rates did not significantly differ between subtypes.

“Differences in fast and catastrophic visual field progression may occur between cohorts with similar median progression rates,” the study concluded. “Three common glaucoma subtypes within a single cohort have similar rates of fast and catastrophic progression. These results highlight the importance of considering the full shape of the distribution when assessing progression rates, as patients with rapidly deteriorating fields are among those whose management is the most challenging and urgent.”