Sakata et al. should be congratulated for providing a five-year perspective on the natural history of untreated open-angle glaucoma with average intraocular pressure (IOP) of 12 mmHg in 76 eyes of 76 patients. This IOP level should not be associated with considerable trabecular meshwork dysfunction. Interestingly, in follow-up the mean IOP in these patients did not increase; nor were there IOP differences between subjects who did and did not progress.
Lower baseline IOP in open angle glaucoma produces comparable progression rates to other untreated normal tension glaucoma patients with baseline IOP that was 4-5 mm Hg higher
In their work, Sakata et al. employ carefully crafted structural and functional definitions of disease progression. Among the participants with baseline age of 53 years, there was considerable cupping (mean vertical cup-disc ratio (CDR) = 0.85), although the average mean deviation was 2.8 decibels. Patients with hard-to-read myopic or dysmorphic discs were not included in the study. Importantly, they find that the rate of progression was 66% at five years. The authors estimate that the average slope of progression on visual field was -0.33 decibels/year. Assuming no other intercurrent disease and a continued linear progression rate, most of these subjects would have advanced functional loss (MD worse than -12 decibels) and some would be visually disabled after three decades. The authors find IOP fluctuation, baseline CDR, and history of disc hemorrhage as potential risk factors for progression based on multivariable analysis.
The study was small and did not include patients with diabetes and hypertension. Systemic blood pressure was not considered as a possible risk factor for disease progression. Only two of 90 patients reported a history of migraines and no patient reported Raynaud's phenomenon. This work underscores that a lower baseline IOP in open angle glaucoma produces comparable progression rates to other untreated normal tension glau-coma patients with baseline IOP that was 4-5 mm Hg higher1,2 and that disc hemorrhage remains an important biomarker for glaucomatous progression.