Home tonometry: pressure above target predicted field loss when clinic readings did not

Design

Retrospective analysis of longitudinal data

Population

94 treated open-angle glaucoma patients (150 eyes) with home tonometry

Primary outcome

Association of IOP metrics with visual field mean deviation slope (dB/year)

Effect

Home average IOP excess β -0.34 (p=0.003); in-office metrics not associated with progression

A retrospective analysis included 94 treated patients (150 eyes) with open-angle glaucoma of several types who had been prescribed a home tonometer. Home readings over at least 7 days and in-office readings were analysed with standard metrics and with three new threshold-based measures: percentage of readings above a threshold, average IOP excess and total IOP excess.

Mean IOP was 13 to 14 mmHg and similar between settings. No standard IOP metric was significantly associated with visual field progression. Home-derived average and total IOP excess above each patient's target were associated with faster progression, for example absolute average excess β -0.34 (p=0.003) and total excess β -0.35 (p=0.048), while in-office equivalents were not.

The design is retrospective, in 94 patients who were selected for home monitoring, and the metrics are new. The findings are a case for prospective testing, not a reason to change monitoring now. In India, access to home tonometers is limited and the cost may rule it out for most patients.

• Average pressure in clinic may hide how often pressure exceeds a patient's target.
• Home-derived excess above target tracked field progression; clinic equivalents did not.
• Consider home tonometry for patients progressing despite apparently controlled clinic IOP, where it is available.
• Validate in prospective studies before replacing office-based review.

Why it matters

It suggests that the 'controlled' pressure on a clinic reading can understate the pressure burden between visits.

Don't overread it

Retrospective, small, and the threshold metrics are new; association with progression is not proof of benefit from monitoring.

The statistics, in plain English

A negative coefficient means a faster decline in visual field mean deviation per year as pressure excess rises. With 94 patients and several metrics tested, some significant results may arise by chance, which is why confirmation in another cohort matters.

Read the rest in the app

You have read your two free briefings this month. The app carries all 27 specialties, every morning, free — and this finding is waiting in it.

Get Daily Doctor — free

Scan to keep reading on your phone. No account needed to start.