Humphrey, Medmont, Henson and other driving visual-field layouts

A perimeter is the machine or software platform. A layout is the exact set of tested points. A printout is the document the clinician uses as evidence. Confusing these three ideas is one of the fastest ways to misclassify a driving field.

A Humphrey printout can contain many strategies that are not Esterman. A Medmont printout can be a driving field or another visual-field program. A Henson driving test can use a native layout that is not identical to the Humphrey reference grid.

DRIVE Fields therefore asks for the source and pattern. It is not being fussy; it is protecting the measurement.

Austroads describes the binocular Esterman as classically performed on a Humphrey visual field analyser. That makes the Humphrey-style standard Esterman the familiar reference point for many clinicians.

The reference grid is useful because its point positions, horizontal extent behaviour, and central cluster logic can be codified. It also means clinicians can recognise common patterns and artefacts more consistently.

However, Humphrey-style does not mean every printed field from a Humphrey machine is suitable. The test strategy must still be the driving Esterman pattern, with reliability data available.

Austroads permits machines that can be shown to be equivalent, and specifically gives Medmont binocular visual field printed in level map mode as an example. Optometry Australia has also discussed the importance of recognising clinically equivalent alternatives rather than forcing every patient through a Humphrey machine.

For clinicians, the practical question is whether the specific printout gives the point pattern, reliability evidence, and driving-field output needed for the licensing question. A brand name alone is not enough.

In DRIVE Fields, Medmont support uses a native driving-field grid rather than pretending the printout is a Humphrey Esterman. That preserves the geometry and prevents misleading row-by-row assumptions.

Some devices provide driving-field tests that are clinically useful but use different point patterns or metadata. Henson 9000 Group 1 and Group 2 outputs, Melbourne Rapid Fields layouts, and other analyser pathways need explicit mapping before they can be treated deterministically.

Where the point layout has been mapped and the pathway is intentionally supported, DRIVE Fields can calculate on that layout. Where the layout, fixation evidence, or Australian licensing acceptance is uncertain, manual review is the right outcome.

This is a better user experience than a false sense of precision. A clinician can still use the app to organise thinking, but the report should say when the device pathway is not fully settled.

If the printout does not show point locations clearly, does not state the test strategy, lacks reliability metadata, or uses a custom layout, do not force it onto the nearest-looking grid. That can change clusters and horizontal extent.

The safer approach is to repeat the test on a supported driving-field pathway, request the numeric point map, or send the original printout for manual authority or specialist review.

For trainees, this is a useful lesson in digital tools generally: a precise calculation on the wrong input is still wrong.

Good limitation wording is specific. Instead of "device uncertain", say what is uncertain: point layout not confirmed, fixation monitoring not printed, false positives absent, source strategy unclear, or licensing acceptance not established.

This helps the next clinician, the licensing authority, and the patient understand what would resolve the uncertainty. It also avoids making unsupported devices sound inferior when the real issue is evidence compatibility.

The tone should stay practical and non-defensive. The aim is not to promote one perimeter over another; it is to make sure the visual-field evidence answers the driving question.