Central visual-field loss and driving assessment

A driver uses peripheral vision to notice events, but central and paracentral vision are needed to identify and respond to what has been noticed. A field that is wide at the edges can still be clinically concerning if loss approaches fixation.

Austroads therefore separates central-field rules from horizontal extent. This prevents the common error of treating a wide but centrally compromised field as safe simply because it reaches the horizontal threshold.

In practice, this means you should read the central 20 degrees after reliability and horizontal extent, not as an afterthought.

Austroads allows scattered single missed points in the central field and a single cluster of up to three adjoining points. These patterns may represent noise, small defects, or limited loss that does not automatically exclude an unconditional licence when all other standards are met.

The word single is important. A single cluster has a different meaning from multiple separate misses. The word adjoining is also important because a connected cluster can describe a coherent defect rather than random missed stimuli.

DRIVE Fields treats adjoining as including diagonal neighbours on the known grid. This is intentionally conservative and helps avoid under-calling connected defects.

Austroads describes significant central loss as a cluster of four or more adjoining points that is completely or partly within the central 20-degree area. It also flags a cluster of three plus any additional separate central missed points.

The clinical point is that once a central defect is larger or accompanied by other central misses, it is less likely to be random noise and more likely to affect driving-relevant detection or recognition.

Central loss that extends from a hemianopia or quadrantanopia is especially important. It should not be treated like a small isolated cluster just because the missed-point count looks similar.

A useful teaching sequence is: identify the central 20-degree zone, mark every miss inside or touching it, group adjoining misses, then ask whether the pattern is scattered, one small cluster, one large cluster, three-plus-one, or extension from a neurological pattern.

This approach is better than scanning the field and guessing. It also helps learners understand why two fields with the same number of central misses can produce different outcomes.

For an ophthalmology registrar, central field review should be linked back to anatomy: neurological hemianopic and quadrantanopic patterns behave differently from random missed points or lens artefact.

Patients may assume that peripheral field is the only driving issue. Explaining central loss can be delicate because a patient may have good acuity and still have a driving-relevant field defect.

A clear explanation is that visual acuity measures detail at fixation, while the driving-field test checks whether important areas around fixation and to the sides are reliably detected. Both matter.

If the central pattern is significant, avoid saying the patient failed because of the app. Say the visual-field pattern contains central loss that requires caution under the Austroads criteria and should be reviewed with the licensing process.

Repeat testing is reasonable when a central pattern could plausibly be artefact, the patient misunderstood the test, reliability is borderline, or the result conflicts with the clinical picture.

Escalation is appropriate when the pattern is neurological, progressive, unexplained, or high stakes for a commercial driver. In those cases, the visual-field result may also be part of broader neuro-ophthalmic or retinal assessment, not only licensing.

Keep the report proportional. A minor scattered miss does not need dramatic language. A connected central neurological pattern should not be softened into a routine pass.