On the problem of driving license driving in patients with homonymous hemianopia – legal and neurological-visual parameters

Zangemeister WH: in: fitness to drive in neurological diseases, ed. Ch Dettmers and C Weiller, Stuttgart 2004; pp.260-265 – Book Text.

Original text language: German

The starting point for our assessment must be the current legal situation. This stipulates that the perimetrically ophthalmologically evaluated visual field examination with static / dynamic target points in a non-moving patient should not exceed a field of view limitation of approximately 70 ° on one side. This results from the fact that the loss of an eye with an assumed total field of view horizontally of 190 ° (= ± 95 °) is allowed for driving a motor vehicle; i.e. 120 ° visual field of one eye is sufficient.  On the other hand, less than 120 ° is no longer sufficient, as is usually the case with homonymous hemianopsia, namely 95 ° in this approach.

Not included in this evaluation are the  neuro-visual parameters that are relevant for the driving of motor vehicles. These include the expression of hemianopia (with or without so-called sparing of the fovea) with or without inclusion of the central 10 to 15 °, that is  a more peripheral hemianopsia. Assessment of eye and head motor availability, assessment of visual, saccadic and effective motor latency, assessment of attenz and cognition in general, as far as it becomes visually relevant.

From this it follows that the previous legal regulation has the advantage of a simple and clear regulation. However, it also turns out that this simple and clear regulation is an artificial simplification of conditions, which can be differentiated with current means and also partially treated. This is also reflected in the considerable differences that exist within the EU in this regard. Thus, the legal situation e.g. in Belgium is better adapted to the reality in this respect.

What are the reasons for and against licensing hemianopic drivers?

Against the granting of a driving license speaks essentially that a complete blindness of 70 ° to one side, in both quadrants, or in either of them, in moving traffic  leads to non-seeing or ignoring obstacles or generally moving important targets. This also applies if all other mentioned parameters such as cognition and attention or reaction times are in order.

In our view, there are a number of reasons for granting a restricted driving license: A significant reason is the objection that the current regulation is based on undifferentiated diagnostic statements. It is based on a purely ophthalmological static examination of the visual field, in which head movements are not allowed. This is obviously an unnatural situation that does not arise in normal everyday driving. So  the learning drivers are told to actively turn their  head to the left before overtaking maneuvers to overcome the blind spot in this way.

Overall, it follows from the above considerations that the previous regulation requires a more differentiated shaping. The limited granting of a driving license to patients with hemianopia should therefore be linked to corresponding preliminary investigations with quantification of the data for reaction times, attention, neuro-ophthalmological assessment of gaze coordination, in addition to driving tests on the simulator or on road. The considerations presented here only for hemianopsia patients can also be analogously presented for patients with other visual, in part also acoustic and head motor deficits.