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Campaigns to reduce road traffic accidents have paid little attention to the way headgear could interfere with vision. Binocular visual field measurement was undertaken in six healthy volunteers wearing four different types of anorak.
All four anoraks greatly reduced the horizontal and superior field of vision. The anorak producing the worst reduction resulted in a width of vision of 99° and only 15° of vision above eye level, versus 167° and 52° respectively without an anorak.
Anorak wearers should turn their heads to look sideways before crossing the road.
In the popular cartoon series South Park a child called Kenny wears an anorak, and during every episode he is killed. Anoraks and cagoules are trendy items among teenagers, and their hoods will narrow the visual field. Unless a conscious effort is made to turn the head, objects, particularly from the temporal fields of vision, may be missed—an effect simulating bitemporal hemianopia. We wished to document the change in visual field caused by an anorak, in the belief that it might have implications for road safety.
We measured the binocular field of vision in six healthy adult volunteers with no known eye disease, using the Aimark perimeter with a 4 mm diameter white light as the target. After baseline field measurement, each volunteer was tested wearing four different makes of anorak. The hoods were worn identically for each volunteer. The horizontal fields of vision at eye level and the superior and inferior fields of vision from the horizontal midline were compared with baseline values. The results were analysed with the two-tailed t-test, unequal variances being assumed.
Without hoods, mean horizontal field of vision was 167.3° (SD 5.4, range 158-173) and mean vertical field 51.7° (7.2, 43-62) superiorly and 66° (5.1, 60-73) inferiorly. All four anorak hoods severely restricted the visual field of each volunteer (Table 1). The mean reduction was 32% horizontally (P<0.01), 59% superiorly (P<0.01) and 3% inferiorly (P=0.42). The worst anorak in this respect reduced horizontal vision by 41% and superior vision by 71%, leaving a width of vision of 99° and only 14.8° of vision above eye level (Figures (Figures11 and and22).
The loss of visual fields caused by anorak-wearing in this study will be even more pronounced in real life when individuals walk in the rain with their heads ducked down.
In 1998, 43 500 children were killed or injured on the roads of the UK1. Of these, around 24 900 were pedestrians and cyclists. 1200 children were killed or injured within 50 m of a pedestrian crossing. Among parents of primary school children, road accidents were the greatest worry. The Department of the Environment has been trying to encourage children to walk to school2, and various child road-safety campaigns have been launched2,3. Almost nine of every ten casualties are incurred crossing the road, and in one-third of these the child is masked by a stationary vehicle3. ‘Stop, look, listen, live’ is one of the slogans to encourage safer road crossing by children, but our results show that anorak-wearers will need to make a conscious effort and turn the head. When an anorak is purchased for a child, the effects on vision deserve serious consideration.