The question posed in the present study was quite simple: is it possible for the car windscreen to act as an alternative accommodation stimulus to targets on the road ahead, thereby causing the eye to accommodate inappropriately? Initially it was necessary to establish whether typical windscreen-to-driver distances (WD) were similar to dark focus positions and use windscreens placed at these typical distances to investigate any anomalous accommodation behaviour. The characteristics of accommodation behaviour during daytime as compared to night time driving conditions were of importance. Furthermore the effects of a simultaneous task were of concern since under normal driving conditions concentration is divided between operating the vehicle and other activities such as listening to audio equipment, navigating and/or talking. It has been shown that the resting state is affected by increased mental load, anxiety, stress and cognitive demand. The variation of the resting state with these non-visual factors is thought to be due to its dependence on the aggregate inputs of the parasympathetic and sympathetic branches of the autonomic system. It may be possible that some of these effects allow the Mandelbaum effect to occur more readily under certain driving conditions. (A)
Samenvatting