The relevance of stereopsis for motorists: a pilot study

Purpose: To study the influence of stereoscopic depth perception on automob ile driving performance. Methods: Ten patients with strabismus and defectiv e stereopsis were compared with ten healthy controls with respect to their performance in a series of automobile driving manoeuvres. The two groups we re individually matched as to age, annual miles driven, years of licence ho lding and type of vehicle owned. After an ophthalmologic examination the su bjects in each group performed the following series of driving tests: (1) s topping in front of an obstacle, (2) reversing into a parking space, (3) dr iving through a slalom course, (4) estimating the relative positions of two cars. All tests were performed binocularly and monocularly (with the non-d ominant eye covered). Results: Only in the slalom test did the normal subje cts perform significantly better than the stereo-deficient subjects (odds r atio 10.5; P<0.01). In estimating position, normal subjects actually perfor med significantly worse (odds ratio 0.091; P<0.01). A significant distance ratio of 2.5 (95% CI 1.1-5.5; P=0.033) of the monocular with respect to the binocular performance of the normal subjects was found for the stopping ta sk only, while the subjects with defective stereopsis showed no difference between their monocular and binocular performance. Conclusion: In this stud y, stereopsis had a positive effect on driving performance only in dynamic situations at intermediate distances.