The Effect of Simulated Central Field Loss on Street-crossing Decision-Making in Young Adult Pedestrians

Abstract

Significance: This study explored the street-crossing decision-making performance of young normally sighted subjects with simulated central field loss (CFL). The results suggest that using eccentric viewing enables a person to make safe and reliable street-crossing decisions.

Purpose: This study tested the hypothesis that, as the diameter of an experimentally induced central scotoma increases, the accuracy and reliability of street-crossing decisions worsen.

Methods: Street-crossing decisions were measured in 20 young subjects aged between 23 and 31 years while monocularly viewing a nonsignalized, one-way street for different vehicular arrival times. Using a 5-point rating scale, subjects judged whether they could cross the street before vehicular arrival with habitual vision and simulated CFL with eccentric viewing. The CFL was induced using soft contact lenses with different central opaque diameters. Using receiver operating characteristic curve analysis, we obtained subjects' accuracy (amount of time in seconds where subjects either overestimated or underestimated vehicular arrival time relative to their actual crossing time) and reliability (how quickly subjects transitioned from judging insufficient to sufficient time to cross relative to their actual crossing time).

Results: The centrally opaque contact lenses induced central scotomata with a mean (standard deviation) diameter of 17.12° (5.83°). No significant difference in street-crossing accuracy (P = .35) or reliability (P = .09) was found between the normal, habitual vision and simulated CFL conditions. No statistically significant correlations were found between scotoma diameter and the accuracy and reliability of subjects' street-crossing decisions (P = .83 and P = .95, respectively).

Conclusions: The findings of this study suggest that adopting eccentric viewing enables a person to successfully mitigate the negative effects of an absolute central scotoma on the accuracy and reliability of their street-crossing decisions.

Figure 1.

Street-crossing accuracy (measured as Bias in seconds) under normal habitual vision and simulated central field loss (CFL) with eccentric viewing (EV) conditions. The solid circles are individual subject data points which have been jittered to improve visualization. The lower and upper T bars represent the minimum and maximum values and the line bisecting the boxes represent the median.

Figure 2.

Street-crossing reliability (measured as the slope at the x-intercept of subjects’ non-linear function) under normal habitual vision and simulated central field loss (CFL) with eccentric viewing (EV) conditions. The solid circles are individual subject data points which have been jittered to improve visualization. The lower and upper T bars represent the minimum and maximum values and the line bisecting the boxes represent the median.