The Mind Cannot Go Blind: Effects of Central Vision Loss on Judging One's Crossing Time

This study explored whether people with AMD can accurately judge the time they need to cross the street. The results suggest that AMD-related vision loss does not affect a person's ability to estimate his/her own street-crossing time, whereas familiarity with the street does.

The purpose of this study was to assess whether people with AMD could judge accurately their street-crossing time.

Fifty-one AMD subjects and 47 age-matched normally sighted subjects (controls) estimated their time to cross a single-lane, one-way street four times (pre-estimate). Then, subjects actually crossed the street four times and subsequently estimated their crossing time four additional times (post-estimate). A linear mixed model with repeated measures for subject was used to determine if the ratio between subjects' estimated and actual crossing times changed as a function of subject group (AMD vs. control) and whether estimates changed before and after actually crossing the street. Univariate correlations and multiple regression analyses were also performed to determine which of the measured experimental variables were the best predictors of a subject's ability to estimate his/her crossing time.

No significant difference in crossing ratios were found between the AMD (average, 1.05) and control (average, 1.16) subjects (P = .11). This was true for both the pre-crossing (AMD, 1.09; controls, 1.23; P = .11) and post-crossing ratios (AMD, 1.01; controls, 1.09; P = .17). Both subject groups' crossing ratios, however, decreased significantly going from pre to post (P < .0001). Increased age, longer actual crossing time, and experience gained from previously crossing the street resulted in less overestimation of one's crossing time.

Our data suggest that familiarity with the street as opposed to central vision loss from AMD affects a person's ability to estimate his/her crossing time.