Monocular information for perceiving large egocentric distance: A comparison between monocularly blind patients and normally sighted observers

•Patients with one eye perceive large-scale egocentric depth as accurately and precisely as binocular observers.•The environment can significantly influence perceptual accuracy. Bisection was more accurate indoors than outdoors.•Optic flow generated by voluntary head movements might compensate for monocular vision loss to enable effective perception.•The perception of egocentric distance exhibited a linear relationship; accuracy decreased as the target distance increased. The debate surrounding the advantages of binocular versus monocular vision has persisted for decades. This study aimed to investigate whether individuals with monocular vision loss could accurately and precisely perceive large egocentric distances in real-world environments, under natural viewing conditions, comparable to those with normal vision. A total of 49 participants took part in the study, divided into three groups based on their viewing conditions. Two experiments were conducted to assess the accuracy and precision of estimating egocentric distances to visual targets and the coordination of actions during blind walking. In Experiment 1, participants were positioned in both a hallway and a large open field, tasked with judging the midpoint of self-to-target distances spanning from 5 to 30 m. Experiment 2 involved a blind walking task, where participants attempted to walk towards the same targets without visual or environmental feedback at an unusually rapid pace. The findings revealed that perceptual accuracy and precision were primarily influenced by the environmental context, motion condition, and target distance, rather than the visual conditions. Surprisingly, individuals with monocular vision loss demonstrated comparable accuracy and precision in perceiving egocentric distances to that of individuals with normal vision.