In this study, we investigated the performance of patients with homonymous VFDs in comparison with healthy-sighted control subjects during a special-offer supermarket search task. A considerable number of patients managed to pass the test despite the binocular homonymous visual-field loss. Our main finding, namely that some patients with HVFDs are able to fully compensate for their deficit, is in accordance with prior driving studies of patients with HVFDs.
18,21 No significant differences were found in the number of correctly collected items between the subject subgroups. This finding suggests that patients with HVFDs are able to perform similarly to a healthy-sighted control group if there are no time restrictions. However, this setting does not fully represent real-world scenarios, which often involve high-risk driving conditions and time pressure. Such scenarios pose a high demand on the individual and the need to scan the scene quickly and efficiently. Therefore, a time-related passing criterion based on the performance of healthy subjects was set. According to this criterion, patient groups needed on average longer time per correctly collected item (
Tc) than the respective control groups. However, a subgroup of patients completed the task within the defined time period (HPp), while patients classified as “failed” (HPf) needed significantly longer time to complete the task. Successful task performance seems to be associated with effective visual exploration; however, more data will be needed to confirm this assumption. Our results indicate that an effective compensation strategy in patients with HVFDs employs more glances beyond the 60° VF (i.e., toward the peripheral visual field). In the present supermarket search task, this visual exploration strategy is associated with successful task performance. Related studies have reported that a primary focus on the central VF is associated with better performance, due to functional specialization of the human visual field.
16,21,33 However, this finding was either related to visual search of static scenes with the use of a chin rest and a restricted field of view (29° × 22°),
16 or to an on-road driving test,
21 which is substantially different from the present experiment. During the supermarket search task, the significance of the central part of the visual scene relative to a straight-ahead position is presumably less important than the periphery, due to the eccentric location of the targets on each side of the corridor. In addition, bottom-up information processing, which is based on incoming data from the environment to form a perception, may be less pronounced in the present task than in driving tasks. Our findings are in accordance with a recent study (Tomasi M, et al.
IOVS. 2014;ARVO E-Abstract 4131), which investigated the compensatory gaze patterns of hemianopic patients when walking outside. The authors in found that hemianopes looked far peripherally (30°) from their body heading direction and directed their gaze toward the blind side significantly more often than toward the seeing side (Tomasi M, et al.
IOVS. 2014;ARVO E-Abstract 4131).