A preferred retinal location of fixation can be induced when systematic stimulus relocations are applied

Abstract

Patients with central vision loss obtain visual information by fixating on an object eccentrically with a preferred retinal locus of fixation (PRL). Patients do not always choose the most efficient PRL position, and as a consequence, visual performance is not always fully exploited. This study investigates whether PRLs can be induced by applying systematic stimulus relocations. The PRL was trained using a central scotoma simulation in 15 healthy subjects. They performed different visual tasks during four sessions, after which their reading performance was evaluated. In five subjects the stimulus was relocated to the left hemifield whenever a saccade would place the stimulus on the opposite hemifield. In five different subjects the relocation was inversed: The stimulus was located in the right hemifield. The relocation was 7.5° of visual angle and it was applied horizontally. Five additional subjects naturally chose the PRL location. They were used as the control group to evaluate the development of a PRL. After training, subjects performed visual search tasks on static stimuli. Evaluation after training showed that systematic stimulus relocations can be used to influence the development of the PRL. These results might be significant for the development of training strategies for the visually impaired.

Transfer of an induced preferred retinal locus of fixation to everyday life visual tasks

“…Fifteen participants took part in the study, five males and 10 females aged between 24 and 33 years (mean: 26.6 years). Every participant had a developed PRL, acquired under simulation of central scotoma after four training sessions (Barraza-Bernal et al, 2017). Five participants had a PRL induced in the left hemifield; five different subjects had a PRL induced in the right hemifield.…”

“…Figure 1 shows the sequence of experiments performed on the study. The gray box represents the training that subjects performed prior to the performance of this experiment (Barraza-Bernal et al 2017). To develop a PRL, subjects underwent a visual task in which a single saccade target was presented at a time.…”

“…In a previous study, we showed that the PRL location can be induced at a specific hemifield when systematic stimulus relocation is applied to a stimulus that evokes saccadic eye movements (Barraza-Bernal, Rifai, & Wahl, 2017). Patients with central scotoma present a strong tendency to develop a PRL in the left side of the visual field (Cummings & Rubin, 1992;Fletcher, Schuchard, Livingstone, Crane, & Hu, 1994;Fletcher & Schuchard, 1997;Sunness, Applegate, Haselwood, & Rubin, 1996); however, in contrast to this observation, other PRL positions were proven to be beneficial for the performance of some visual tasks (Chung, Legge, & Cheung, 2004;Deruaz, Whatham, Mermoud, & Safran, 2002;Frennesson & Nilsson, 2007;Guez et al, 1993;Petre, Hazel, Fine, & Rubin, 2000;Whittaker & Lovie-Kitchin, 1993).…”

“…In our previous study, a PRL was induced to be either on the right or on the left hemifield. A stimulus that evoked a saccadic eye movement was always relocated to the induced hemifield when the saccadic Citation: Barraza-Bernal, M. J., Rifai, K., & Wahl, S. (2017). Transfer of an induced preferred retinal locus of fixation to everyday life visual tasks.…”

“…Hence, in reality central vision loss patients are challenged to perform a diversity of visual tasks in their natural environment. Taking this into account, the present study addressed the question whether the PRLs induced in Barraza-Bernal et al (2017) can be transferred to other important visual tasks. The transfer of the left-induced group, rightinduced group, and the group without inducement procedure was analyzed separately using means and standard deviations of the distance between trained and transferred PRL.…”