Abstract
Purpose :
Appropriate power of lens fits well for us, however, we do not have the tactics how much V1 works on wearing glasses. In this study, we used NIRS for V1 measurement, and applied recurrence plot for the obtained data to qualify and quantify the cortical activation.
Recurrence plot is a novel and simple technique for non-linear time series analysis. With two parameters (time delay and embedding dimension), given time series show the hidden characteristics in higher embedding phase space. In this study, we apply the un-threshold recurrence plot for the NIRS data, and visualize the V1 activation for the visual task.
Methods :
Two healthy volunteers participated in the experiment. Each subject had no visual nor neurological disorder except for mild myopia (about -4D (diopter)). Landolt’s rings were used in the visual acuity examination and in the experiment.
Block deign was adopted which consisted of three parts, 20 seconds of rest, 20 seconds of task and 20 seconds of rest. Five blocks were repeated in every measurement.
Subjects were asked to see the Landolt’s ring and answer the direction of the ring (i.e. visual examination) without concave lens in the rest period, and with the lens in the task period. They also asked to push the button to answer for the visual examination. In task period, we used two lens power, -1D (weak) and -3D (appropriate) and three size of visual targets, corresponding to 0.1(large), 0.3(middle) and 0.7(small) in visual acuity, so six measurements were performed for every subject. The obtained data were embedded into high dimensional phase space and constructed for recurrence plot for each measurement.
Results :
With weak power lens and small size of stimuli, cortical activation of V1 was not so clear (fig.1). On the contrary, with appropriate power lens and small size of stimuli, the activation was clear (fig.2). Scaling is same in two figs.
Conclusions :
Appropriate power of lens makes V1 activates efficiently while weak power of lens does not. With NIRS and recurrence plot, V1 activation can be visualized not only in qualitative way but also in quantitative way. This study contributes the measurements how much V1 works for targets quantitatively.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.