Schematic illustration of the gaze-contingent visual aid across time at three successive instants.

<p>Note that the gray rectangle (one for each instant) shows only a small portion of the screen. Note also that only one line of text is presented here for clarity. T1/ the scotoma (outlined square) is over an empty region: the Region Of Interest (ROI) thus appears as a rectangle filled with white. The width of the ROI is constant: 16 characters. T2/ the scotoma's center is on a line of text: the ROI now highlights 16 characters whose middle location corresponds to scotoma’s center. Subjects have to decide whether or not they want to trigger an enhancement of the ROI by pressing a button. T3/ After a button press, the Region Of Augmented Vision (ROAV) appears below the scotoma while the initial ROI remains highlighted. As long as the button is pressed, the whole display remains the same and subjects can explore the ROAV with eye movements (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0174910#pone.0174910.g003" target="_blank">Fig 3</a>). After button release (not shown here), the ROAV and its corresponding ROI disappear and a new gaze-contingent ROI is displayed based on the new gaze location. In this figure and the following, the artificial scotoma is transparent for visual clarity but it was opaque in the actual experiments.</p

Potential continuation of Fig 2: visual exploration of the Region Of Augmented Vision (ROAV) with two successive ocular fixations.

<p>As long as the ROAV is displayed (i.e. as long as the button is pressed), subjects can make ocular fixations on different parts of the ROAV.</p

Example of an ROI whose left and right borders are located within words ("cette" and "complètement").

<p>Here, in contrast with the example shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0174910#pone.0174910.g004" target="_blank">Fig 4</a>, less than 50% of the rightmost word's letters are contained within the ROI, so that this word ("complètement") is not included within the ROAV. Note that the large gray rectangle shows only a small portion of the monitor’s screen.</p

Flowchart of the key principles underlying the gaze-controlled visual aid (condition 1).

<p>Flowchart of the key principles underlying the gaze-controlled visual aid (condition 1).</p

Example of ROAV adaptation to a monitor’s screen border across time.

<p>The grey rectangle represents a portion of the screen delimited by the bottom screen border (horizontal black bar). T1/ Same case as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0174910#pone.0174910.g004" target="_blank">Fig 4</a> except that the scotoma is very close to the bottom of the screen. T2/ After the button press, displaying the ROAV below the scotoma would make it invisible. Therefore, in this case, the ROAV is displayed with its center aligned with the scotoma's center.</p

Example of ROAV adaptation to a monitor’s screen border.

<p>The grey rectangle represents a portion of the screen delimited by the left screen border (vertical black bar). A/ this shows what would happen if the ROAV location was determined without taking into account the presence of the screen border: the first five letters of the word "maisons" would be invisible. B/ To allow full visibility of the ROAV, the mapping rule adjusts the ROAV location by aligning its left border with the left screen border.</p

Proportion of time spent with print sizes larger than initial size (see Fig 8A) for the 10 subjects (solid lines) as a function of the two CCTV conditions (2 and 3).

<p>Boxes represent mean proportion (middle thick line) and bootstrapped standard errors for each condition.</p

Results for subject ‘CHAR’ who had the highest reading speed mean.

<p>Symbols show reading speed (note the natural log scale) as a function of the rank of trials and for the 3 conditions (condition 1: black; condition2: red; condition 3: green). Fixed-effects are shown with dashed lines whereas the estimated random effects for this subject (i.e. the conditional means) are shown with solid lines. For visual clarity, an artificial vertical jitter was added between the lines of conditions 1 and 3 to avoid overlapping.</p