Evaluation of a gaze-controlled vision enhancement system for reading in visually impaired people

People with low vision, especially those with Central Field Loss (CFL), need magnification to read. The flexibility of Electronic Vision Enhancement Systems (EVES) offers several ways of magnifying text. Due to the restricted field of view of EVES, the need for magnification is conflicting with the need to navigate through text (panning). We have developed and implemented a real-time gaze-controlled system whose goal is to optimize the possibility of magnifying a portion of text while maintaining global viewing of the other portions of the text (condition 1). Two other conditions were implemented that mimicked commercially available advanced systems known as CCTV (closed-circuit television systems)—conditions 2 and 3. In these two conditions, magnification was uniformly applied to the whole text without any possibility to specifically select a region of interest. The three conditions were implemented on the same computer to remove differences that might have been induced by dissimilar equipment. A gaze-contingent artificial 10° scotoma (a mask continuously displayed in real time on the screen at the gaze location) was used in the three conditions in order to simulate macular degeneration. Ten healthy subjects with a gaze-contingent scotoma read aloud sentences from a French newspaper in nine experimental one-hour sessions. Reading speed was measured and constituted the main dependent variable to compare the three conditions. All subjects were able to use condition 1 and they found it slightly more comfortable to use than condition 2 (and similar to condition 3). Importantly, reading speed results did not show any significant difference between the three systems. In addition, learning curves were similar in the three conditions. This proof of concept study suggests that the principles underlying the gaze-controlled enhanced system might be further developed and fruitfully incorporated in different kinds of EVES for low vision reading.

低视力人群，尤其是伴中心视野缺损（Central Field Loss, CFL）者，阅读时需借助放大工具。电子视觉增强系统（Electronic Vision Enhancement Systems, EVES）具备灵活多样的文本放大方案，但受限于其视场范围，放大需求与文本浏览（平移操作）的需求之间存在冲突。本研究开发并实现了一套实时眼控系统，其核心目标是在保留文本其余部分全局视野的前提下，最大化对指定文本区域的放大能力（条件1）。此外还设置了两个模拟商用先进闭路电视系统（closed-circuit television systems, CCTV）的实验条件，即条件2与条件3。在这两个条件中，放大效果会均匀应用于全部文本，无法针对性选择感兴趣区域。为排除设备差异带来的影响，三种实验条件均在同一台计算机上实现。本研究在三种条件中均采用了注视联动式人工10°暗点——即在屏幕注视点位置实时持续显示的遮蔽蒙版——以模拟黄斑变性。招募10名健康受试者，在实验中为其配置注视联动式人工暗点，让其在9个时长为1小时的实验时段内朗读法国报纸上的句子。以阅读速度作为主要因变量，对三种实验条件进行对比分析。所有受试者均可顺利使用条件1，且普遍认为条件1的使用舒适度略优于条件2，与条件3相当。关键结果显示，三种系统的阅读速度无显著差异。此外，三种条件下的学习曲线也较为相似。本概念验证研究表明，该眼控增强系统的核心原理可进一步开发，并有望有效应用于各类面向低视力人群阅读的电子视觉增强系统中。