Salehi Fadardi Marzieh, Bathke Arne C, Harrar Solomon W, Abel Larry Allen
*MOptom †PhD Department of Optometry and Vision Sciences, The University of Melbourne, Melbourne, Australia (MSF, LAA); Department of Statistics, University of Kentucky, Lexington, Kentucky (ACB, SWH); and Department of Mathematics, Salzburg University, Salzburg, Austria (ACB).
Optom Vis Sci. 2017 May;94(5):606-615. doi: 10.1097/OPX.0000000000001060.
Investigations of infantile nystagmus syndrome (INS) at center or at the null position have reported that INS worsens when visual demand is combined with internal states, e.g. stress. Visual function and INS parameters such as foveation time, frequency, amplitude, and intensity can also be influenced by gaze position. We hypothesized that increases from baseline in visual demand and mental load would affect INS parameters at the null position differently than at other gaze positions.
Eleven participants with idiopathic INS were asked to determine the direction of Tumbling-E targets, whose visual demand was varied through changes in size and contrast, using a staircase procedure. Targets appeared between ±25° in 5° steps. The task was repeated with both mental arithmetic and time restriction to impose higher mental load, confirmed through subjective ratings and concurrent physiological measurements.
Within-subject comparisons were limited to the null and 15° away from it. No significant main effects of task on any INS parameters were found. At both locations, high mental load worsened task performance metrics, i.e. lowest contrast (P = .001) and smallest optotype size reached (P = .012). There was a significant interaction between mental load and gaze position for foveation time (P = .02) and for the smallest optotype reached (P = .028). The increase in threshold optotype size from the low to high mental load was greater at the null than away from it. During high visual demand, foveation time significantly decreased from baseline at the null as compared to away from it (mean difference ± SE: 14.19 ± 0.7 msec; P = .010).
Under high visual demand, the effects of increased mental load on foveation time and visual task performance differed at the null as compared to 15° away from it. Assessment of these effects could be valuable when evaluating INS clinically and when considering its impact on patients' daily activities.
关于婴儿眼球震颤综合征（INS）在中心或零位的研究报告称，当视觉需求与内部状态（如压力）相结合时，INS会恶化。视觉功能以及INS参数，如注视时间、频率、幅度和强度，也会受到注视位置的影响。我们假设，与其他注视位置相比，视觉需求和心理负荷相对于基线水平的增加对零位时的INS参数影响不同。
11名特发性INS患者被要求使用阶梯法确定翻滚E字视标的方向，视标的视觉需求通过大小和对比度的变化来改变。视标出现在±25°之间，步长为5°。通过心算和时间限制重复该任务以施加更高的心理负荷，通过主观评分和同步生理测量进行确认。
受试者内比较仅限于零位及其±15°处。未发现任务对任何INS参数有显著的主效应。在两个位置，高心理负荷都会使任务表现指标恶化，即最低对比度（P = 0.001）和达到的最小视标大小（P = 0.012）。注视时间（P = 0.02）和达到的最小视标（P = 0.028）的心理负荷与注视位置之间存在显著交互作用。从零心理负荷到高心理负荷时，阈值视标大小在零位处的增加幅度大于非零位处。在高视觉需求期间，与非零位处相比，零位处的注视时间相对于基线显著减少（平均差值±标准误：14.19±0.7毫秒；P = 0.010）。
在高视觉需求下，与偏离零位15°处相比，心理负荷增加对零位处注视时间和视觉任务表现的影响有所不同。在临床评估INS以及考虑其对患者日常活动的影响时，评估这些影响可能具有重要价值。
