Wiggins Debbie, Woodhouse J Margaret, Margrain Tom H, Harris Christopher M, Erichsen Jonathan T
School of Optometry and Vision Sciences, Cardiff University, Cardiff, United Kingdom.
Invest Ophthalmol Vis Sci. 2007 May;48(5):2089-94. doi: 10.1167/iovs.06-1108.
To determine the effect of visual demand on the nystagmus waveform. Individuals with infantile nystagmus syndrome (INS) commonly report that making an effort to see can intensify their nystagmus and adversely affect vision. However, such an effect has never been confirmed experimentally.
The eye movement behavior of 11 subjects with INS were recorded at different gaze angles while the subjects viewed visual targets under two conditions: above and then at resolution threshold. Eye movements were recorded by infrared oculography and visual acuity (VA) was measured using Landolt C targets and a two-alternative, forced-choice (2AFC) staircase procedure. Eye movement data were analyzed at the null zone for changes in amplitude, frequency, intensity, and foveation characteristics. Waveform type was also noted under the two conditions.
Data from 11 subjects revealed a significant reduction in nystagmus amplitude (P < 0.05), frequency (P < 0.05), and intensity (P < 0.01) when target size was at visual threshold. The percentage of time the eye spent within the low-velocity window (i.e., foveation) significantly increased when target size was at visual threshold (P < 0.05). Furthermore, a change in waveform type with increased visual demand was exhibited by two subjects.
The results indicate that increased visual demand modifies the nystagmus waveform favorably (and possibly adaptively), producing a significant reduction in nystagmus intensity and prolonged foveation. These findings contradict previous anecdotal reports that visual effort intensifies the nystagmus eye movement at the cost of visual performance. This discrepancy may be attributable to the lack of psychological stress involved in the visual task reported here. This is consistent with the suggestion that it is the visual importance of the task to the individual rather than visual demand per se which exacerbates INS. Further studies are needed to investigate quantitatively the effects of stress and psychological factors on INS waveforms.
确定视觉需求对眼球震颤波形的影响。患有婴儿型眼球震颤综合征（INS）的个体通常报告称，努力视物会加剧他们的眼球震颤并对视力产生不利影响。然而，这种影响从未得到实验证实。
在两种条件下，即高于分辨率阈值然后处于分辨率阈值时，记录11名INS受试者在观看视觉目标时不同注视角度下的眼动行为。通过红外眼动图记录眼动，并使用Landolt C视标和二选一、强制选择（2AFC）阶梯程序测量视力（VA）。在零区分析眼动数据，以观察幅度、频率、强度和注视特征的变化。还记录了两种条件下的波形类型。
11名受试者的数据显示，当目标大小处于视觉阈值时，眼球震颤的幅度（P < 0.05）、频率（P < 0.05）和强度（P < 0.01）显著降低。当目标大小处于视觉阈值时，眼睛在低速窗口内（即注视）花费的时间百分比显著增加（P < 0.05）。此外，两名受试者表现出随着视觉需求增加波形类型发生变化。
结果表明，视觉需求增加会有利地（可能是适应性地）改变眼球震颤波形，使眼球震颤强度显著降低并延长注视时间。这些发现与之前的传闻报道相矛盾，即视觉努力会以视觉表现为代价加剧眼球震颤眼动。这种差异可能归因于此处报告的视觉任务中缺乏心理压力。这与以下观点一致，即对个体而言是任务的视觉重要性而非视觉需求本身加剧了INS。需要进一步研究来定量调查压力和心理因素对INS波形的影响。
