Department of Optometry, College of Health Science, Kangwon National University, Samcheok, Gangwon, Republic of Korea.
Optom Vis Sci. 2020 Mar;97(3):218-226. doi: 10.1097/OPX.0000000000001483.
Prism-induced convergence and vertical vergence for maintaining binocular fusion induced postural instability to a greater extent than diplopic conditions. This finding has important implication in relation to postural control of patients with large exophoria or vertical phoria in optometric clinic.
The purpose of this study was to examine whether binocular single vision with prism-induced horizontal and vertical vergence and diplopia might affect the static postural stability.
Forty-two subjects with a mean ± standard deviation age of 23.79 ± 2.81 years were enrolled in this study. To simulate convergence and divergence, base-in and base-out (BO) prisms of 4 and 8 Δ were added, respectively. To simulate vertical vergence, vertical prism of 2 Δ was added in a trial frame that corrected for the subject's refractive error during far distance (6 m) gaze. The prism power necessary to break fusion in each subject was detected and applied to induce diplopia in horizontal and vertical directions. Indices of general instability and sway power were measured under visual conditions using Tetrax and compared with normal viewing without the prism. Correlations between general instability indices and the ranges of break point in convergence and divergence were analyzed.
Postural instability was increased significantly when convergence induced by BO 4 and 8 Δ and vertical vergence induced by 2 Δ were stimulated. The correlation coefficient between ranges of BO break point and indices of general instability was -0.308 in the BO 4 Δ and -0.306 in the BO 8 Δ condition.
Although binocular input is recognized as an important factor in postural stability, binocular input with excessively stimulated convergence and vertical vergence during a far distance gaze is a latent factor affecting postural stability. On the other hand, diplopia did not influence postural stability.
棱镜诱导的会聚和垂直聚散度比复视条件更能维持双眼融合诱导的姿势不稳定。这一发现对大外斜视或垂直斜视患者在视光诊所的姿势控制具有重要意义。
本研究旨在探讨棱镜诱导的水平和垂直聚散度以及复视对静态姿势稳定性的影响。
本研究纳入 42 名平均年龄为 23.79 ± 2.81 岁的受试者。为了模拟集合和发散，分别加入了 4 和 8 Δ 的基底向内和基底向外（BO）棱镜。为了模拟垂直聚散度，在矫正远距（6 m）注视时受试者屈光不正的试镜架中加入了 2 Δ 的垂直棱镜。检测每个受试者打破融合所需的棱镜力，并将其应用于水平和垂直方向上诱导复视。在 Tetrax 下测量视觉条件下的总体不稳定指数和摆动功率，并与正常视觉时不使用棱镜进行比较。分析总体不稳定指数与会聚和发散断点范围之间的相关性。
当刺激 BO 4 和 8 Δ 引起的会聚和 2 Δ 引起的垂直聚散度时，姿势不稳定显著增加。BO 4 Δ 条件下的 BO 断点范围与总体不稳定指数之间的相关系数为-0.308，BO 8 Δ 条件下的相关系数为-0.306。
尽管双眼输入被认为是姿势稳定性的一个重要因素，但在远距离注视时过度刺激会聚和垂直聚散度的双眼输入是影响姿势稳定性的潜在因素。另一方面，复视并不影响姿势稳定性。
