Bharadwaj Shrikant R, Hoenig M Pia, Sivaramakrishnan Viswanathan C, Karthikeyan Baskaran, Simonian Donna, Mau Katie, Rastani Sally, Schor Clifton M
School of Optometry, University of California at Berkeley, Berkeley, CA, USA.
Invest Ophthalmol Vis Sci. 2007 Apr;48(4):1592-600. doi: 10.1167/iovs.06-1018.
The maximum binocular vertical disparity that can be fused with disparity vergence (vertical-fusion amplitude or VFA), varies with convergence angle. VFA is larger for convergence responses to near than to far viewing distances; however, the clinical norms for changes in VFA with convergence have not been established. VFA at several convergence angles was measured to obtain a quantitative description of the changes in VFA with convergence.
Fifty-six adults took part in the study. Horizontal and vertical disparity stimuli were presented on a computer monitor by using the red-green anaglyphic technique. Stimulus to convergence was altered either by changing horizontal disparity on the computer monitor (experiment I: nine horizontal disparities: 1.2-22.5 PD [Delta]) or by changing the binocular viewing distance (experiment II: five viewing distances: 25-300 cm). Convergence was held constant during an experimental session, while vertical disparity was incremented in steps of 0.05 Delta after a subjective report of fusion, until the subject reported diplopia. The maximum vertical disparity that could be fused was defined as the VFA.
VFA increased linearly over the range of convergence stimuli (y = 0.10x + 1.62) and intersubject variability of VFA increased marginally with the amount of convergence. Linear regression equations with similar slopes and y-intercepts were observed in experiments I and II.
The results of the experiments provide a quantitative description of a linear relationship between VFA and convergence. The linear regression equation could be used in a clinical setting to establish norms and to screen for vertical vergence abnormalities.
可与视差性聚散相融合的最大双眼垂直视差（垂直融合幅度或VFA）随集合角而变化。近距集合反应的VFA大于远距集合反应的VFA；然而，VFA随集合变化的临床标准尚未确立。测量了几个集合角下的VFA，以获得VFA随集合变化的定量描述。
56名成年人参与了本研究。使用红绿色立体图技术在电脑显示器上呈现水平和垂直视差刺激。通过改变电脑显示器上的水平视差（实验I：九个水平视差：1.2 - 22.5棱镜度[Δ]）或改变双眼注视距离（实验II：五个注视距离：25 - 300厘米）来改变集合刺激。在实验过程中集合保持恒定，在受试者报告融合后，垂直视差以0.05Δ的步长递增，直至受试者报告复视。可融合的最大垂直视差被定义为VFA。
在集合刺激范围内，VFA呈线性增加（y = 0.10x + 1.62），VFA的个体间变异性随集合量略有增加。在实验I和实验II中观察到具有相似斜率和y轴截距的线性回归方程。
实验结果提供了VFA与集合之间线性关系的定量描述。该线性回归方程可用于临床，以建立标准并筛查垂直聚散异常。
