Escalante Jaime Bernal, Rosenfield Mark
School of Optometry, Universidad Autonoma de Aguascalientes, Aguascalientes, Mexico.
Optometry. 2006 May;77(5):229-34. doi: 10.1016/j.optm.2006.02.006.
Measurement of the stimulus accommodative convergence to accommodation (AC/A) ratio is a standard procedure in clinical optometric practice. Typically, heterophoria is assessed at several accommodative stimulus levels, and the gradient of the vergence to accommodation function computed. A number of procedures are available for the subjective measurement of heterophoria, but it is unclear whether the use of different vergence measurement techniques will alter the obtained AC/A value. Accordingly, the current study compared AC/A ratios measured using 3 clinical subjective heterophoria tests, namely the von Graefe (VG), Maddox Rod (MR), and Modified Thorington (MT) procedures.
The AC/A ratio was measured in 60 visually normal subjects between 20 and 25 years of age using each of the 3 procedures listed above. The accommodative stimulus was varied by the introduction of +/-1.00 diopter (D) spherical lenses over the distance refractive correction while subjects viewed a target at a viewing distance of 40 cm. To examine the repeatability of each procedure, the AC/A ratio was measured on 2 separate occasions for each measurement technique, with the 2 sessions being separated by at least 24 hours.
Mean values of stimulus AC/A ratio measured using the VG, MR, and MT procedures were 3.47, 2.99, and 2.46Delta/D, respectively. These differences were significant (p=0.0001). In addition, the coefficient of repeatability for the 3 techniques was 2.22, 1.99, and 1.20 Delta/D, respectively.
Ratios obtained using the Modified Thorington technique with +/-1.00 D lenses showed the best repeatability, whereas the poorest repeatability was found with the von Graefe technique when only +1.00 D lenses were used to vary the accommodative stimulus. Accordingly, we recommend that that Modified Thorington procedure with +/-1.00 D lenses be used to quantify heterophoria during clinical measurement of the stimulus AC/A ratio.
测量调节性集合与调节（AC/A）比值是临床验光实践中的标准程序。通常，在几个调节刺激水平下评估隐斜视，并计算集合与调节功能的梯度。有多种用于主观测量隐斜视的程序，但尚不清楚使用不同的集合测量技术是否会改变所获得的AC/A值。因此，本研究比较了使用三种临床主观隐斜视测试（即von Graefe（VG）、马多克斯杆（MR）和改良索林顿（MT）程序）测量的AC/A比值。
使用上述三种程序中的每一种，对60名年龄在20至25岁之间的视力正常受试者测量AC/A比值。当受试者在40厘米的观察距离观看目标时，通过在远距屈光矫正上引入±1.00屈光度（D）的球面透镜来改变调节刺激。为了检验每种程序的可重复性，每种测量技术在两个不同的时间测量AC/A比值，两次测量之间至少间隔24小时。
使用VG、MR和MT程序测量的刺激AC/A比值的平均值分别为3.47、2.99和2.46Δ/D。这些差异具有统计学意义（p = 0.0001）。此外，这三种技术的可重复性系数分别为2.22、1.99和1.20Δ/D。
使用±1.00 D透镜的改良索林顿技术获得的比值显示出最佳的可重复性，而当仅使用+1.00 D透镜来改变调节刺激时，von Graefe技术的可重复性最差。因此，我们建议在临床测量刺激AC/A比值时，使用带有±1.00 D透镜的改良索林顿程序来量化隐斜视。
