Otto Joanna M N, Bach Michael, Kommerell Guntram
Universitäts-Augenklinik, Killianstr. 5, 79106 Freiburg, Germany.
Ophthalmic Physiol Opt. 2008 Nov;28(6):550-7. doi: 10.1111/j.1475-1313.2008.00599.x.
Associated phoria is defined as the prism that aligns monocular markers in a fixation disparity (FD) test. We examined whether the 'FD-aligning prism' predicts the 'self-selected prism' (SSP), i.e. the prism that the observer judges to be most comfortable when viewing fully fusionable images.
For the FD-aligning prism, we employed a test target with a central fusion lock. To determine the SSP, identical images were shown to both eyes. The images were displayed on a cathode-ray tube monitor at a distance of 50 cm, separated for the two eyes by means of liquid crystal shutter goggles. The observer adjusted counter-rotating prisms, recorded with a potentiometer. The procedure was repeated about 1-6 weeks later.
Among the 20 non-strabismic subjects over two sessions, there were 16 instances in which the FD-aligning prism indicated a vergence position further in the eso direction than the SSP (< or =15.9 cm m(-1) = prism dioptre). In five instances, the FD-aligning prism indicated a vergence position further in the exo direction (< or =3.6 cm m(-1)). From the first to the second session, changes of > or=1.0 cm m(-1) occurred for the FD-aligning prism in 8/20 observers (< or =11.5 cm m(-1)), and for the SSP in 11/20 observers (< or =5.1 cm m(-1)).
We hypothesise that the discrepancy between the SSP and the FD-aligning prism may be attributable to the fact that the SSP was determined while the eyes were presented with identical images, whereas the FD-aligning prism was determined while the images for the right and left eyes were different in the area of the Nonius lines. The unusual experience of binocular rivalry around the Nonius lines may have influenced the vergence of the eyes. Considering the spontaneous changes observed within an interval of 1-6 weeks, in both the FD-aligning prism and the SSP, we feel that research on the repeatability of methods for prescribing prisms is indicated.
关联隐斜被定义为在注视差异（FD）测试中使单眼标记对齐的棱镜。我们研究了“FD对齐棱镜”是否能预测“自选棱镜”（SSP），即观察者在观看完全可融合图像时判断为最舒适的棱镜。
对于FD对齐棱镜，我们采用了带有中央融合锁定的测试目标。为了确定SSP，向双眼展示相同的图像。图像在阴极射线管显示器上以50厘米的距离显示，通过液晶快门眼镜将其分开供双眼观看。观察者调整反向旋转棱镜，用电位计记录。该过程在大约1 - 6周后重复。
在20名非斜视受试者的两个测试阶段中，有16次FD对齐棱镜显示的聚散位置比SSP更偏向内斜方向（<或 = 15.9厘米/米 = 棱镜度）。在5次测试中，FD对齐棱镜显示的聚散位置更偏向外斜方向（<或 = 3.6厘米/米）。从第一个测试阶段到第二个测试阶段，20名观察者中有8名（<或 = 11.5厘米/米）的FD对齐棱镜变化≥1.0厘米/米，20名观察者中有11名（<或 = 5.1厘米/米）的SSP变化≥1.0厘米/米。
我们假设SSP与FD对齐棱镜之间的差异可能归因于以下事实：SSP是在双眼呈现相同图像时确定的，而FD对齐棱镜是在右眼和左眼图像在游标线区域不同时确定的。游标线周围双眼竞争的不寻常体验可能影响了眼睛的聚散。考虑到在1 - 6周的间隔内观察到的FD对齐棱镜和SSP的自发变化，我们认为有必要对棱镜处方方法的可重复性进行研究。
