Binocular summation of contrast remains intact in strabismic amblyopia
Binocular summation of contrast remains intact in strabismic amblyopia
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DOI：
10.1167/iovs.07-0194
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发表时间：
2007-11-01
影响因子：
4.4
通讯作者：
Hess, Robert F.
中科院分区：
文献类型：
--
作者：
Baker, Daniel H.;Meese, Tim S.;Hess, Robert F.
目的。斜视性弱视通常与几种视觉缺陷有关，包括弱视眼对比度敏感度丧失和双眼视觉异常。双眼总和比率(BSR)通常通过比较双眼刺激的对比敏感度(SENS(BIN))和仅用好眼睛测量的对比敏感度(SENS Good)来评估，得出BSR=SENS(BIN)/SENS Good。这一计算提供了临床双眼功能的可操作性指标，但不评估双眼对比总和的神经机制是否完整。本研究旨在探讨这一问题。方法：使用水平正弦波光栅作为刺激(3或9个周期/度；200ms)，并将上述常规评估方法与调整(归一化)弱视眼对比度以相等单眼敏感度的方法进行比较。结果：在9名斜视性弱视患者(平均年龄32岁)中，结果证实，使用常规方法时，BSR接近一致(很少或没有双眼优势)，但使用归一化方法时，BSR增加到约v2或更高。结果与正常对照组(n=3；平均年龄38岁)相似，并与眼睛之间对比度的生理学总和一致。当正常观察者在一只眼睛前面使用中性密度(ND)滤光器进行实验时，他们的表现在两种评估方法上都与弱视相似。结论结果表明，斜视性弱视具有双眼对比度总和的机制，双眼弱视的弱视缺陷可以用ND滤光器来模拟。讨论了这些结果对最佳临床实践的影响。
PURPOSE. Strabismic amblyopia is typically associated with several visual deficits, including loss of contrast sensitivity in the amblyopic eye and abnormal binocular vision. Binocular summation ratios ( BSRs) are usually assessed by comparing contrast sensitivity for binocular stimuli ( sens(BIN)) with that measured in the good eye alone ( sens GOOD), giving BSR = sens (BIN)/ sens GOOD. This calculation provides an operational index of clinical binocular function, but does not assess whether neuronal mechanisms for binocular summation of contrast remain intact. This study was conducted to investigate this question.METHODS. Horizontal sine- wave gratings were used as stimuli ( 3 or 9 cyc/ deg; 200 ms), and the conventional method of assessment ( above) was compared with one in which the contrast in the amblyopic eye was adjusted ( normalized) to equate monocular sensitivities.RESULTS. In nine strabismic amblyopes ( mean age, 32 years), the results confirmed that the BSR was close to unity when the conventional method was used ( little or no binocular advantage), but increased to approximately v 2 or higher when the normalization method was used. The results were similar to those for normal control subjects ( n = 3; mean age, 38 years) and were consistent with the physiological summation of contrast between the eyes. When the normal observers performed the experiments with a neutral- density ( ND) filter in front of one eye, their performance was similar to that of the amblyopes in both methods of assessment.CONCLUSIONS. The results indicate that strabismic amblyopes have mechanisms for binocular summation of contrast and that the amblyopic deficits of binocularity can be simulated with an ND filter. The implications of these results for best clinical practice are discussed.