Chan H L, Siu A W, Yap M K, Brown B
Ophthalmic Physiol Opt. 2002 Nov;22(6):482-90. doi: 10.1046/j.1475-1313.2002.00052.x.
Unclear ocular media is a very common condition of older eyes characterized by significant light scattering and image degradation. The multifocal electroretinography (MERG) is a useful objective technique to measure retinal activity but its validity in the presence of cloudy ocular media remains unclear. We tested the MERG under controlled light scattering conditions using a liquid crystal diffuser (LCD) that simulated different degrees of image degradation.
The MERG were taken from 13 normal young subjects seated behind a LCD set under two conditions: scatter (visual acuity approximately 6/18) and non-scatter (visual acuity approximately6/6). The pupils had been dilated and the eyes were optically corrected for the working distance. The first-order kernel MERG response was analysed. Three subjects underwent MERG measurement with two additional intermediate light scattering levels (i.e. visual acuity approximately 6/9 and 6/12).
The macular MERG response density was reduced (p < 0.001), but the peripheral MERG response densities were increased (p < 0.001) under the scattering condition. A similar trend was also observed with intermediate degrees of light scattering. Comparing the MERG waveforms without light scattering, a new retinal response was identified with a characteristic latency of about 60 ms (P60), but it was diminished in size under the scattering conditions.
The veiling luminance might have caused the reduction in the macular MERG response and an elevation in the peripheral retina with light scatter. The functional suppression of P60 observed under the influence of light scatter may be related to retinal adaptation. Unclear optical media will affect the interpretation of MERG results.
不明的眼内介质是老年眼睛非常常见的一种状况，其特征是明显的光散射和图像退化。多焦视网膜电图（MERG）是一种用于测量视网膜活动的有用的客观技术，但其在存在混浊眼内介质的情况下的有效性仍不清楚。我们使用模拟不同程度图像退化的液晶扩散器（LCD）在受控的光散射条件下测试了MERG。
在两种条件下从坐在LCD装置后面的13名正常年轻受试者获取MERG：散射（视力约为6/18）和非散射（视力约为6/6）。瞳孔已散瞳，眼睛针对工作距离进行了光学矫正。分析了一阶核MERG反应。三名受试者在另外两个中间光散射水平（即视力约为6/9和6/12）下进行了MERG测量。
在散射条件下，黄斑MERG反应密度降低（p < 0.001），但周边MERG反应密度增加（p < 0.001）。在中间程度的光散射下也观察到类似趋势。比较无散射情况下的MERG波形，识别出一种新的视网膜反应，其特征潜伏期约为60毫秒（P60），但在散射条件下其大小减小。
遮蔽亮度可能导致了黄斑MERG反应的降低以及光散射时周边视网膜的升高。在光散射影响下观察到的P60的功能抑制可能与视网膜适应有关。不明的光学介质会影响MERG结果的解释。
