van den Berg T J, Boltjes B
The Netherlands Ophthalmic Research Institute, Department of Visual System Analysis, Amsterdam.
Doc Ophthalmol. 1987 Dec;67(4):347-54. doi: 10.1007/BF00143952.
In studies on the pattern electroretinogram the quality of the retinal image is a major concern. The use of contact lens electrodes was rejected since a good pattern could not be recorded. This is believed to be due to blurring of the retinal image. As indicator of image quality the patient's visual acuity is often used. We wondered whether this is a sufficient criterion. The retinal image is the product of the whole optical point-spread function of the eye whereas visual acuity refers only to the central portion of this function. On the basis of existing reports it can be estimated that for the young normal eye the outer edges of this function (straylight) causes considerable loss of contrast. The strength of the straylight can be much greater in older eyes. We studied the relation between the point-spread function including straylight and the pattern electroretinogram in normal eyes and some pathological cases. The measurements proved to follow the calculated contrasts on the basis of a local luminance model, with the exception of enhancement (tuning) around 60' checksize for the young normal eye. Because of the considerable differences in straylight in an older population one has to take into account that loss of pattern electroretinogram can be suffered in patients with otherwise good visual acuity.
在关于图形视网膜电图的研究中，视网膜图像的质量是一个主要关注点。由于无法记录到良好的图形，所以摒弃了使用隐形眼镜电极的方法。据信这是由于视网膜图像模糊所致。作为图像质量的指标，患者的视力常常被采用。我们想知道这是否是一个充分的标准。视网膜图像是眼睛整个光学点扩散函数的产物，而视力仅指该函数的中心部分。根据现有报告可以估计，对于年轻的正常眼睛，该函数的外边缘（杂散光）会导致相当大的对比度损失。在老年眼中，杂散光的强度可能会大得多。我们研究了包括杂散光在内的点扩散函数与正常眼睛及一些病理病例中的图形视网膜电图之间的关系。测量结果证明，除了年轻正常眼睛在60'视标大小附近的增强（调谐）情况外，测量结果遵循基于局部亮度模型计算出的对比度。由于老年人群中杂散光存在相当大的差异，必须考虑到在视力原本良好的患者中可能会出现图形视网膜电图的损失。
