Electrodiagnostic Tests

The pattern electroretinogram (PERG) is a retinal response evoked by viewing a temporally alternating pattern, usually a black and white checkerboard or grating. The PERG is important in clinical and research applications because it provides information both about retinal ganglion cell function and, because the stimulus is customarily viewed with central fixation, the function of the macula. The PERG can therefore facilitate interpretation of an abnormal pattern VEP by revealing the retinal responses to a similar stimulus to that used for the VEP. However, practitioners may have difficulty choosing between the different techniques for recording the PERG that have been described in the literature. The International Society for Clinical Electrophysiology of Vision published a standard for clinical PERG recording in 2000 to assist practitioners in obtaining good quality reliable responses and to facilitate inter-laboratory communication and comparison. This document is the scheduled revision of that standard.

The clinical multifocal electroretinogram (mfERG) is an electrophysiological test of local retinal function. With this technique, many local ERG responses, typically 61 or 103, are recorded from the cone-driven retina under light-adapted conditions. This document specifies guidelines for performance of the test. It also provides detailed guidance on technical and practical issues, as well as on reporting test results. The main objective of the guidelines is to promote consistent quality of mfERG testing and reporting within and among centers. These 2007 guidelines, from the International Society for Clinical Electrophysiology of Vision (ISCEV: http://www.iscev.org), replace the ISCEV guidelines for the mfERG published in 2003.

To report retinal tomography and function in the course of multiple evanescent white dot syndrome (MEWDS). Prospective case series. Seven patients with unilateral MEWDS. We performed optical coherence tomography (OCT), multifocal electroretinography (mfERG), full-field electroretinography (ffERG), fluorescein and indocyanine green angiography, and visual field examinations in 7 patients with active to resolved MEWDS. OCT imaging of the posterior fundus with a 6 x 6-mm square, best-corrected visual acuity (BCVA), fundus characteristics, visual field measurements, mfERG, and ffERG responses. All patients reported unilateral blurred vision and spotty visual field defects. The fundi had yellow or white dots of various sizes and extent in the affected eyes. The visual fields had enlarged blind spots in all affected eyes and scotomas in 3 of the 7 eyes. In 5 of the all fellow eyes, 4 fellow eyes had an enlarged blind spot, peripheral visual field defects, or both; 1 eye had only a peripheral field defect. OCT showed a disrupted or irregular photoreceptor inner/outer segment (IS/OS) junction line of varied extent in 7 affected eyes and 1 fellow eye. During 1.5 weeks to 6 months follow-up (mean, 3.4 months), the BCVA returned to 1.2 along with resolution of the white dots in all eyes. The IS/OS line was restored in 7 eyes, but 1 eye had focal disruption. The visual fields returned to normal in 5 affected eyes; however, an enlarged blind spot remained in 2 affected eyes and a peripheral defect remained in 2 fellow eyes. On ffERG and mfERG, the decreased responses recovered markedly in the 7 affected eyes. The lesions responsible for MEWDS appear to disrupt the photoreceptor outer segments; morphologic and functional recovery can occur. Although the symptoms and fundus lesions were visible unilaterally, the photoreceptor dysfunction was bilateral in most cases.