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Caiping Hu, Zheng Fu, Sumin Zhu, Lichun Wang, Caiping Hu; Negative electroretinograms reveal the actual value of electroretinogram (ERG) in retinal diseases. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):489.
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© ARVO (1962-2015); The Authors (2016-present)
The negative electroretinograms indicate the abnormal electrical activities of retina under brief light stimuli. As a self-proved abnormality of ERG, their causing diseases are various. The exploration of these abnormal ERG recordings with retinal lesions should expose the pathophysiological mechanisms of retinal diseases and the physiological mechanisms of ERG recordings.
The standard ERG recordings were done in our electrophysiological lab for patients with retinal diseases from 2008 to 2014, including total 116 patients. 23 patients with negative ERGs were analyzed according to the definition of negative ERG: b-wave amplitude ≤ a-wave amplitude with dark-adapted 3.0 ERG recording. Visual acuity (VA, Snellen eye chart) and visual field (VF), Optical coherence tomography (OCT) scanning were carried out for these patients. The relationship between retinal morphology and ERG recordings were analyzed in all these patients.
The 23 patients with negative ERGs had best corrected VAs from CF/50 CM to 1.2. Corrected VAs is not statistcally related to negative ERG recordings. The loss of VFs did not decide the abnormal ERG b waves, most patients with negative ERGs have relatively normal visual field ( ≥ 30 °, 18/23). The diseases included retinoschisis, congenital stationary night blindness(CSNB), early retinitis pigmentosa (RP), diabetic retinopathy (DR), and others. Morphology of retinae with negative ERGs in DR、retinoschisis showed strong relationship with the lesion of retina between inner plexiform layer (IPL) and outer plexiform layer (OPL) (7 of 8 patients). The morphology of these retinal layers had obvious damages under OCT scanning, morphologically showing the lesions of retinal bipolar cells. The non-image-forming pathways in retinal ganglion cells which produces action-potential signals through melanopsin-expressed ganglion cells can not be recorded by ERG recordings in patients with late-stage RP. As responses to transient light stimuli, the origin of ERG b waves was bipolar cells but the graded-potential-signal (ON/OFF signals) pathways for image-forming did not contribute the b waves.
CSNB and DR, early PR with negative ERGs had damaged bipolar pathways beyond the image-forming pathways, which showed the ON/OFF signals and good VAs and VFs. Negative ERGs revealed that ERG b waves show the specific functions or parallel pathways in retinal bipolar cells.
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