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Hendrik P. N. Scholl, Hana Langrová, Carsten M. Pusch, Bernd Wissinger, Eberhart Zrenner, Eckart Apfelstedt-Sylla; Slow and Fast Rod ERG Pathways in Patients with X-Linked Complete Stationary Night Blindness Carrying Mutations in the NYX Gene. Invest. Ophthalmol. Vis. Sci. 2001;42(11):2728-2736.
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purpose. To study the slow and fast rod signals of the scotopic 15-Hz flicker
ERG in patients carrying mutations in the NYX gene,
which has been recently identified as the cause of the complete form of
congenital stationary night blindness, CSNB1.
methods. Twenty eyes of 11 patients with CSNB1 who had nondetectable standard
ERG rod b-waves were involved in the study. Scotopic ERG response
amplitudes and phases to flicker intensities ranging from −3.37 to−
0.57 log scotopic trolands · sec (scot td · sec) were
measured at a flicker frequency of 15 Hz. ERG signals to flicker
intensities between −3.37 and −1.97 and between −1.17 and −0.57 log
scot td · sec were considered to represent primarily the slow and
fast rod ERG pathway, respectively. Additionally, standard ERGs were
performed. Twenty-two normal volunteers served as control subjects.
results. For the slow rod ERG pathway, all patients exhibited ERG signals that
were indistinguishable from noise. Accordingly, there was no systematic
phase behavior for the slow rod signals. For the fast rod ERG pathway,
the signals were significantly above noise, but they were significantly
reduced in amplitude and advanced in phase.
conclusions. There is evidence that the slow and the fast rod ERG signals can be
attributed to the rod bipolar–AII cell pathway and the
rod–cone–coupling pathway, respectively. The current study provides
evidence to suggest that a defective NYX gene product
(nyctalopin) prevents detectable signal transmission through ON rod
bipolar cells, but there is a residual transmission through rod–cone
gap junctions in CSNB1, possibly through the OFF cone
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