ERG rod a-wave in Oguchi disease.
We analyzed the change in the ERG rod a-wave waveform during the course of dark adaptation in two patients with Oguchi disease. Two Japanese patients showed a homozygous arrestin 1147delA mutation. Scotopic flash ERGs were recorded after different periods of dark adaptation. ERG rod a-waves were obtained after subtraction of the cone ERG contribution. The rod a-waves were fitted with a model of the rod receptor signal. The parameters, Rm(p3) (maximum a-wave amplitude) and S (sensitivity) were calculated. Longer periods in the dark produced larger rod a-wave but only to the first flash presented. The amplitude of the response to subsequent flashes was essentially independent of the period of dark adaptation. Rm(p3) increased with advance of dark adaptation. However, S was nearly constant. Our results suggest that the cause of delayed dark adaptation is not to be sought in the activation of phototransduction process or the regeneration of rhodopsin per se but rather in the deactivation process of the phototransduction cascade.
Usui
Tomoaki
T
Division of Ophthalmology and Visual Science, Graduate School of Medical and Dental Sciences, Niigata University, 1-757 Asahimachi, Niigata 951-8510, Japan. usuit@med.niigata-u.ac.jp
Tanimoto
Naoyuki
N
Ueki
Satoshi
S
Takagi
Mineo
M
Hasegawa
Shigeru
S
Abe
Haruki
H
Sekiya
Keigo
K
Nakazawa
Mitsuru
M
D003623:Dark Adaptation; D004596:Electroretinography; D005260:Female; D006801:Humans; D008875:Middle Aged; D009755:Night Blindness / Q000503:physiopathology*; D017948:Retinal Rod Photoreceptor Cells / Q000503:physiopathology*; D014785:Vision, Ocular