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Multifocal ERG findings in complete type congenital stationary night blindness
1Department of Ophthalmology, Nagoya University School of Medicine, 65 Tsuruma-cho, Showa-ku, Nagoya 466-8550, Japan. kondomi@med.nagoya-u.ac.jp
Purpose:
To study the multifocal electroretinogram (mfERG) in patients with the complete type of congenital stationary night blindness (cCSNB), which is thought to be due to a defect in neurotransmission from the photoreceptors to the ON-bipolar cells.
Methods:
mfERGs were recorded with the VERIS recording system from four patients with cCSNB, none of whom had nystagmus. The stimulus array consisted of 61 hexagons, and the total recording time was approximately 4 minutes. The amplitudes and implicit times of the first- and second-order kernels of the local responses were compared with those from 20 myopic controls. Waveforms of the summed response from all locations were also compared between the two groups.
Results:
The first-order kernels of the mfERGs of cCSNB patients had normal amplitudes but delayed implicit times for nearly the whole field tested. The second-order kernel was severely attenuated in amplitude in cCSNB patients. The ratios of the second- to first-order kernel amplitudes were significantly reduced in cCSNB and clearly separated the cCSNB group from the control group without any overlap of the values.
Conclusions:
The second-order kernel, which is involved in adaptative mechanism of the retina to repeated flashes, is selectively reduced in cCSNB. The delay of the implicit times of the first-order kernel in patients with cCSNB may be related to the severe amplitude reduction of the second-order kernel.