Electroretinographic information on congenital stationary night blindness for molecular biological study

There are many types of congenital stationary night blindness (CSNB) with normal fundi. Precise information on their pathogenesis can be useful for molecular biological study. We classified Schubert-Bornschein type CSNB into two types: complete and incomplete. It has been proven that these two are different clinical entities. The complete type shows no rod b-wave, and STR with normal rod a-wave on ERG, indicating that the defect lies in the rod on-bipolar cell. Cone driven ERG recorded with long flash stimuli (photopic long flash ERG) shows extremely reduced b-wave (on) with large d-wave (off), similar to the monkey ERG blocked by APB, including cone on-biopolar cell dysfunction as well. These results suggest that complete type CSNB has an "off-retina". Incomplete CSNB showed normal rod b-wave near the threshold with abnormal STR, suggesting that the rod on -bipolar cell was functioning well. The photopic long flash ERG showed small a-wave, relatively larg b-wave (on), and small d-wave (off), which resembles the monkey ERG blocked by KYN. That is, incomplete CSNB has normal rod and cone on-bipolar cells with abnormal cone off-bipolar cells, suggesting an "on-retina". The ERG findings in the mGluR6 knockout mouse are similar to those of complete type CSNB, and are useful for molecular biologic study of CSNB.