hi bert, that's interesting, looking through lsj it looks like there isn't a present active [face=SPIonic]ei1dw
[/face] (it's an assumed form, based on other tenses of the verb).
the aorist 2 of that "assumed" verb serves as aorist to [face=SPIonic]o(ra&w
so the verbs are locked together. if they left it blank that might not be obvious, and in particular it'd make greek composition harder, if you were trying to track down the aorist of [face=SPIonic]o(ra&w
this lsj link explains more:
http://www.perseus.tufts.edu/cgi-bin/pt ... 3D%2330876