Any medics around? I'm 22ish weeks pregnant and currently in the middle of my second episode of eye weirdness - shimmering type blind spot right in front of my eyes. Have done some googling (difficult!) and internet seems to think that it's most likely to be pre-eclampsia but I have low BP, not high 
Any other ideas? Should I be worried? Second pregnancy so not due to see MW again for about a month. First episode was couple of weeks ago, comes on very suddenly and wears off after 30-40 min but annoying in the meantime. Have very vague memories of this happening last time round but may be wrong about that (low BP throughout/no pre-eclampsia last time).
TIA (and apologies for typos!) :)