Interesting question! I've been lightheaded recently too for no apparent reason... So I've just done a literature search for isotretinoin and presyncope (lightheadedness) and came up with nothing. So it seems a link hasn't been recognised, which doesn't necessarily mean there isn't one but probably does... Is there any other reason why you could be light headed? Do you think you are drinking enough water/any change in your intake? Are the episodes triggered by anything like standing for a long time, standing up too fast or an emotional stimulus? If it continues I'd recommend seeing a doctor, sorry I can't be more help.