What are causes of vertical monocular diplopia? my mother & i have had this our whole lives. most noticible at close range. i have slight astigmatism.

Eye, not nerve: Can be due to irregularities in lens, but also, localized other problems in anterior eye. This can be diagnosed by an ophthalmologist.

Likely astigmatism: Monocular diplopia (double vision when only one eye is open) really only has a few causes. Uncorrected astigmatism is probably the most common of these. Other causes can be things like cataract or dry eye disease. It's pretty easy for an ophthalmologist to figure out what is going on with you so it might be worth a visit.