I was asked by an adjacent pax to close my window shade because the light was blinding her. We had just taken off from DFW and it was already dark. We were headed to DCA. I asked her what outside the plane at altitude could blind her? She said she had an eye condition. I suggested that she use her sunglasses. She said she didn't have any. If she were so light sensitive I could not imagine her not having sunglasses.