I need explanation...
Spencer: “All this time you could see.” Aria: “From the very first operation.” Jenna: “Yes.” Emily: “How could you lie about this?” Jenna: “It was the only protection I had.” Hanna: “Protection from what?”
Jenna: “Someone tried to burn down our house with me in it, remember?
Jenna: If people think that you're blind, they get careless. You see what they don't think you can see.” Spencer: “And you never told Toby.” Jenna: “He was safer if he didn't know.”
The ‘Pretty-Little-Liars.wikia.com’ filed this scene under ‘Continuity’ and connects it to episode 2x23 – “Eye Of The Beholder”. [LINK]
In 2x23 Jenna was trapped in Jason‘s house when a fire started. She was rescued by Hanna.
Jenna was blinded from a fire-cracker prank by Alison which happened on July, 4th, 2009 in Rosewood-time shown in a few flashbacks.