Eleanor Stollery was diagnosed with the condition in January 2015.
It is pressing on the four-year-old’s optic nerves and means she is now only able to make out changes in light or dark and no longer able to see her favourite colour – purple.
Her parents Kelly Gurney and Tim Stollery, from Alverstoke, Gosport, set up the charity Eleanor’s Voice to raise awareness of the condition and help people spot the early signs.
Since then, she has met a host of celebrities, including One Direction’s Louis Tomlinson.
But her favourite is Ed Sheeran. Last year he sent her a video message saying how happy he was that she would be attending his Wembley concert.
And now he has donated a signed guitar to Eleanor’s Voice – and it sold for £4,000 at the recent Purple Gala Ball thrown by the charity. In total, £43,000 was raised.
Kelly, 35, a credit controller, said: ‘A friend of ours contacted Ed through his management and they let him know Eleanor is a big fan.
‘He sent a video message saying he was really looking forward to seeing her at his concert which she absolutely loved.
‘Prior to the ball we thought we’d see if he would be happy to donate something to the auction.
‘We were really chuffed when he said he would donate a signed guitar. It was amazing. He is a really nice guy.’
Eleanor, who is undergoing six-week cycles of chemotherapy to keep the tumour at bay, said: ‘My favourite song is Thinking Out Loud. I really like him.
‘I had a really good time at the ball singing and dancing. I’m happy that it raised lots of money.’
Although Eleanor’s treatment is gruelling, Kelly says her daughter is ‘incredibly happy’.
She adds: ‘Eleanor is so resilient and wants to learn all the time. She is such an inspiration.’
As well as pop royalty, businesses from across the area pulled out all the stops to make the ball a success.
One of those was Onecom, in Whiteley. Aaron Brown, its chief operating officer, said: ‘We had the most fantastic night for Eleanor.
‘I am amazed by the incredible generosity of all the guests. Everyone is absolutely made-up with the final total for the evening.
‘All of those attending were totally captivated by Eleanor and her moving story. The money raised will also help support her in overcoming the challenges that she faces in the future, especially if she has to travel overseas for treatment.’
To find out more or to make a donation go to macximum.com/ers/.
You can also follow Eleanor’s story by going to @ERStollery on Twitter and by searching for Eleanor’s Voice on Facebook.