A woman was diagnosed with a brain tumour after an optician spotted abnormalities at an eye test.
Christel Callow, 26, from Shropshire, is now raising £62,000 for proton beam therapy that is not widely available on the NHS.
She has had most of the tumour removed but has been told the therapy will target what is left more effectively than radiotherapy.
NHS England said it was only available to eligible patients.
Miss Callow had been having headaches for about two months when she booked the appointment on 22 July.
There, the opticians found pressure that had caused a haemorrhage in her right eye.
An MRI scan at Royal Shrewsbury Hospital revealed a tennis-ball sized tumour and, a week after the initial eye test, she underwent surgery at Royal Stoke Hospital.
“They said I had been living with it for a long time… if it hadn’t been found by the optician, I would have probably died, I would have collapsed or had a seizure or a stroke,” she said.
Miss Callow was told she had a fast-growing cancer called anaplastic astrocytoma, and would need radiotherapy – but the radiotherapy could damage other parts of her brain, affecting her speech and movement.
Her family researched alternatives and found proton beam therapy, which uses high energy protons precisely targeted at a tumour to treat specific types of cancer.
Miss Callow said she did not qualify for the treatment on the NHS and has been raising money to have it at the Rutherford Cancer Centre in South Wales.
NHS England said it could not comment on why a specific case may not be eligible.
Within 24 hours, she had raised more than £4,000 and friends have been arranging a fundraising event.
Miss Callow said she “never expected” the response.
“It was really emotional. I just want to thank everyone who has donated and is thinking about it,” she said.
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