Hayley Davidson's optician spotted the abnormality during a routine check-up at a mobile service in Thurso in September.
The 28-year-old mother only made the appointment because her daughter Rosie, two, needed her glasses repaired.
John Shanley noticed the life-threatening swelling on her optical nerve, which could have killed her if left untreated. Mr Shanley referred Ms Davidson to her doctor urgently.
Ms Davidson said: "I was sent for a CT scan. I had a cyst on my brain and the doctor said I needed surgery immediately.
"I had to travel with paramedics in an ambulance as they were concerned that I could pass out or have a fit. I was just eager to have the surgery with the wedding and Christmas coming up."
She had the operation to drain the cyst on October 3 and made it back home nine days later. She got married on December 28.
She said: "My surgeon is happy with my recovery.
"He thinks I have had the cyst since birth but something happened which caused it to swell."
The cyst grew to be 7cm-wide and crushed the left side of her brain, reducing her peripheral vision and giving her headaches.
Ms Davidson added: "If I hadn't been to see John, I would have gone blind and then I would have died. That test was life-saving."
Mr Shanley said: "The fact it had been an ongoing problem set off alarm bells. There was swelling on her optic nerve which I found suspicious."