Muir Fulton, 45, from Doonfoot, Ayr, needed a cornea transplant after both eyes became infected.
He cut short his holiday and flew home after seeking help from an eye surgeon at Ayr Hospital.
Muir went for a morning swim, forgetting he had his contact lenses in and an infection spread behind the lens.
Within hours it had begun to damage his eyes. By the next day he was struggling to see.
Muir, of Doonfoot, Ayr, went to a Spanish hospital but felt he was “getting nowhere” and, desperate, called the eye department at Ayr Hospital and spoke to eye surgeon, Mr Sathish Srinivasan.
“He told me to cut my holiday short and fly home immediately.
“I was struggling to see and knew I was going blind.”
Muir’s eyes were so badly infected that the thin membrane covering the eyeball, the cornea, was scarred by infection and blocked images passing through to the eye.
Property developer Muir’s left eye became so infected it was in danger of bursting open, he says.
He was admitted urgently to Ayr Hospital where he was given antibiotic eye drops every 30 minutes around the clock for four days.
“I was warned that if the drops did not work, my left eye would be glued shut,” Muir added.
“Mr Srinivasan’s treatment saved it but I was still blind. My family had to take me everywhere. “
Consultant ophthalmologist Mr Srinivasan said only a cornea transplant in his right eye offered hope and the chance of success was limited.
Mr Srinivasan said: “We got a donor cornea from the national eye bank and I am delighted to say it has worked, against considerable odds.
“Many people don’t know never to swim or indeed take a shower with contact lenses. It’s also easy to forget you are wearing them.”
Muir could see as soon as the bandages came off.
“It was amazing. My sight had been saved,” he said.
He is approaching the end of his 18-month treatment.
Last week he was told that he will even be able to drive in a couple of weeks.
His wife Eileen said: “I feared that Muir would be permanently blind and was on the point of calling the RNIB to assess our home and help us make it blind friendly.
“We are hugely grateful for everything that has been done.”
A spokeswoman for NHS Blood and Transplant said: “Corneas can be donated after death, no matter how old the person.”