According to Mr Hansen, unbeknownst to him, while he was under general anaesthesia, he had suffered an allergic reaction to one of the medications he was administered to stop his heart for the coronary bypass. His blood pressure had plummeted and he nearly died on the operating table. The anaesthetist fought hard to save Mr Hansen's life, before he was put in a coma for several days for his body to recover.

"When I woke up I was blind. My optic nerves had been ruined by the lack of flow of blood," he explained. "It was pretty scary".

"An anaphylactic shock, they call it: a reaction to one of the drugs. They (the medical staff) didn't know I was allergic to it and I didn't either."

There was no "light at the end of the tunnel" while his heart was stopped, he says; "Just blackness until I awoke and found that I could not see."

However, it's also more complicated than that. Even though his sight is gone, Mr Hansen continues to "see" constant, vivid imagery. These include; "absurd psychedelic patterns", "marching figures" and "ridiculous cartoon-like" people.

"It was fascinating for a while but after 24 hours I had no relief, I could not get to sleep and every time I closed my eyes I still saw the same thing," he said.

Mr Hansen would soon learn that these visualisations were a symptom of Charles Bonnet Syndrome (CBS). A condition affecting one in 5 people who have suddenly lost their vision. It is very similar to phantom-limb pain experienced by new amputees and involves constant visual phenomenon.

Soon the constantly moving patterns and shapes he was "seeing" were replaced by visions far more alarming. Dark figures with frightening faces began to "skulk at the edge of (his) vision".

The foreign shadows, which appeared to resemble people, would accost him suddenly - sometimes one at a time, sometimes in groups.

Mr Hansen became "too scared to go to sleep" and "too scared to stay awake".

Another time, he walked into his own bedroom and found it was full of people.

"I did not like the look of them. They looked sinister and I didn't know who they were," he recalled.

Fortunately, within a week of suddenly going blind, he discovered he could wield some control over the type of visions he was constantly afflicted by.

One such way was by actively telling himself the awful things he saw weren't real, by "dismissing them".

The other way was through music.

It had been more than 35 years since he had picked up a guitar, but miraculously, he began to teach himself.

For the many years prior to losing his sight, Mr Hansen had been an IT specialist - a profession which clearly gave him the expert grasp of technology that allowed him to learn guitar chords without his sight. Through various phone apps, computer programs and YouTube tutorials, he developed a system to teach himself.

It took some time and super-human patience but, after practicing and perfecting his guitar chords for six hours a day over many, many months, he could eventually play entire songs.

Then he learnt to sing and after several months of lessons with Gabe Middleton's Fit Voice Coach singing school, Mr Hansen got his younger brother Rob Hansen and old friend Doug Sloan to form a band with him.

They called themselves 'Steed', and more than a year on from commencing weekly band practice, they gave their first public performance at Word of Mouth winery on October 11.

With over 30 songs in the band's repertoire - mostly of the soft-rock, blues genre- , Mr Hansen now hopes to start gigging regularly at functions.

"We've had a lot of time to get our sound right," he said.

"But I'm my own worst critic. I always know I can be better and do better every time I sing but I'm never satisfied," he said with a chuckle.

"I'm so pig-headed about doing everything myself".