The attraction forms part of Dialogue Experience, a social enterprise Cheung set up in 2009 based on a model pioneered in Hamburg, Germany. It also incorporates business games for corporate work.

"Afterwards, when they come out we have a 90-minute discussion, where they reflect on their feelings and their decision-making during the games," he says of the sessions for business.

"For example, how do you measure in the dark without a ruler and without being able to see? How do they communicate with their teammates? Some people become quite controlling, but if others stay silent, they can't communicate with them."

Cheung was once in the shoes of the business executives he works with. After training as an industrial engineer, he conducted efficiency studies in factories to "squeeze the last penny out of the worker", he says.

He then helped a US Fortune 500 company expand in Hong Kong and mainland China, before moving briefly to Toronto in the late 1980s when "everyone ran away" amid uncertainty ahead of the handover. Unable to make a living, he returned and set up a packaging business that grew to have a turnover of US$120 million per year. But life changed forever in 2006, when Cheung was diagnosed with a brain tumour.

The 59-year-old took time to contemplate life and realised "making money is not my passion. I enjoy helping people. I was influenced by Bill Gates, who spends all his energy giving back."

At first, Cheung went to rural areas of the mainland to build schools, but "I felt lost because I like doing business. I stumbled across the social enterprise concept and it fitted right in".

After meeting Andres Heinecke, founder of the original German Dialogue in the Dark, he began adapting the model to suit local tastes.

"In Hong Kong people are more demanding, so I needed to speed up the exercise and create more challenges," he says.

The concept has since grown to embrace an annual concert in the dark, as well as a world first: Silence le Cabaret - a dinner and cabaret show in complete silence, performed by hearing impaired artists.

"The whole mission of this social enterprise is to embrace diversity," says Cheung. "Everyone has different strengths, and we have to learn to respect other people's diversity. Diversity is the source of innovation."

Dialogue Experience has been nominated for the Corporate Citizen Award at this year's Spirit of Hong Kong Awards, organised by the . It was nominated by local NGO Community Business, whose chief executive Fern Ngai said: "Anyone who has experienced first-hand one of Dialogue Experience's workshops or events comes away with a new perspective about people with disabilities.

"Besides the social impact of Dialogue Experience, it has been a successful business, providing a new form of experiential corporate training, and is constantly adding new experiences that are in line with its social mission."

This article appeared in the South China Morning Post print edition as: Dialogue in Dark opens eyes to world of blind