A million partially sighted and blind people will benefit from the bequests in his will, which has just been published.
Mr Southon, of Canford Cliffs, Poole, Dorset, who was the co-founder and former chairman of the MFI Furniture Group, died aged 80 of prostate cancer last July. His will leaves most of his estate to the Royal National Institute for the Blind, Fight for Sight and the Institute of Cancer Research.
Mr Southon, who had eyesight problems, also bequeathed pounds 250,000 to the eye unit at his local hospital, the Royal Bournemouth. A further pounds 200,000 goes to the International Glaucoma Association and pounds 200,000 to the Calibre Cassette Library of Recorded Books.
The RNIB is set to receive a quarter of the estate. Andrew Essex of the RNIB said: "We are over the moon. We won't know exactly how much it is for about two years, but it is a great help with planning." Last year the RNIB went pounds 2.5m into the red because of a drop in legacies. Mr Essex added: "Another problem is the Lottery - we have had a grant of pounds 188,000, but we estimate we've probably lost pounds 500,000."
Mr Southon retired from MFI about 10 years ago. He had no children and is survived by a nephew and niece. His wife, Elsie, died at around the time he retired after suffering from Alzheimer's disease. In 1986 he set up the Southon Charitable Trust in her memory to promote research to help the elderly.
His solicitor and executor, George Perrins, of Poole, said: "Arthur Southon was a kindly man who felt strongly that he wanted to benefit charities in which he had a personal belief."
Cyril Gumbley, chief officer of East Dorset Community Health Council, said it would be benefit eye patients throughout the area.