Mr Farmer said, 'I thought I was going to be attacked by some hooligans. The next thing they fired a Taser at me, though I didn't know it was a Taser at the time.
'I just felt this thump in my back. As soon as the Taser hit me I hit the ground. I hit my head on the floor, then this policeman came around. I said "I'm blind, I'm blind. I'm blind".
'This policeman knelt on me and dragged my arms round my back and handcuffed me so tight I've had bruises since.'
Mr Farmer went on to say: 'I said "you're hurting me, I'm blind" - and there's no way he could not have seen my stick on the floor.
'I walk at a snail's pace. They could have walked past me, driven past me in the van, or said drop your weapon.
'They wouldn't even stop when I said I'm blind. I was absolutely terrified. I thought any second I'm going to have another stroke and this one will kill me.'
Lancashire constabulary Chief Superintendent Stuart Williams said police had received reports of a man carrying a samurai sword through Chorley.
'A description of the offender was circulated to officers and patrols were sent to look for the man,' he said.
'One of the officers who arrived in Chorley believed he had located the offender. Despite asking the man to stop, he failed to do so and the officer discharged his Taser.'