It happened at around 4.50pm on Station Road when the victim was walking near to Morecambe Bay Primary School close to the corner with Poulton Road.
He was approached from behind by two people – possibly a man and a woman – and hit to the side of his head causing him to fall to the floor.
They then reached across his shoulder and grabbed his bag, running off up Clarence Street and down Deansgate.
DS Ian Lawrence from Lancaster CID said: “Thankfully the victim wasn’t badly injured and the bag didn’t contain any money; however it did have various personal documents, cards, two packets of tobacco, medication and the man’s passport inside. His glasses, which he needs to see, were also damaged.
“If you have any information that could help us with our investigation, please get in touch by calling 01524 596457 or if you fail to get an answer, 101, quoting incident reference 1034 of January 30th.”
Alternatively independent charity Crimestoppers can be contacted on 0800 555111 or online at crimestoppers-uk.org.