Detectives said a group of three or four suspects, who wore gloves and had their faces covered, made off with a small amount of cash after the “despicable” attack.
They targeted the house in Hornchurch, east London, between 8.30pm and 9pm on Saturday, entering through the back door.
The burglars let off fire extinguishers in the faces of the pensioners, and also cut the man’s hand with a weapon, thought to be a screwdriver. He was later taken to hospital as a precaution.
The woman, who was not injured, was pushed to the floor and forced to stay behind a chair as her partner was asked about money in the house.
The Metropolitan Police said the raiders spoke with what may have been Eastern European accents.
There have been no arrests and detectives are appealing for information.
Trainee Detective Constable Ciara Arthur said: “It is despicable that these callous individuals attacked an elderly couple in their home while the vast majority of Londoners are either working hard to keep each other safe or simply isolating to protect themselves and others.”