Cataracts occur when changes in the lens of the eye cause it to become less transparent, which results in cloudy or misty vision.
What is cataract eye surgery?
Following the procedure, the Queen did not cancel or postpone any engagements, and has been seen on good form at events including the Buckingham Palace Garden Party and the Chelsea Flower Show.
The Press Association learned from a source that the Queen was treated as a day patient at the private King Edward VII's hospital in London.
Cataracts are more common in the elderly and can affect the ability to carry out daily activities such as driving.
Queen Elizabeth, 92, the world's oldest monarch, underwent successful surgery at a London hospital to treat an eye cataract last month, Buckingham Palace said on Friday.
Despite her age, the Queen is known for her robust health and still carries out hundreds of engagements every year.
A week of engagements, including a two-day trip to Rome, was cancelled and the Queen spent one night in hospital.
To treat them, the cloudy lens inside the eye is replaced with an artificial one in an operation that usually takes just over half an hour.
In 2016, she missed the annual Christmas service she usually attends with her family on her estate in Sandringham, eastern England, due to a heavy cold.
It is performed under local anesthetic and is usually concluded within 40 minutes. It can four to six weeks for patients to fully recover.