The Queen has undergone eye surgery to remove a cataract. The 92-year-old monarch underwent the successful procedure in May.

In recent weeks the Queen has been seen wearing sunglasses at a number of events, including the Royal Windsor horse show and Buckingham Palace garden parties.

A source told the Press Association that the Queen had been treated as a day patient at the private King Edward VII’s hospital in London.

When approached, a Buckingham Palace spokesman said: “I can confirm that the Queen successfully underwent a short planned procedure to treat a cataract last month.”

The Queen did not cancel or postpone any engagements as a result of the operation.

Cataracts occur when the lens of the eye develops cloudy patches. Over time these patches can become bigger, causing blurry, misty vision and eventually blindness if left untreated.

More common in older people, a family history of cataracts can increase the risk of developing them.

The Queen Mother had an operation to remove a cataract from her left eye in 1995, when she was 95, and spent a night in hospital after the procedure.

The Queen, who is in good health, is known for her robust constitution. In 2013 she had her first hospital stay in 10 years when she had symptoms of gastroenteritis. A week of engagements, including a two-day trip to Rome, was cancelled and the Queen spent one night in hospital.

Cataract surgery involves replacing the cloudy lens inside the eye with an artificial one. It is the most common operation performed in the UK, taking 30-45 minutes, and has a high success rate.

During the operation, a tiny cut is made in the eye to remove the cloudy lens and replace it with a clear plastic one. It is often carried out under local anaesthetic and patients usually go home on the same day. It can take four to six weeks to recover.