Queen Elizabeth II watches the racing as she attends the Epsom Derby at Epsom Racecourse. Photo / Getty Images
The Queen has undergone eye surgery to remove a cataract, wearing sunglasses in public rather than cancel her long-planned engagements.
The 92-year-old monarch underwent the successful procedure in May, Buckingham Palace confirmed on Friday afternoon.
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, reports Daily Telegraph UK.
It emerged on Friday that the Queen was 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."
It was business as usual for the head of state, who did not cancel or postpone any engagements.
The Court Circular, the public record of the working life of the Royal family, shows no major break in the Queen's work in May, from receiving official visitors at Buckingham Palace to attending the wedding of Prince Harry and Meghan Markle with the Duke of Edinburgh, who had recovered from a hip replacement operation.
There was a short gap between May 4, when she held an investiture, and May 15 when she undertook a series of jobs including hosting a garden party and welcoming the President of the Republic of Turkey and Mrs. Erdogan to the palace.
Cataracts are when the lens, a small transparent disc inside the eye, develops cloudy patches. Over time these patches usually become bigger causing blurry, misty vision and eventually blindness, if left untreated.
Cataracts are more common in the elderly and can affect the ability to carry out daily activities such as driving.
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 but, unlike her daughter, she spent a night in King Edward VII's Hospital after the surgery.
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, at the age of 86, she suffered symptoms of gastroenteritis and missed an engagement in Swansea.
A week of engagements, including a two-day trip to Rome, was cancelled and the Queen spent one night in hospital. She usually attends hospital for an annual routine check-up.
Cataracts occur when changes in the lens of the eye cause it to become less transparent, which results in cloudy or misty vision.
This can prevent someone from driving, undertaking work that requires fine detail and recognising faces.
Surgery to remove and replace the affected lens with an artificial one is the most common surgical procedure carried out on the NHS.
Around 390,000 cataract surgeries take place each year in England and 16,000 in Wales, according to the eye research charity Fight for Sight.
The condition most commonly affect adults as a result of ageing. Most people start to develop cataracts after the age of 65, but some people in their forties and fifties can also develop them.
Cataracts, which can affect one or both eyes, are a major cause of sight loss. But the surgery is a straightforward procedure that usually takes 30 to 45 minutes.
It is often carried out as day surgery under local anaesthetic, meaning the patient can go home the same day.
During the operation, the surgeon makes a tiny cut in the eye to remove the cloudy lens and replaces it with a clear plastic one.
On the NHS, patients are offered monofocal lenses, which have a single point of focus - either near or distance vision.
Those going private, like the Queen, can choose either a multifocal or an accommodating lens, which allows the eye to focus on both near and distant objects.
Most people will need to wear glasses for some tasks, like reading, after surgery regardless of the type of lens they have fitted.
It can take four to six weeks to fully recover from cataract surgery. If cataracts affect both eyes, two separate operations are required, usually carried out six to 12 weeks apart.
The risk of serious complications developing as a result of cataract surgery is very low.
Worldwide, cataracts are the leading cause of blindness, according to The International Agency for the Prevention of Blindness, for which the Queen's daughter-in-law the Countess of Wessex is a global ambassador.
Some 65 million people across the globe have been left blind or with moderate to severe visual impairment due to the condition.
The Queen is known for her robust health. Her son the Duke of York once described her as being incredibly fit for her age, and the 92-year-old monarch still rides her Fell ponies at Windsor, and drives, mainly around her private estates.
She has called time on her overseas travels, leaving long-haul destinations to the younger members of her family. But she still has a busy diary of events, and in 2017 carried out 296 engagements.
In November 2017, the Prince of Wales led the nation in honouring the country's war dead on Remembrance Sunday at the Cenotaph.
It was the first time that the Queen, as head of state, had watched the ceremony from a nearby balcony, and was seen as a sign of the royal family in transition and an acknowledgement of her age.
Just before Christmas 2016, the Queen and the Duke of Edinburgh both fell ill with heavy colds, forcing them to delay their trip to Sandringham by a day.
The Queen was not well enough to attend the Christmas Day service at St Mary Magdalene church and also missed the New Year's Day one. She later described it as a "particularly grisly mixture of cold and flu".
She turned 90 in 2016 and, the same year, used the lift rather than stairs to enter Parliament for the State Opening, avoiding the 26 steps of the royal staircase at the Sovereign's Entrance.
Buckingham Palace said the "modest adjustment" to arrangements were made for "the Queen's comfort". The decision was attributed to the Queen suffering from knee pain.
In 2014, the Prince of Wales stood in for the Queen for part of the Order of the Bath service to avoid her having to make an extra journey up and down some steep steps in full regalia.
In November 2013, the Duke of Cambridge stepped in to represent the Queen at an investiture ceremony after she suffered some "mild discomfort" with her ankle after a busy weekend of engagements including the service of remembrance at the Cenotaph.
Her first hospital stay in 10 years came in 2013 when she was 86 after she suffered symptoms of gastroenteritis and missed an engagement in Swansea when she was due to present St David's Day leeks to the 3rd Battalion The Royal Welsh.
On March 3 2013, she was admitted to King Edward VII's Hospital to be assessed. A week of engagements, including a two-day trip to Rome, was cancelled.
The Queen spent one night in hospital and left thanking staff and smiling before being driven to Buckingham Palace to rest.
It was thought her public appearances were back on track until Buckingham Palace announced on the morning of the Commonwealth Day Observance service on March 11 that she regrettably could no longer attend "as she continues to recover following her recent illness".
It was the first Commonwealth Day Observance service she had missed in 20 years, the last occasion being when she had flu in 1993.
The Queen, who placed great importance to her role as Head of the Commonwealth, did however attend the Commonwealth Reception at Marlborough House on the evening of March 11 to sign the new Commonwealth Charter.
Buckingham Palace insisted it was just the "tail end" of the symptoms and that her condition had not worsened.
But the next day she cancelled her engagements for the rest of the week, with her son, the Duke of York, saying later that it was sensible not to risk her coming out, but that she was not ill.
Her illnesses have been few and far between over the years. She has suffered from back pain, and also had operations to remove torn cartilage from both knees.
She caught measles when Prince Charles was two months old in 1949 and had to be separated from her baby son.
The first time the Queen was actually admitted to hospital was in July 1982 when she had a wisdom tooth extracted at the King Edward VII Hospital in central London.
The Queen's no-fuss approach to injury and illness was perfectly illustrated in 1994. She broke her left wrist when her horse tripped during a ride on the Sandringham estate in Norfolk.
The break was not diagnosed until almost 24 hours later when her arm was X-rayed and set in plaster at a hospital.
It was the first time she had fallen in many years and the Queen had simply brushed herself down, remounted her horse and trotted on back to Sandringham.
Why eight hours a night is the sweet spot for sleep.