What to know about cataract surgery, the eye treatment that MrBeast said cured the blindness of 1,000 people

• YouTuber MrBeast recently shared a video about restoring sight in 1,000 blind people.
• The online star collaborated with a philanthropy to provide the cataract surgeries.

A collaboration between YouTuber MrBeast and a nonprofit organization dedicated to eye care has restored the sight of 1,000 blind people with cataracts — and caused a social media firestorm.

The world's biggest YouTube star, whose real name is Jimmy Donaldson, interviewed ophthalmologist Jeff Levenson and filmed patients' reactions to seeing clearly again.

"Half of all the blindness in the world is people who need a 10-minute surgery," Levenson said in the video.

Cataracts are the leading cause of blindness and visual impairment in the world, accounting for around 40% of global blindness, according to the International Agency for the Prevention of Blindness (IAPB).

The treatable condition begins as a cloudy area on the lens of the eye, caused by the proteins in the lens clumping together. This most often occurs due to old age, but can also be caused by serious injury. Some people will get cataracts when they're younger due to risk factors like genetics, smoking, or diabetes. If untreated, cataracts will usually progress to blindness.

Cataract surgery improves vision in 9 out of 10 cases

Cataract surgery is considered very safe and effective. About 9 out of 10 people who get cataract surgery see better afterward, according to the National Eye Institute (NEI). Blurry vision after surgery is normal and should subside as the eye recovers.

People who have gotten cataract surgery typically report clearer vision. They may also experience brighter colors, as cataracts can tint your vision in shades of yellow or brown, according to NEI.

The effects of cataract surgery can also help pull people out of poverty, according to IAPB. The international agency says patients tend to report increased productivity and independence a year after cataract surgery.

Unfortunately, the cost of surgery can be too expensive for many people who suffer from full or partial blindness. A standard cataract surgery costs an average of $3,500 per eye, according to the nonprofit MyVision.org. Medicare and most private insurance plans will cover the cost of surgery and standard lenses, but some patients will pay extra to get prescription lenses.

In addition to footing the bill for 1,000 cataract surgeries over three weeks, MrBeast awarded some patients with financial aid for college, briefcases full of cash, and even a car.

There are 3 types of cataract surgery

Surgeons will use one of three common techniques to remove the lens in cataract surgery, according to IAPB. People with cataracts in both eyes will need two separate surgeries to restore their vision.

In the most traditional method, called extracapsular cataract extraction (ECCE), a surgeon uses a standard incision to remove the faulty lens and inserts a new, artificial lens. The incision must be closed with removable stitches, which means a longer recovery and greater risk of complications.

A more cutting-edge technique called phacoemulsification uses an ultrasound probe to break up the faulty lens before it is sucked out through a tiny incision. A foldable lens is inserted through that same incision without the need for stitches.

While the second procedure is preferred by those who can afford it, it is more costly and requires additional training and equipment. A third technique, called small incision cataract surgery, can provide a similarly fast and stitch-free recovery at a lower cost.

In MrBeast's video, he said the surgeon used a "tiny vacuum to suck up the clouded lens and replace it with an artificial one." However, he did not name the technique that was used.

Complications of cataract surgery may include swelling, bleeding, or infection; vision loss or double vision; unusual changes in eye pressure; retinal detachment; or secondary cataracts, according to IAPB.