Watch Christian Guardino Sing John Lennon's 'Imagine' on 'American Idol' and Bring Katy Perry to Tears

On Sunday's episode of American Idol, the contestant delivered a soulful take on the late former Beatles member's signature 1971 hit, garnering emotional responses from all three judges

American Idol contestant Christian Guardino left judge Katy Perry teary-eyed with his powerful performance of a John Lennon classic.

On Sunday's episode of the iconic singing competition series, the 22-year-old aspiring musician delivered a soulful take on the late former Beatles member's signature 1971 hit "Imagine," garnering emotional responses from all three judges — specifically Perry, 37, who was reaching for tissues midway through the performance.

Wearing an all-black outfit complete with a bomber jacket and fedora, Guardino belted out the Yoko Ono co-written track's peace-calling lyrics, accompanied by a pianist. "Imagine there's no heaven / It's easy if you try / No hell below us / Above us only sky," sang the top 20 contestant, who slipped into an impressive falsetto voice following the line, "Imagine all the people / Living life in peace."

Throughout his performance, Perry was seen dabbing tears away from her eyes with tissues before getting out of her chair with fellow judges Lionel Richie and Luke Bryan at the end to give Guardino a standing ovation. "Katy, how many stages of 'cry' are there? Because Katy has went through all the consonants of crying," said Bryan, 45, after the contestant finished singing. "Oh my goodness. [Christian,] you just slayed that performance. I didn't hear anything but perfection."

Christian Guardino. ABC

Richie expressed an equally positive sentiment in his comments for Guardino. "You are the poster child for the power of the human spirit," said the 72-year-old "Hello" musician. "There are so many people in the world who would say 'This is what's wrong with my life,' and then you walk out and say, 'Let me tell you what's next,' and you've taken all of your blessings and joined us on this stage. We love what you're doing."

Having stopped crying and dried her eyes, Perry then told Guardino she was especially impressed with his talent and composure given his backstory, as the contestant had previously gone blind due to a rare condition before undergoing experimental surgery at 13 years old and regaining his vision.

"Hearing what you have overcome and the mountains you've climbed and the attitude of gratitude that you have, and then you sing 'Imagine,' which is a world-changing song…you were put on this planet to do something super powerful and you are doing it right now and in this room," the "Never Really Over" singer said. "God bless you, Christian."

Earlier this month, Guardino spoke to the New York Post about the "rare disorder" that caused his blindness and how doctors were able to reverse it through surgery. "I was born with a rare disorder called Leber congenital amaurosis, but we call it LCA," he told the outlet. "It's a disorder that causes a gene that's missing in your eye, because if the gene isn't there, it's not producing proteins that your cells need to live, so they all start to die off and then it causes inevitable blindness."

"But when I was 13 years old, I received an experimental gene therapy and a few years ago, it got approved by the FDA," continued Guardino. "And when I got the treatment, it was experimental and it was in hopes just to stop that inevitable blindness, but for me, it's done so much more. I got to see the moon for the first time. I got to see stars for the first time, fireworks."

Prior to his time on American Idol, Guardino appeared on America's Got Talent at 16 years old in 2017 and sang a cover of The Jackson 5's "Who's Lovin You" to positive reception from notoriously tough judge Simon Cowell. "You are one of my favorite contestants I've seen this year. Not only in terms of your voice. I just like you," he told the then-teenager, who teared up onstage. "There's something about you, and it's just the best possible feeling when we meet someone like you."