Attendees of a Yuga Labs’ ApeFest event on Nov. 4 in Hong Kong have reported burns, damaged vision and “extreme pain” in their eyes, which they attribute to the use of improper lighting.

“Woke up in the middle of the night after ApeFest with so much pain in my eyes that I had to go to the hospital,” wrote one attendee, CryptoJune, in a Nov. 5 X (Twitter) post.

“Doctor told me it was due to the UV from stage lights," they added. "I go to festivals often but have never experienced this. I try to understand how it could happen… it seems like the lamps [were] not safe."

One attendee noted many of those reporting eye problems were those “up close” to the lighting display on the event's main stage.

Another ApeFest guest, who goes by the pseudonym Feld on X, described identical symptoms.

“Anyone else’s eyes burning from last night? Woke up at 3am with extreme pain and ended up in the ER.”

Of the hundreds of ApeFest attendees, at least 15 reports of vision damage have appeared on social media, suggesting the concerns were limited to guests who were in close proximity to the stage lighting.

Yuga Labs but did not immediately respond to a request for comment.

Hong Kong partygoers have experienced medical issues following exposure to improper UV lighting at an event before.

On Oct. 20, 2017 a number of attendees at a party thrown by streetwear brand HypeBeast reported painful burns and eye damage.

It was revealed by the events’ DJ on Oct. 26 that the contractor tasked with setting up lighting at the party had used a series of Philips TUV 30W G30 T8 light bulbs — which according to Philip’s website — emit 12 watts of UV-C radiation, mainly used for disinfecting surfaces.

The reports of vision damage in both cases line up with a condition called photokeratitis, also known as “Welder’s eye.” The condition is caused by prolonged exposure to extreme levels of UV radiation, typically from artificial sources such as welding lamps but can also come from natural sunlight reflecting off bright surfaces such as snow, more commonly known as snow blindness.