(CNN) Doctors treating a Taiwanese woman for a swollen eye were shocked to find four tiny bees living under her left eyelid.

The miniscule insects, known as sweat bees, are 3 to 4 millimeters (0.12-0.16 inches) in length, according to CNN affiliate CTS.

"I saw something that looked like insect legs, so I pulled them out under a microscope slowly, and one at a time without damaging things inside," Hung Chi-ting, the head of the ophthalmology department at Taiwan's Fooyin University Hospital, told reporters at a news conference.

Sweat bees, also known as halictidae, "nest near graves and in fallen trees, so it's easy to come across them while hiking in mountains," Hung explained.

According to CTS, the woman, identified by her family name of He, said she thinks the insects blew into her eye at a relative's grave site when she visited it with her family. She washed her eyes with water but kept experiencing severe pain.

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