There is a saying in Danyang: one of every two people on Earth who wears prescription glasses is looking through a lens made here. A county-level city of under a million in the Yangtze delta grinds roughly half the world's spectacle lenses — and the industry was planted, by accident, by city teenagers sent down to the countryside in the 1960s.
Danyang is a county-level city of fewer than a million people, sitting on the Yangtze in Jiangsu, twenty-five minutes by fast train from Nanjing. It grinds something like 400 million pairs of spectacle lenses a year — by the usual reckoning about half of all the lenses made on the planet, and roughly three-quarters of China's. More than 1,600 firms and 50,000-odd workers make it the world's largest lens-production base and Asia's biggest eyewear marketplace. The local boast is hard to disprove: of any two people on Earth wearing prescription glasses, the odds are even that one of them is seeing the world through a Danyang lens.
The origin is a piece of political history. In the 1960s, during the era when China sent its urban young people "down to the countryside," a group of educated youth who had worked in the optical factories of Shanghai and Suzhou were rusticated to the Danyang countryside, around Situ town. They brought a skill with them — grinding lenses — and set up small, makeshift workshops with a dozen workers, judging quality by eye. The campaign meant to scatter city teenagers into farm labour instead quietly planted a global optics industry in the fields of Jiangsu. The skill arrived with the sent-down youth, and it never left.
The cluster nearly died under the planned economy — by 1977 the workshops were collapsing — and was saved by reform. After 1978, freed to trade, Danyang's opticians started by selling glasses on the pavement in front of the railway station, then built a market: the Glasses City opened in 1986, and by the 1990s Danyang was the largest eyewear wholesale market in China. The pull was simple. Merchants found that Danyang lenses matched the big brands in quality at less than half the price, so buyers turned up with cash and ordered on the spot, wherever they found stock.
For decades the catch was the same one that traps every cheap-and-complete cluster: Danyang made superb lenses that nobody would pay much for. The brand belonged to Zeiss and the foreign names; the high-index resin raw materials and the coating machines that finish a lens were controlled from abroad. So Danyang ground the glass and took the thin end of the money. Breaking out meant breaking those monopolies — and it did: a local maker, Mingyue, cracked high-index resin materials with a Nanjing university in 2007 and dropped the cost to a third of imports, and in 2014 a Danyang firm built China's first home-grown lens-coating machine. The town stopped only grinding lenses and started owning how they are made.
Today a robotic arm holds a clear resin blank while cutting heads dance around it under a spray of water, and a custom lens emerges, ground to prescription, in about forty seconds. An order placed in a European optician's shop is transmitted to Danyang, made, and shipped inside a week; the town fills something like fifteen million custom international orders a year. It has even turned the trade into sightseeing — "eyewear tourism," a national scenic rating, the country's largest glasses museum. Set beside the other deep dives, Danyang is the cluster the Cultural Revolution planted by accident, that grew into the lens through which a good part of the world now looks.