Why is Wei Zi blind?

In the process of escape, Swallow and others were attacked by a group of men in black. The swallow was captured and the golden lock accidentally fell off the cliff. Wei Zi fell to the ground because the carriage was out of control. After a chaotic fight, Erkang and others were forced to disperse. Erkang stayed at the inn with the injured Wei Zi, Yongqi and Xiao Jian waited for an opportunity to save the swallow, but the golden lock fell off the cliff and was protected by Liu Qing and Liu Hong. The fact that Wei Zi was blind dealt a great blow to Erkang and Wei Zi.