There is no standardized guidelines internationally in the usage of PPE among Ophthalmologist. How exactly it is spreading is still not known completely. The three doctors who died in Wuhan , were working in same unit including Dr Li Wenliang. It is believed that, they were treating asymptomatic glaucoma patients. Recent study found Viral RNA in tear film of conjunctivtis patients. Now ophthalmologist are preferring to use face shield along with N 95 mask, slit lamp breath shield to minimize droplet transmission and many more.
For more information: https://www.medscape.com