Can I go blind if the milky substance comes into contact with my eye?

The toxin in the white sap of the euphorbia is urushiol which is found in a number of related plant species including poison sumac, poison oak, poison ivy, and the Chinese lacquer tree. In Japan and some other Asian countries urushiol oil is used to produce darkly colored lacquerware. The toxin can be removed with soap and water within about 10 minutes. After that it seeps into the skin and scrubbing it off is fruitless. It will irritate the eyes, but I am pretty sure it will not cause blindness. I am not a medical doctor, so you should consult one to be sure. The eye will probably produce enough tears to wash it out. Immediately rinse the eye thoroughly with clean water.