It was usually done with simply bring a red-hot poker close to the eyes of the victim. The examples given above are from Western Europe and Byzantium. In the east it was a little different. Medieval Poland actually removed the eyes with pliers. Sometimes the eyelids were also removed. This was not necessarily a more or less brutal method than the red-hot method, but it was just as effective. (The illustration is of a Biblical story from a Byzantine manuscript.)
Bolesław's act outraged the population. Zbigniew had done nothing wrong in their eyes. It is thought that Archbishop Martin I of Gniezno excommunicated Bolesław, which meant not only was he unable to participate in the Sacraments, but his subjects' oaths of loyalty to him were void. A popular rebellion against the ruler was not unknown in Poland, so he had to take steps to regain his authority. That meant penance; serious penance.
Gallus Anonymus records that he fasted for 40 days and nights, and "slept in ashes and sackcloth, among the streams of tears and sobs, as he renounced communion and conversation with people." Gallus reports that Bolesław asked Zbigniew for forgiveness, and received it. That was not enough, however.
The duke then made pilgrimages to Hungary and the Abbeys of St. Giles (the Hermit) and St. Stephen I (first king of Hungary). He also went to do penance in Gniezno at the tomb of St. Adalbert of Prague, spreading gifts to poor people as well as clergy (probably including Archbishop Martin). Finally the excommunication was lifted.
I keep mentioning Gallus Anonymus; since I appreciate medieval historians, I'd like to talk more about what he provides the study of the history of Poland. See you tomorrow.
