When Saul meets the resurrected Jesus on the road to Damascus, he is struck blind (9:8). While this blindness might be explained as the result of the theophany (he looked into a bright light and was physically damaged as a result, Acts 22:11 more or less implied this). But it is likely the original readers of the book of Acts would have thought this blindness was a judgment.
Perhaps the blindness is the result of the revelation Saul received. At the very least he learned Jesus is the messiah and he really was raised from the dead. As a teacher trained in reading the Hebrew Bible, Saul would have interpreted the glorious light he saw as a theophany. This would immediately associate Jesus with God in some very real way. This revelation alone would have been shocking to Saul, but if more revelation than this was given, then Saul experiences an encounter on a par with Moses at the burning bush in Exodus 3.
Luke may intentionally contrast two blind men in the middle of the book of Acts. In Acts 9, Paul was persecuting the church and he is temporarily struck blind. Over three days he comes to fully realize what God has done through Jesus and he is called to be the “light to the Gentiles.” When the three days are over he is free from his blindness, but in a sense he had been blind all along as he attacked those who were claiming Jesus was the messiah.
In chapter 13 Luke introduces another Jew who seeks to hinder the preaching of the Gospel, Elymas. I plan on returning to this story later, but notice how this man is blinded and has to be led away by the hand, very similar to Saul in Acts 9. The difference is Elymas does not recover, as far as we know, and become a believer. He remains in his blind state, unable to see the truth of the Gospel.
Spiritual blindness is a well-known theme from the Hebrew Bible. In fact, Isaiah 6:9-10 is the most important context for spiritual blindness since Isaiah describes the inability of Judah to respond properly to God in the eighth century B.C. While there is a remnant of believers, the nation as a whole will reject the preaching of Isaiah. Jesus applies this verse in a very similar way to Pharisees in Matthew 13 as an explanation for teaching in parables, and later Paul will quote the verse and apply it a third time to the Jewish rejection of the gospel (Acts 28:25-28).
Saul was spiritually blind when he “saw the light” on the road to Damascus. Being healed from his physical blindness highlights his spiritual awakening. For the first time, Saul sees Jesus for what he really is, and his spiritual blindness is healed.