All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
The preponderant opinion among the scholars is that blindness in Chapter Taha [Quran 20:124] means being unable to see, lacking the sense of sight.
A non-Muslim will be resurrected on the Day of Judgment blind, not being able to see anything.
This opinion is the preponderant one for the two following reasons:
1- The non-Muslim says: {While I had sight before.} [Quran 20:125]. This means that it is the blindness which is the opposite of sight.
2- Allah Says in another verse that the non-Muslims will be resurrected while having no senses; Allah Says (what means): {And We shall gather them together on the Day of Resurrection on their faces, blind, dumb and deaf.} [Quran 17:97].
However, some scholars are of the view that what is meant by blindness here is the lack of insight and not the physical blindness. So, the blindness of the sight is the inability of giving sound argument or proof that could help them on that Day. They base their opinion on the following verse. Allah Says (what means): {Verily, it is not the eyes that grow blind but it is the hearts which are in the breasts that grow blind.} [Quran 22:46] Nonetheless, the use of blindness in the second instance is metaphorical and there is no evidence to understand this meaning, so the first opinion is the preponderant one.
Allah knows best.