Isaiah 6:9-10
" 'Be ever hearing, but never understanding;
be ever seeing, but never perceiving.'
10 Make the heart of this people calloused;
make their ears dull
and close their eyes.
Otherwise they might see with their eyes,
hear with their ears,
understand with their hearts,
and turn and be healed."
A major theme throughout Isaiah is how the great plan of God will not even be believed by people, they are blinded and confused.
The Bible verse you used is out of context.
Isaiah 29:9-12
9 Be stunned and amazed,
blind yourselves and be sightless;
be drunk, but not from wine,
stagger, but not from beer.
10 The LORD has brought over you a deep sleep:
He has sealed your eyes (the prophets);
he has covered your heads (the seers).
11 For you this whole vision is nothing but words sealed in a scroll. And if you give the scroll to someone who can read, and say to him, "Read this, please," he will answer, "I can't; it is sealed." 12 Or if you give the scroll to someone who cannot read, and say, "Read this, please," he will answer, "I don't know how to read."
This is about misguided prophets and seers that cannot read and understand the Word. Because of their ignorance they cannot see what is sealed in the Word, the prophecies for Jesus Christ.