What is ironic about the condition in which Charlie finds his mother in Flowers for Algernon?

I would say the big irony about the visit that Charlie
makes to his mother lies in the way that, to a certain extent, their conditions and
roles have been reversed. Now, instead of Charlie's mother having to look after her son,
it is Charlie who is intelligent and having to look after his mother. She shows that she
is losing track of reality, and at one stage, after having recognised Charlie, suddenly
thinks he is in her house to ask about the electric bill. However, the biggest irony
comes when Charlie asks her about her children, and she tells Charlie (who she does not
recognise to be her son at this stage) about her son:

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"I had a boy. So brilliant that all the other
mothers were jealous of him. And they put the evil eye on him. They called it the IQ but
it was the evil IQ. He would have been a great man, if not for that. He was really very
bright--exceptional, they said. He could have been a
genius..."

The irony of this
conversation is of course that, in spite of his mother's dreams of Charlie and the way
that she obviously ignores reality, Charlie's mother is right: her son has become a
genius and has shown himself to be truly exceptional, thanks to the operation that has
become both a blessing and a curse to Charlie.