Take a look at the sentence again:
Because his glasses were so thick, Quincy refused to get
contacts, he worried that equally thick
contact lenses would make him look like a bug-eyed space alien.
For a sentence to be fused, you must have two complete sentences run together with no punctuation. In the example above, a comma joins the two sentences. Because his glasses were so thick, Quincy refused to get contacts is one sentence. He worried … starts the second sentence. Thus, the error is a comma splice.
Remember that both comma splices and fused sentences are major errors. They make your reader think that you cannot write a correct sentence. Because the sentence is the most basic building block of a piece of writing, comma splices and fused sentences make you look like an amateur!
To fix the problem above, you could put a period after contacts and begin he with a capital H.