وَبَيْعُ الْأَعْمَى وَشِرَاؤُهُ جَائِزٌ، وَلَهُ الْخِيَارُ إِذَا اشْتَرَى
Translation: A blind person’s buying and selling are valid, and when acting as purchaser the blind person has an option.
Blindness does not remove contractual capacity: a blind person may lawfully buy and sell.
When that person is a purchaser, the text recognizes a choice and then specifies functional substitutes for ordinary sight: touch, smell and taste, depending on the goods.
Do not turn the statement into “every blind seller always has the option.” The text specifically says when purchasing.