2 Peter 1:9

On the other hand their absence makes a man spiritually blind, or at least short-sighted.

μυωπάζων (the more natural form of the word would have been μυωπιάζων, cf. μυωπία) means screwing up the eyes in order to see, as a short-sighted man does. It limits the word τυφλός, and does not emphasize it.

λήθην λαβών, etc. He forgets the cleansing of his former sins, which took place when he was baptized. A phrase in Hebrews 1:3 combines two of the words used here “διʼ ἑαυτοῦ καθαρισμὸν ποιησάμενος τῶν ἁμαρτιῶν ἡμῶν.” Among other passages quoted by Mayor, one from 1 Corinthians 6:11 is specially apt: καὶ ταῦτά τινες ἦτε�, ἀλλὰ ἡγιάσθητε. The man’s forgetfulness of the cleansing he received in baptism paralyses his efforts to put away evil habits.