V'einei Yisroel kavdu mizoken lo yichal lir'os vayageish osam eilav vayishak lahem vaychabeik lahem(48:10)
If Yaakov was blind how did he, in the very next possuk, say "to see your face I did not think, and behold Hashem showed me also your descendants."?
The Steipler Gaon Ztz"l had very week eyesight, he refused to wear glasses saying that he is better of this way, he will see less of what he shouldn't see. (When he was once trying to look at the Har Habayis in Yerushalayim he borrowed the glasses of an attendant. THAT he did want to see!)
May we suggest that Yaakov Avinu wasn't totally blind. His were weak from old age. He couldn't EASILY see. He was able to see somewhat, he was able to see that Menashe is to his right & Ephraim is at his left side. He must've. Otherwise from whence did he know to cross his arms?
Now the possuk can be read (misread maybe?) The eyes of Yaakov were weak from old age, they couldn't easily see, and Yaakov was very happy about that. This point (that his vision was weak) was dear to his heart. He loved it. He kissed it. He hugged it. Yaakov was thrilled that his sight weakened!