This is a very good episode where we see Fonzie's vanity in spades when he finds that he is having trouble seeing properly. Not wanting anyone to know this, he continues along as before until he can't avoid the inevitable anymore, he will need to see an eye doctor!
Enter Mickey Malph, (yes, really!) Ralph's father, who is a highly successful optometrist. Very reluctantly, Fonzie goes to see him and finds him just as annoying as his son (and just as prone to not funny practical jokes.) All jokes aside though, Mr. Malph informs Fonzie that he needs to wear glasses. Naturally, Fonzie is far from keen on this idea and resists putting them on as often as possible until finally, he realises that wearing them is not only necessary, but it might also actually be cool!
Lots of laughs in this episode if you exclude all the un-funny lines by Ralph's dad.