A Blonde is having her eyes examined, when the Doctor points to a line on the eye chart, then asks the Blonde to recite the letters.

The Blonde states that she can't see that line.

The Doctor moves down a couple lines where the letters are larger, and asks the Blonde to recite them.

She can't

The Doctor is getting frustrated when he finally points to the huge E on the bottom of the chart. Can you read this, said the doctor?

The blonde responds: No.

The Doctor at wits end, decides to do something unconventional,
he opens the zipper of his trousers, and removes his manhood
and states, "Can you see this?"

The Blonde reply's, of course I can see that.

With that response, the Doctor informs his patient,
"You're Cock-eyed!"