All I can find is that it was a "defect" from birth:
"Hemingway's left eye was defective from birth, not from boxing with his son Jack."
It prevented him from joining the army:
"In May of 1918, Hemingway wanted to join the Army but could not due to a defective left eye which he inherited from his mother. "
Could you supply the source for your answer? Hemingway's eye problem was from birth, but:
"Ernest Hemingway, his brother and his father all had at least two things in common, Hilary Hemingway said.
Each developed diabetes late in life, and later committed suicide. It's only been in recent years that medical science has discovered the strong links between diabetes and depression, she said, adding that she hoped the result would be a new understanding of what some have called "the Hemingway curse."
I'd be very interested (and surprised) to discover that
Hemingway had the eye disease you say he did.
Would you be so kind as to copy and paste the web site address?