You wouldn't die "of myopia", you would die because myopia means you didn't see things that might be hazardous.

I’m sorry you’re missing my point. If a culture grows up eating a lot of long chain poly unsaturated fatty acids, and then suddenly they stop, then the myopia develops.

In populations that depend on a very heavy vegetarian diet, which is comprise primarily of shortchange, polyunsaturated fatty acids, they might have other issues not related to myopia when they go off of their traditional diet.

Myopia in my opinion is a result of the industrialization of food.