This subject has zero to do with eye irritation.

The kids had to dive underwater and place their heads onto a panel. From there they could see a card displaying either vertical or horizontal lines. Once they had stared at the card, they came back to the surface to report which direction the lines travelled. Each time they dived down, the lines would get thinner, making the task harder. It turned out that the Moken children were able to see twice as well as European children who performed the same experiment at a later date.

With the exception, I suppose, that with eye irritation it would be more difficult to complete the tests in the first place.