Eye size, flight speed and Leuckart's Law in birds

Hall & Heesy (2011) Eye size, flight speed and Leuckart's Law in birds, J. Zool., 283, pp. 291-297.

I just skimmed the abstract.
There written there was no relation between the eye sizes of birds and their flight speeds.
I wonder what about acceleration then.
Falcons must be more agile than swans and having larger eyeballs? No relation?