A reminder of that very fine and beauteous film (2009) –

(if that doesn’t work, the trailer is at the official movie site, The Secret of Kells)

and thanks to our special foreign correspondent for pointing this gem out:

Paleontologist discovers 3-D secrets of Middle Age designs of Kells’ ‘angels’

OSFC adds:

mmm … you’d think that maybe Vikings and various chroniclers, church council attendees etc. should have noted that those weird irish monks not only had heretical views and the wrong hairdos but were also all cross-eyed …

To which a mutual friend (and fellow archaeologist) responds:

IF they ever saw THOSE monks.  🙂

We are all agreed: we want to see 3d experiments and special effects. Indeed, like in aforementioned film.
I reckon this might all explain the eccentric tonsures, too. C/o visual issues, misperception, others’ interpretation of resulting visible difference, and thence heresy and need to expunge. I’m a bit disappointed though, having always liked the idea of there being a vital ecological niche for the exceptionally myopic (and gingers, though hard to see how that could be tied in here).