Caligo

·noun Dimness or obscurity of sight, dependent upon a speck on the cornea; also, the speck itself.

caligo
cālīgo (call-), ĭnis, f. [root cal-, cover; cf.: oc-culo, clam, cella], I a thick atmosphere , a ...

A New Latin Dictionary by Charlton T. Lewis Ph.D. and Charles Short, LL. D.
caligo
cālīgō (1) inis, f 2 CAL-, a thick air, mist, vapor, fog : picea, V.: atra, V.: noctem eadem calig...

An Elementary Latin Dictionary