Convert from exameter to gnat's eye

Unit Definition (exameter)
An exametre (American spelling: exameter, symbol: Em) is a unit of length equal to 1018 metres.

Unit Definition (gnat's eye)
The gnat's eye is an idiomatic "unit" of distance; it's common to hear that something is "as small as a gnat's eye". In fact, the eyes of typical gnats tend to have diameters similar in size to a hair's breadth: roughly 100-150 micrometers (0.10-0.15 millimeters).