Now, there are some dictionaries that list the Latin-style plural. The American Heritage Medical Dictionary is one, but even it lists both the English-standard “scleras” along with “sclerae”. And there’s a wonderful tool that can show that this is probably the right way to go, if you’re going to create a descriptivist dictionary.

scleras vs. sclerae Ngram

Google’s Ngram Viewer lets you see how different alternatives have been used in actual publication throughout the years. And, except for a period in the 1860s, “sclerae” definitely outpaces “scleras” in English publications. So I won’t say either is wrong.

I will continue to use the less-common “scleras”, though. English has enough inconsistency that I see no reason to use non-standard plurals when standard plurals are accepted. I don’t say “alumnuses”, for example, as it has barely-there use—but in that case, I’d probably opt for the less formal “alums” rather than “alumni”, if the outlet permitted the drop in formality. But I opt for “vertexes”, “cherubs”, “dogmas”, and “ninjas” over “vertices”, “cherubim”, “dogmata”, or “ninja”; both forms are in measurable use, so why not adopt the word fully into English?

—jhunterj