How do you spell ophthalmology?

Putting on my coat 45 minutes before my doctor's appointment, I said to another regular at the coffee shop, "Do you know how to spell "ophthalmology?" He hesitated a moment, then said, "Well, I'm not a very good speller, but I do know that one. O-p-t-h-a-l-m," and then he hesitated, "then it's either an "a" or an "o". "You were in trouble on the first syllable," I said. And I spelled it. "Think of 'my eyes are off, so I'm going to the ophthalmologist.'" This phth is actually pronounced as p-th, and is called a medial cluster. It doesn't appear in many English words, which is probably why it is so often misspelled. Diphtheria isn't very common anymore, thank goodness; Ben Franklin tried to rid our language of diphthongs, and who uses naphtha soap anymore? So other than having an appointment with an ophthalmologist, you have little use for the medial cluster.