I find it really cool that often things are invented by two different people at the same time. It makes me wonder about how inevitable inventions really are. How often is it really a great leap of logic and how often just the logical next step when all the ingredients are already present?
I'm sure for the ophthalmoscope, you need things like precision metal and glass making and knowledge of how the eye works and so forth.
Was it inevitable that it should look the way it does and work the way it does? Or just a coincidence that two people came up with it at the same time?
Of course, we'll never know for sure, but it's interesting to speculate.