Right, I think it was Agent Foxtrot who mentioned the opposite. 
Here is a good website showing the basics of how to prepare and examine a blood smear. Colour me one of the people finding this a bit strange for a hobby - microscopes are a pain in the ass.
Since Leeuwenhoek invented the thing, they were mono until a few decades ago, and nobody went blind. 
I understand the advantage for long hours of work, but years ago i used a mono in the lab for many hours a day (old Bosch and Lomb) with no ill effects.
The mistake many make, whether using a microscope, telescope or a rifle, is to close one eye when using the other. Once you learn to keep both open, it does not tire out the other eye. However, whatever works.
Incidentally, with the digital camera, I spend most of my time observing the specimen on my computer monitor. Very easy that way to take photos.