Hi I just finished my first play though of Pathologic, as the Bachelor, and I enjoyed it greatly. I will perhaps write a more detailed analysis later but for now I have a question. What is the Bachelor's vision thingee and what is it used for? I couldn't find anything in the manual about it and was curious.

It highlights infection clouds in red, even before they appear. Lenses increase the duration

This device can be used to see the clouds of infection from distance. There are two types of them on the street, as you may have already noticed. Those static ones, mainly waiting for you on the roads, and those moving that "attack" when notice you. The more lenses you have used to improve the vision device, the farther you can see. If I am not mistaken, without these lenses you basically see only the clouds that you see with your own eyes... or it's just the device is very short-ranged. However, it defeinitely becomes much better with several of them used. You start to see then invisible moving clouds, slowly floating pretty far away.

Gee, that might have come in handy then!

For anyone else reading this:
The vision thing is really useful. If you're playing as the Bachelor, press 'v' (default) to use it. When you complete certain quests, you will be given new lenses. Just 'use' them at any point and they'll upgrade the device.

P.S. I'd like to know what this mysterious scientific marvel looks like. I'm guessing it's an ornate and complicated steampunk-style monocle

To be honest I found it pretty easy going, after about Day 5 or so, even without the vision thingee! I had tons of money and drugs and had gotten quite used to walking in a particular way when going into infected areas. However before I play as the other characters, who I hear are much harder, do they have any special items like this one that I should be aware of?

When you're playing as Burakh, you'll learn about picking herbs and mixing them together to make healing concoctions. But it's all explained at the right point during the story. The Bachelor is the only character with an easily-missable keypress, I believe.

I never knew about the vision thingy until about the seventh day when I activated it by accident. Whenever I'd receive a lens, I'd click on it and think that whatever it was I had just discarded by accident. Could never figure that out. Hehe.

I noticed it when configuring the keys (I'm left handed and have to change the setting in every game except point&click), but since the german version mistranslated it as a telescope (the one that is mounted on a rifle), I couldn't figure out how to use it properly...

I completely wasted the vision thingee myself. I checked the keys when I started the game, and noticed it was there, but I didn't know what it did, and it was never really addressed in the game, so I just ignored it. I, too, had no idea what the lenses were supposed to do (I thought they must have had something to do with using the microscope...). Oops. Ah well, I pretty much had the locations of the infection clouds memorized before too long, anyway!