Well, everyone is different.
First of all, make sure your sitting position, monitor/keyboard height etc is correct. Ergonomics are super, super important in computer usage.
Second of all, try using F.lux, it makes your computer easier on the eyes by adjusting the color temperature to match your room. It has dedicated settings for daylight and nighttime which you can tweak to your lighting.
Lastly, try using a tool that replaces your usual scrolling function, the way text on computers scrolls is really hard to follow while reading because your eyes are forced to readjust every time you move the page.
Personally what has really helped me in writing tasks in particular is to use two monitors, and treat them as physical workspaces- So if I have source material and a paper to write, I can keep one on my first monitor and the other on the second- This engages my sense of space somehow, because I find it a lot more natural to go between them, rather than suddenly having a new window in the same space the previous stuff was.
You can do that with a single monitor by resizing the windows to take up either the left/right or top/bottom half of your screen, though its a lot less effective unless you have an ultrawide screen. Default hotkey on windows is win + arrow for which edge you want it snapped to. Win + up and down maximize and hide the window, though, so vertical splits need to be done by hand.
Try magicscroll.net, it's a lot easier to get lost in books on your laptop with it because a). you don't have to touch anything, you can just read and the page changes as you read down and b). the colour themes are easy on the eyes. When I'm in my hammock and my arms are used to keep my laptop in place it's a godsend to have an ereader that changes page without touching it.
Also turn on f.lux to reduce eye strain.
I've made a lot of changes to the app. If you have a chance do you mind visiting www.magicscroll.net and letting me know how it works? Alice in Wonderland will be in your library as a test book.
Ok, I've made some significant changes. Do you mind letting me know if basic functionality is working and then I'll repost to the iPhone subreddit.
Links are at www.magicscroll.net and Alice In Wonderland
I have programmed, but not much of a programmer. A cbz is just a zip file. So all that is needed for a bare bones reader is to decompress the file, hold the images somewhere, and the view them sequentially. It is kinda like the same idea as http://www.magicscroll.net/ for ePub files. Which are also just zip files. The hard part is where to store the images when viewing.