Contrast setting is maybe the most important setting you want to spend time on to improve reading on your screens.
First, let's talk about contrast setting on TV and stand alone computer screens. We are talking about the contrast option usually buried in the settings options of these type of screens. If you struggle trying to find that option or if you didn't know it existed, you are not missing much. Even with a good eyesight it's almost impossible to make a difference between a low or high contrast on these screens.
You will always have better results using the contrast option from the computer attached to these screens. For example, Mac computers can increase contrast to such an extent that each word starts to bleed light at its highest contrast setting.
When you deal with a device with its own screen, chances are the software running your device is optimized for your screen. Head directly to contrast settings and play around to see what works best for you. This works for phones and laptops.
Once you are done with contrast settings, there are other options that are not directly related to contrast but work the same way. For example, eliminating transparency usually increases contrast dramatically. Try this on Apple TV for example, it's the most dramatic way to improve screen readability.
Increase font size or use bold font works as well.
Android devices allow you to change font type across the device, some fonts are easier to read than others. Experiment with a few to see what works for you.
Some devices offer you an option for people with light sensitivity, Apple TV for example. Selecting that option darkens the screen. It doesn't work well for my condition but you should try on your own to see if it works well for you.
There is no single magic setting that will work for everyone, unfortunately; you are likely to spend some time fine tuning these settings. Remember that if you are sharing a screen with someone with different eye conditions those settings may not work for them. If your system allows you to save your settings, take advantage of it. At the very least take note of the changes you made. That way, you won't have to spend too much time resetting your screen after your friend or family member changes them to their preferences.