It hasn’t been specifically studied in relation to Stargardt disease, but studies on blue light exposure in the general population show that it doesn’t affect vision. Stargardt is a genetic disease, so environmental factors have little impact, aside from a few things like overexposure to sunlight and vitamin A supplements.
It’s possible your vision is slightly worse due to the disease and your eyes are straining slightly to compensate. This then can cause headaches, blurred vision, and dry eyes. Continuing then to use the computer just makes the symptoms more apparent.
Make sure your office setup is ergonomically correct. Your screen shouldn’t be too close or too far, and you shouldn’t be looking up at it (which can dry out your eyes). Adjust the brightness and contrast to your personal preferences. Avoid placing your computer in front of a window. Take breaks and refocus your eyes every 20-30 minutes, and use hydrating eye drops. Blink frequently to keep your eyes from drying out.
Stargardt affects central vision, so looking at perfect shapes on a screen can make the effects more noticeable. I find that when I spend a weekend outside, my vision feels better just because I think about my eyes much less and nothing has actually changed