Visually Impaired - Changing Gamma allowed?

I'm a bit visually impaired and even at full brightness, I can't see anything in some of the beginning areas, especially the sewer dungeon. I had to turn off my room lights and close all the windows to even see the blocks in front of me. Can I change the gamma in my options.txt, or is that against the rules for modification of game files?

TL;DR: can't see even in lightly obscured areas, can I change gamma in game files to accommodate?

 

Full bright is allowed so I imagine gamma is allowed

 

decrepit sewers lighting is bs, i've seen new players try to run it on normal gamma and it's actually unplayable