Degree Thesis

Good afternoon,
my name is Laura and I'm an student of graphic design in Barcelona. For
my thesis I want to make an app and a web but I need some help because I
want to make it accessible for people with low vision. There are many
questions that I would like to ask you If you don't mind.
First of all, I wanted to ask about the icons. How should they be?

I will be really grateful if you can help me.

Thank you in advance,
Laura