I dont know of any software but there are glasses, contact lenses, and magnifying glasses.
The person you are giving this advice to knows that there are glasses, contact lenses and magnifying glasses. His or her eyesight is impaired so he or she will already have glasses but still finds it difficult to see the computer. I have poor eyesight myself and it is a real struggle to see to read a book etc. My optician has given me the strongest glasses they can and I have been to see eye specialists but there is nothing they can do for me as it is the optic nerve that is the problem in my case. It is damaged and there is no way of repairing it. I set my resolution very low so that it is as big as I can make it but I still struggle to see and it will only deteriorate as I get older. People who have good eyesight do not understand what it is like. There is no easy answer.
There are virtual magnifying glasses you can download. The one I use iscalled Virtual Magnifying Glass and it is very good. You can change your resolution by right clicking on your desktop space and selecting properties and settings and slide the screen resolution bar over to the left which makes most things larger. When you are viewing an internet page you can go into view at the top of the page and click text size, largest that is if you are using Internet Explorer. If you are using Google Chrome click the spanner at the top right of the screen and click zoom until you can see better.