The older we get, the more our vision degenerates in one way or the other therefore some degree of low vision is definitely inevitable. The reason why a lot of older people usually get low vision is that aging leads to a slow degeneration of light-sensitive cells found in your retina, which happens to be where vision processing occurs.
When you start experiencing vision loss in the central part of your retina called macula, magnification is usually what is needed. This area is the one capable of reading small letters. A magnifiers comes in to assist you compensate for a damaged macula by using more of the healthy retina surrounding the damaged area to create visual images.
Eye injuries can also have permanent damage to the structures of the eye necessary for sharp vision. Advanced macular degeneration can create a blind spot in central vision meaning that you can be able to view better using the edges of your sight but you would have to use a magnifying device to assist you see. An electronic magnifier magnification can be adjusted to give you such magnification.
Vision problems can also be caused by eye problems that are not detected by simply testing using a standard eye chart. What this means is that it can be very hard for you to view objects against backgrounds that are of the same colours, hence loss of contrast sensitivity. You might also develop a colour vision deficiency or a loss of night vision.
People usually have blind spots in different parts of their visual field hence the reason why optimal magnifier is different for different people. Therefore people have to choose the deice that suits their goals and needs. Also you need to address lighting and try out different colour displays on video magnifiers.