Not medical advice. Progressive vision loss should be under the care of an optometrist or ophthalmologist. A low vision assessment is a distinct service from a routine eye exam, and it is the step that matches a person to the right magnification rather than the most magnification. Ask for it by name.
Start with the device in your pocket
Every current iPhone and most Android phones include a dedicated magnifier application, separate from the camera. It offers continuous zoom, a freeze frame so you can capture a label and then examine it steadily, a light, and a set of high-contrast filters that invert or recolour text. The filters matter more than the magnification for many conditions, because contrast sensitivity often degrades before acuity does.
On iPhone it is the Magnifier app, and it can be assigned to the accessibility shortcut so a triple-click of the side button opens it. On Android it is the Magnification accessibility feature plus the camera. Both are free and already paid for.
What the phone does well
Spot tasks. A price tag, a medication label, a restaurant menu, the serial number on the back of an appliance. Portable, always present, no extra thing to carry or charge.
What the phone does badly
Sustained reading. Holding a phone steady over a page for twenty minutes is a physical problem, not an optical one, and it is the reason people abandon the phone approach and buy hardware.
The cheap intermediate step nobody mentions
If the phone works optically but fails ergonomically, the missing piece is not a magnifier. It is a stand. An adjustable gooseneck or arm mount that holds the phone over the page converts the phone into a rudimentary desktop magnifier for a small fraction of the cost of one, and it is a genuinely good answer for reading mail at a kitchen table.
Test this before spending more. If a stand plus the phone solves the reading problem, the category is closed and you have saved a great deal of money.
When a dedicated magnifier is genuinely the right buy
Purpose-built devices earn their price on three things a phone cannot match.
Why we are not linking these to Amazon
Because you should not buy them there. Serious video magnifiers, the HumanWare Explore range, Eschenbach's devices, and desktop units such as the CloverBook line, are sold through specialist low vision dealers, and that is an advantage rather than an obstacle. The dealer demonstrates the device against your actual vision, which is the only meaningful test, and provides a repair path.
A magnifier bought unseen from a marketplace listing arrives matched to nobody's vision in particular, and the generic units that dominate those search results are largely interchangeable low-resolution screens on a plastic body.
The honest recommendation
A low vision assessment, then a dealer demonstration
In this one category the professional route is also the cheaper route, because it is the route with funding attached and the route that prevents buying the wrong magnification. Bring the actual material you want to read, your own mail and your own books, not the dealer's sample card.
An overhead phone stand and a good task lamp
Costs little, works this afternoon, and tells you a great deal about what you actually need. Lighting is the most underrated variable in low vision reading and the cheapest one to fix.