This site is in the middle of a major expansion. It was originally designed as a resource for vision professionals who wanted to better understand how to care for patients with vision impairments. I'm now reworking the site with content for the general public — people with low vision and people who want to know more about low vision. Once that section is complete, I'll rework the section for vision professionals to better integrate with the general public section. Keep checking back to see how it's going, and if you find the content helpful please consider contributing to support the effort.



There’s a trade-off between magnification and issues like field of view and image stability. Get the illumination right first, so you don’t need to use so much magnification.

Whenever we magnify a document, it gets bigger.

Sure, that’s a “Well duh” moment, but let’s look into the implications of that a bit deeper.

Let’s say we’re magnifying an A4 page (American readers, that’s our standard letter-size page) by 6x. How big is the image of that page? Suddenly we’re dealing with a page image which is around six feet tall by four feet wide. And we’re looking at it through an aperture which is, what, not much more than five centimetres across, depending on which model you use.

Immediately that means you’re only seeing a small portion of the page in one go, so you now need to move the magnifier around the page to see all the content. And it gets worse as we use stronger magnifiers — the image gets bigger and bigger, but the aperture gets smaller and smaller. Having only a small field of view can greatly limit potential reading fluency.


Aside: You can see more by bringing your eye closer to the magnifier lens. I’ve heard it said that you can tell where the low vision room is just by listening out for the voice repeating “Hold it closer to your eye. Make sure you hold it closer.” I describe this technique to patients as the ‘Porthole Principle’ — if you’re in a ship and you want to see more of the view, you need to move closer to the porthole.

Even with that very close eye position, with the stronger powers (10x or so) the field of view is still very limited, only two or three words. Imagine taking a piece of cardboard with a hole about the size of a small coin and viewing your book with the card flat on the page. How quickly could you (with normal vision) read while having to move that small aperture around on the page? Better yet, try reading a full page or so using an actual 10x magnifier and see how you go.


Another limiting factor is image flow. As you move your magnifier from one side of the page to the other, you only move the physical magnifier by the width of the page. But the image of the page is six times wider, which means as you move the magnifier from left to right the magnified text rushes back the other way six times as fast. If you’ve ever tried to read a billboard as your train is moving through a station, you’ll understand how uncomfortable that can be. Our saccades get all mucked up.

Comment: With practise you can learn to move the magnifier along in precise little jumps, then each time refixating and reading a small snippet of stationary text, but it’s still not as fast as simply saccading along a full line.


The magnifier has to be kept at the right distance from the page, otherwise the print goes out of focus, which gets more and more difficult to manage as the magnifier gets stronger. And if you have any sort of hand tremor (and many of our elderly patients do), with our 6x magnifier the image will shake by six times as much — we make the print bigger, but induce a nystagmus (yay us).

Aside: This is where stand magnifiers help keep the image steady. Which is great, but they have their own difficulties — especially when trying to use them to read books, in which the pages don’t sit completely flat, and the edge of the stand makes it hard to see into the edges of the page near the spine of the book.


And then there’s the simple fact that most magnifiers need a spare hand to hold them, which leaves only one to hold the book or newspaper. That’s not easy, especially if it’s a big book, or if it’s floppy like a newspaper. And many of our older patients simply don’t have the arm/hand strength to hold a book one-handed. Reading stands can help, but even then it can be a serious back/neck strain to keep the eye close to the magnifier and the magnifier close to the page.


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