There are two types of optical aids – the simplest is by using a magnifying glass through which one sees a magnified text. Another principle is to assist the eye to see at shorter distances which gives relative distance magnification. In this case we generally talk about loupes, high-powered lenses which allow clear vision at close distances.
With central field loss or reduced acuity the general rule is that magnification should allow, at least, text of 6/12 (0.5 or 20/40) to be read. This means that with a visual acuity of 6/60 (0.1 or 20/200) that 5x magnification will be required. A visual acuity of 6/120 (0.05 or 20/400) will require 10x magnification and so on. Magnification of 10x requires a +40 diopter loupe which will give a reading distance of 2.5 cm.
It is easy to determine what magnification you need by reading the text Come Closer – backwards.
When you need high magnification a video-magnifying system, which can give magnification of up to 50-60x, can be an alternative. It allows you to see at a normal distance but at the same time will limit the number of letters that are visible at one time during fixation. For an introduction to “using a video magnifier” follow the link below.
Use a monocular telescope and find your BRA(Best Retina Area) for distance. Another alternative is to use the camera of your smartphone – take a photo and then use the zoom function to magnify the image.
Read the chapter about magnification from the book, ”Looking Forward” by Krister Inde.
Read about training Eccentric fixation in the book ”Looking Forward” by Krister Inde.