Most magnifiers are bi-convex (such as handheld magnifier , loupe , pendant magnifier , pocket magnifier , keychain magnifier , etc.) or plano-convex (bar magnifier an dome magnifier ). But, reading glasses are positive meniscus.

As a magnifying glass for reading generally does not need high magnification power, the lens will be relatively large. So, you can have a larger field of view to facilitate reading. Nowadays, some of them are even designed to be rectangular to enlarge field of view, and with LED bulbs (LED magnifier , lighted magnifier , or illuminated magnifying glass ) so that people can still read in dark environment. Reading glasses are to be wore on the face and the field of view are 2 small circles, and it only works in bright environment.

Significantly reduced lens thickness results in a substantial savings in material cost. Fresnel lenses can reduce weight, which reduces mounting and assembly cost. Extremely giant Fresnel lens up to 1000mm can be used to replace a very expensive conventional mirror assemblies in large optical systems.

Magnifiers are mainly magnifying objects to let people see things and small fonts clearer, not an ideal alternative for vision correction. Normal people can see tiny things through pocket magnifier , keychain magnifier , pendant magnifier or card sized Fresnel lens . However, you need to examine your eye by an optometrist before wearing reading glasses since individual eye diopter is different. So, image of the object will properly fall on retina to reach the intention of seeing things clearly.

Magnifiers and reading glasses belong to convex Lens. If convert common magnifier to reading glasses, it is equivalent of 1000 - 2000 degrees (equal to 100 times of reciprocal focal length). Obviously, it's not suitable for individuals. Replacing reading glasses by magnifiers in long-term will cause eye soreness, swelling, and headache. The most serious effect is causing damages to your eyes. So, you must examine your eyes by a professional optometrist prior to wear reading glasses. You cannot wear it at will. Magnifiers are suitable for short-time use and for some special occasions.