Optics of low-vision magnifiers

6 June 2017
Volume 18, Issue 2

This article discusses the determination of magnification needs for reading in low vision patients.


Magnifiers are commonly prescribed for low-vision patients. This article discusses the determination of magnification needs for reading, it warns against relying on the labelled magnification and it advocates using equivalent viewing distance (EVD) to quantify magnification effects. Spectacle magnifiers, hand-held magnifiers, stand magnifiers, telescope systems and electronic magnifiers are discussed. The most important optical parameters are identified and methods are given for determining the EVD and the field of view these magnifiers provide. There are simple methods for determining equivalent powers of lenses and the image locations and enlargement ratios of stand magnifiers.

Sign in to continue

Forgotten password?

Sign in to view the article

Not a member? Start enjoying the benefits of College membership today. Take a look at what the College can offer you and view our membership categories and rates.

Related further reading

New research has found links between the severity of visual impairment and the risk of dementia. Kathy Oxtoby asks: how can optometrists play a greater role in supporting patients with these conditions?

Natalie Healey explores how optometrists can support the diagnosis and management of cerebral visual impairment.

A glance at what’s happening in the world of technology.