Magnification: Telescopes and Magnifiers
The most simple form of magnification for children is provided by reducing the viewing distance of the material being read, both for near or distance – that is to move in closer to the material being inspected. A shorter working distance may have the same effect as using a magnifier, for example, watching the television with a 2x distance magnifier will be the same as halving the viewing distance.
Young children, except those who are aphakic (without a lens), are able to focus at a working distance of 10cm for a short time. Viewing an object close to their eyes may offer sufficient magnification for some tasks. A short working distance, with or without reading glasses, provides the greatest field of view.
Telescopes e.g. monocular – for distance viewing
Distance vision devices are useful for viewing the whiteboard, watching sporting events, checking bus destinations etc.
Distance viewing can be provided with either a monocular or binoculars, however both reduce the visual field to around 10 degrees. Typically 4x, 6x, or 8x magnification is available – generally the larger the magnification, the smaller the field of view.
Magnifiers – for near viewing
Magnifiers, also known as “low vision devices” or “optical aids”, can be used to augment residual vision. Simple hand-held, bar, stand or spectacle mounted magnifiers can provide enlargement for near vision tasks such as reading a novel, studying a map, or viewing a price in a shop etc. Hand-held magnifiers are often smaller and more portable. Stand magnifiers may be a better option for prolonged tasks, as a suitable working distance is maintained. They can also be useful as a means of keeping the place when working from a textbook to a workbook.
Magnifiers vary considerably in strength of magnification, field of view, working distance, size and portability, price and additional characteristics (e.g. inbuilt lighting). Up to 20x magnification is common in optical aids.
Higher magnification can be achieved with electronic magnification units. Hand-held and pocket units consist of an inbuilt television camera, light source and screen – these may offer better access, but are also bulkier and more expensive.
Sources of telescopes and magnifiers
In Victoria, magnifiers can be trialed and/or purchased at:
East Melbourne Optometry and Low Vision Centre
Optometrist Alan Johnston – for people with moderate to severe vision impairments
Suite 214, 100 Victoria Parade East Melbourne
Tel (03) 9654 1331
Educational Access Technology Expo – conducted at the Statewide Vision Resource Centre annually – see the PD Calendar for information
Tel: 1800 756 849
3 Chesterville Rd Cheltenham Victoria 3192
Tel (03) 9545 4100
Tel 1300 84 74 66
Tips for using magnifiers
Successful use of a magnifier is a sophisticated skill, particularly for children, and generally requires considerable training and practise.
- ensure that the lighting is appropriate – shining a lamp directly onto the task from over the shoulder may assist
- use the magnifier either with the naked eye or spectacles as recommended by the student’s optometrist
- when reading textual materials with a magnifier, it may be helpful to mark the line with a finger. When reaching the end of a line of print, track backwards along the line to the beginning of the line marked with the finger, then drop down to the line below.
- hold the magnifier close to the eye and bring the object towards the magnifier until it is focused – this will ensure the greatest field of view
- some readers prefer to move the book or page from side to side rather than moving the magnifier or their eyes
- if reading while seated in a chair, consider placing a tray, cushion or clipboard beneath the book or newspaper to help keep the page flat
- keep the magnifier clean by using a lens-cleaner
- protect the magnifier from scratches by storing carefully when not in use
In an article printed in the Spring 2000 edition of Lighthouse International’s EnVision Newsletter Anne Corn (Professor of Special Education, Peabody College, Vanderbilt University, Nashville, Tennessee) identifies four factors in addition to the right prescription which need to be considered when determining suitable magnification devices for children:
- Motivation: Optical devices can allow children who have low vision to participate in class activities. With a monocular, for example, a child can sit with their classmates while the teacher reads a picture story. Older students can read bulletin board postings that are not available in large print.
- Appearance makes a difference: Children want to fit in with their peer group and may feel self-conscious using “obvious” devices. Hand-held magnifiers and monoculars should be chosen with appearance in mind. Young children may like to decorate their devices and carrying cases.
- Duration of activity affects skills: Begin with activities of short duration, such as reading a wristwatch or an item on a menu, to help children get started using near vision devices. Learning to use a device well before it’s needed in the classroom is advantageous.
- Quick retrieval of devices and coordination are important: Children should be taught good mechanical skills, including one-hand focusing of monoculars, as well as how to change the angle of a hand-held magnifier to accommodate light and comfort.
For further information please check with the equipment supplier.