Magnification Strategies and Large Print Resources for Visual Impairment

Fundamental Principles of Magnification

Objective of Magnification: All magnification strategies aim to produce a larger retinal image. The goal is for this image to be sufficiently large for the patient to recognise, even when ocular pathology results in impaired visual acuity (VA).
Relativity of Magnification: Magnification is a relative value and cannot be $0$ . It must be either >1 or <1. For low vision assistance, the value required is >1.
Typical Magnification Ranges (Approximate):
Changing Object Size/Distance: Typical values range from $1.5times$ to $5times$
Devices: Typical values range from $1.5 imes$ to $20 imes$ .
Electronic Devices: Typical values range from $3 imes$ to $100 imes$ .
Comparison with Spectacle Magnification: Spectacle magnification is the effect caused by the plus or minus lenses used to correct ametropia.
Image Size Effects: Minus lenses tend to minify (make images smaller), while plus lenses magnify (make images bigger). This affects the size of the image on the retina. For example, a high myope wearing spectacles may have slightly poorer VA compared to when they are wearing contact lenses due to this minification.
Cosmetic Effects: The observer also sees the spectacle wearer’s eyes as minified or magnified based on the lens type.
Magnitude: This effect is very small compared to low vision aids, occurring at a rate of approximately $1\%$ per dioptre.
Conversion to Percentages: A magnification of $2 imes$ is equivalent to $200\%$ . A magnification of $10 imes$ is equivalent to $1000\%$ .

Increasing Object Size: Large Print Books

Overview: Increasing the physical size of the object (such as large print) is the most common example of changing object size to aid vision. It is primarily used for near tasks.
Historical Context: The first large print books in the UK were the Ulverscroft series. * This series was pioneered in $1964$ by Mr Thorpe, a retired publisher.
Availability: These books are available for purchase (via mail order) or can be borrowed from public libraries.
Specifications: Print Size: Usually $\approx1.5-2times$ the size of ‘normal’ print. To put this in perspective, large print is typically at least $16$ point, compared to standard $10$ point.
Standards: There is no official ‘standard’ for the exact size, font type, or spacing required for a book to be classed as ‘large print’.
Format: These books are usually hardback rather than paperback.
Content and Publishers: Commercial Providers: Focus on popular fiction, dictionaries, hymn books, bibles, cookbooks, and autobiographies. Specialist Publishers: Various links exist for specific needs (check Bb resources). RNIB National Library Service: Provides resources for large print materials.
Modern Production Technique: Technology now allows large print versions to be ready at the same time as standard versions. Print on Demand: Publishers can print books as they are ordered to avoid the financial risk of unsold stock. This encourages mainstream publishers to stay involved in the large print market.

Advantages and Disadvantages of Large Print

Advantages:
Requires no change in the user’s reading posture.
Allows for a ‘normal’ working distance.
Permits binocular viewing.
Disadvantages:
Portability: The books are physically larger and heavier.
Availability: There is limited availability of titles, especially for technical subjects and children’s literature (though children’s books are often large by default). Only $1.5\%$ of the $2$ million books currently in print worldwide are available in large print.
Cost: They are more expensive to buy due to being hardback and having shorter print runs.
Paper Quality: The paper is often very thin, which can lead to ‘ghosting’ or seeing words on the reverse side of the page.

Giant Print and Periodicals

Giant Print: * Set at $24$ point size. * The range is more limited but includes children’s books. * Published by and available for loan from the RNIB.
Magazines and Newspapers: * Puzzle Magazines: Large print versions of crosswords and sudoku are widely available in the UK, often through subscription. * Big Print: A weekly UK publication available by mail order. It provides a digest of stories, crosswords, and TV listings. * Sideview: This is the official newsletter of the Macular Society.

Practical and Everyday Applications of Large Print

Daily Living Aids:
Telephones: Large button models are available.
Remote Controls: Universal large-print remotes.
Hobbies: Knitting patterns and music sheets (Large Music).
Essential Documents: Utility bills and bank statements (available in large print on request).
Instructional Materials: Information leaflets.
Large Screens: Using a large screen TV provides a larger image, though only limited size changes are possible compared to other methods.

Computing and Specialist Software

Hardware Solutions: Large monitors, specifically flat screens mounted on movable arms for better positioning. Keyboards with large print or high-visibility key labels (often featuring reverse contrast).
Specialist Accessibility Software: Major Products: Zoomtext and Dolphin Supernova.
Capabilities:
Magnification up to $32\times$ .
Significant changes to colour, contrast, and brightness.
Customization of the cursor (colour, size, and movement speed/trails).
Full screen reading and narration of all system operations.
Nuance Dragon NaturallySpeaking: Primarily a voice-to-text system. Not originally aimed at the visually impaired, so interacting with the system to set it up or navigate may still require some level of vision.
Native Windows Features: Access via the ‘Ease of Access Centre’ in the Control Panel. * Provides audio narration of text and various system-wide accessibility prompts. Keyboard Shortcut: The command left shift + alt + PrtScr (Print Screen) is a quick way to toggle accessibility/contrast features.
Interface Examples: Tools like Outlook and standard desktop software can be adjusted to show larger text, unread mail counts (e.g., $1743$ ), and simplified folders to manage high-volume communication.