Eschenbach Low Vision Training Program
Edited by:Thomas Porter, ODAsst. Professor & DirectorLow Vision ServiceSt. Louis University, Dept. of Ophthalmology
© 2015 Eschenbach Optik of America, Inc. (Ver. 1)
Module 8: Video Magnifiers
© 2017 Eschenbach Optik of America, Inc. (Ver. 2)
Low Vision Training Module #8
The Seven Steps to Dispensing Low Vision Aids®
1. Make sure the patient is under the current care of an eye doctor and has a current refraction
2. Identify the patient’s visual goals
3. Determine the magnification required
4. Demonstrate the impact of illumination
5. Select the appropriate vision aids for the goals identified
6. Train the patient in the use and care of the chosen vision aid
7. Schedule a follow-up visit
Low Vision Training Module #8
Video Magnifiers……provide the highest levels of magnification available…are the only devices that allow the user to alter the image of the object being viewed
…work based on the combined principles of projection and relative distance magnification
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• What they are
• How they work
• How to use
• Types available
• What are they made for
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What is a video magnifier?
An electronic device that magnifies an object for viewing by the user through the use of a camera that projects an enlarged image of an object on a screen or monitor.
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How do Video Magnifiers work?
XY
Monitor
X/Y Table
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Rules for using video magnifiers properly:
1. Locate the object to be viewed with video camera (and focus on high magnification if not an autofocus system)
2. Adjust magnification and move object/camera to cover area to be viewed
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1. Locate the object to be viewed with video camera (and focus if the device is not auto-focus)
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2. Move object/camera to cover area to be viewed
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Video Magnifier Display Options
Normal
Reverse Polarity False color
High Contrast
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Video Magnifier Display Options
Windowing / Blinds
UnderlineFalse Color, cont.
Full Color
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Tips for use of Video Magnifiers:•Make sure reading materials are positioned “squarely” on the X-Y table
•Test reverse polarity and color combinations to determine most comfortable image for user
•Monitor height should be adjusted to avoid neck fatigue
•Proper body posture should be used
•Consider near correction required for accommodation
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Equivalent Power
Equivalent Power (EP) for Near =
Screen Magnification X Accommodation
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EP = Screen Magnification X Accommodation
EP = Screen Size
Object SizeX
1 meter
Viewing Distance (mm)
Viewing Distance
Screen Size
Object Size
Screen Size
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Example 1:A user puts their favorite book under a video magnifier. The screen image of the print is 20mm whereas the original print size is 1mm. They can read this comfortably at 16” from the display. How much power are they deriving?
EP = Screen Magnification X Accommodation
Solution:
EP = 50 D
X (40”/16”)EP = (20mm/1mm)
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There are four different design types of video magnifiers:
• Portable / Hand-held Video Magnifiers
• Desktop Video Magnifiers
• Desktop with Distance/Near Camera
• Head-born Video Magnifiers
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Portable / Hand-held Video Magnifiers
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Desktop Video Magnifiers
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Desktop Video Magnifiers with Distance/Near Camera
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Head Borne Video Magnifiers
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Video Magnifiers exist for tasks at all distances!
NearSpotting
NearExtended
Inter-mediateSpotting
Inter-mediate
Extended
DistanceSpotting
DistanceExtended
Hand-Held √
Stand √Spectacles √
Telescopes √ √ √ √ √ √
Video √ √ √ √ √ √
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Video Magnifier Applications
Looking at photographsReading a book or magazine
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Video Magnifier Applications
HandwritingReading recipes
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Video Magnifier Applications
In the classroom In the office
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“Integrated” System
NTSC Signal
VGA Signal
Serial Connection
USB Connection
(National Television System Committee) analog television signal standard
(Video Graphics Array) analog computer display standard
Computer connection where data is transferred one bit at a time.Usually used for connection of peripheral hardware.
(Universal Serial Bus) connection that allows more than one peripheral to connect to a single socket facilitating “hot swapping” and “Plug ‘n Play”
Video system where display, camera and power source are housed in one unit
RCA ConnectionAn RCA jack is a type of electrical connector that is commonly used in the audio/video market.
VideoMagnifierTerms
Low Vision Training Module #8
• What they are
• How they work
• How to use them
• What types are available
• What are they made for
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Questions?
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Thank You!
