Title: Electronic Magnification CCTV
1Electronic Magnification (CCTV)
Mouse Unit EVS Max
Stand alone unit Telesensory
2Flipper port EVS
Videoeye Swing Arm
Max port Head Worn
3Electronic Magnification
- Advantages
- Can significantly increase size
- Controls for contrast and glare
- Portable depending on model
- Versatile
- Permits binocular use of eyes
- Preserves field of view
4Electronic Magnification
- Disadvantages
- Expensive
- 350 and up
- Cheaper models are not portable
- Can be difficult to wear and to position
- Higher cognitive demand
- Sometimes difficult to tolerate motion
- Perceived as high tech by older users
5Patients should always wear their eyeglasses when
using any magnifier
- Eyeglasses correct for refractive errors
- Hand held magnifier should be viewed through
DISTANCE CORRECTION
- Stand magnifier should be viewed through READING
ADD
6Telescopes
- Used to view objects at a distance
- Have different focusing ranges
- Afocal
- Focuses beyond 20 feet
- Reading cap
- Permits focusing distance of 16-18 inches
7Telescope Design
Objective lens
Ocular lens
8Exit pupil is the optical window the patient
views through
Exit pupil
Higher the magnification, the smaller the exit
pupil
9Telescopes Come in Two Basic Styles
- Galilean
- Used for most low vision
- Smaller and lighter weight
- Keplerian
- Astronomical telescope
- Has a larger exit pupil
- But weighs more
10Strength of Telescopes
- Label indicates power and field of view
- Example
- 6 x 30 telescope
- 6x power and a 30mm objective lens
-
11Challenges Using Telescopes
- Motion Parallax
- Movement is exaggerated through the telescope
- Creates a speed smear (described as bouncing)
when used in dynamic situation
- Difficult to adjust to, reduces accuracy
12Challenges cont.
- Objects appear closer than they really are
- Generally the field of view is very small unless
the magnifier is really bulky
- Lose light- images appear darker
13For maximum image brightness, the exit pupil
should match the patients pupil
- To determine the size of the exit pupil
- Divide the diameter of the objective lens by the
power of the magnifier
- Example
- 6 x 30 magnifier
- 30 5 mm
- 6
14- Measure the width of the patients pupil using a
metric ruler and compare
- If the exit pupil is smaller than the patients
pupil, the image will be dark
- To correct-try a telescope with a larger exit
pupil
15Clip-on Monocular
- For short term or periodic telescopic needs
16Bioptic (for continuous use)
- Used in combination with carrier lens
- Carrier is used for most activities-bioptic for
detail
- Dip head to view through biotic
- Limited field, motion parallax
17Full Field Binocular
- Covers entire lens in frame
- often used to view sporting events /TV
- sportscopes
- Doesnt allow viewer to look around
- Can only use when stationary
- Heavy-can be hard on nose bridge and ears
18Clip on monocular
Head worn binocular
19Automatic Focusing Telescopes
Monocular
Binocular
from Ocutech
20Some persons can be fitted with a contact lens
system
- High minus power serves as the ocular lens
- Plus spectacle worn as the objective lens
- Provides a 50 degree visual field with 2x
magnification
21Miscellaneous stuff.
- Monocular telescope powers
- 2.5x, 2.8x, 3x, 4x, 6x, 8x, 10x
- Spectacle powers
- 2x, 2.2x, 3x, 4x, 6x, 8x
- For monoculars, person should always wear glasses
unless instructed not to
- Correct for astigmatism
22Telemicroscope
- Combination microscope and telescope
- Usually spectacle mounted
- Generally a microscope cap is placed on a
telescope lens
- Gives advantage of microscope magnification at a
longer focal distance
23 Telemicroscope