Transcript Henry Greene - BiOptic Driving Network

Prescribing Bioptic
Telescopes
Qualify, Demonstrate, Indoctrinate, Recruit
Henry A. Greene, OD, FAAO
Reading is a solitary activity
 Most
responsive to low vision aids
high contrast
 controllable environment

 Reading
is the most easily replaced visual
activity
talking books
 radio, TV
 sighted support

Distance Vision is a Social
Activity
 Seeing
faces
 Interpersonal relations
Non-verbal body language
 Making eye contact

 Avoidance
of isolation
 Quality of life
“Before I got the telescope, my world
extended to the end of my arms. The
telescope made my arms 4 times longer”
“Visual Radius”
 Derived

from Proximal Magnification
Moving closer makes the retinal image larger
 The
furthest distance at which one can
discern facial features

Under normal illumination
 Visual Acuity
Correlate
2 feet = 20/200
 1 foot = 20/400

The Telescope “Face” Test

A good response to high contrast targets is not
prognostic
 The face is a convenient low contrast target
 Seeing a face well through a TS at 8-10 feet is
prognostic of magnification response
 Poor response associated with edematous maculas
“Visual Radius” and “Social Range”
 “Social
Range”- 3 to 15 feet
 Expand the “Visual Radius” sufficiently into
the “Social Range”
 Telescopes extend the visual radius by the
power of the device
 With a 4x telescope:
2 feet becomes 8 feet
 6 inches becomes 24 inches

TS Prescribing Paradigm Summary

Identify the furthest distance that a face can be
seen- “Visual Radius”
 Confirm a favorable response to telescope
magnification- “Face Test”
 Extend the “Visual Radius” into the “Social Range”
 Establish realistic goals and expectations
Magnification is not natural.

Constraints of Magnification




Working Distance
Shallow Dept of Field
Narrow Field of View
Constraints on the patient




Unnatural working distances
Disorientation
Inconvenience
Fatigue
What are bioptics?

Eyeglasses with a miniature built-in telescope
 Allow use of normal and magnified vision by simply
tilting the head- like “upside down bifocals”
 Do not interfere with walking
 Help you see things further away:



Spotting- like the use of rear and side view mirrors
Continuous tasks- TV, computer
Best for midrange and beyond

Not ideal for reading
Basic Optical Concepts

Galilean vs. Keplerian
 Larger objective lens:



Larger, multi-element eyepiece:


Brighter image
Shallower depth of field
wider FOV
Longer eye-relief:

Narrower FOV
Characteristics of Bioptics
Galilean
Keplerian
Size
Small, Very Small
Big, Bigger
Shape
Std. Tube
Micro
Std. Tube
HLP, BTL
Focusing
Fixed, Manual
Manual, AF
Powers
1.8 – 8x
3 – 8x
Fields
4x
Narrow
5 deg
Less Narrow
12.5 deg
Optics vs. electronics
Optics
Electronics
Image Resolution
High
Low to moderate
Brightness
Inside variable
Outside good
Inside good
Outside poor
FOV- 4x
12.5 deg
40 at 1x; 10 at 4x
Power range
Fixed
Zoom
Ease of Operation
variable
variable
Mobility with aid
Easy
Variable to none
Weight
variable
Variable to ugh!
How much power?

Enough magnification to achieve the goal
 Acuity demand:
Average
 High

 Sporting
~20/40 goal
~20/30 goal
events?
 More than 6x is tough to keep stable on the head
 More than 7x- time for binoculars
How much Field?

What is a degree?
 How much FOV is enough?



It’s never enough- minimum ~ 5 deg
Use comparisons- TV; rear view mirror
It gets more natural

Maximize for close distances
 Let the patient compare using handhelds

4x12 Keplerian vs. 3x Galilean
User issues regarding bioptics

Low Vision Device Use Among Veterans



Watson, et.al., OVS, 74:5, May 1997
200 veterans, 740 devices, 130 spectacle TS
Issues:
 Wider FOV Autofocus More power Brighter image Less noticeable
83%
79%
78%
49%
16%
When to AF and when to not…

Acuity between 20/70 and 20/200
 Room and mid-range activities


Dexterity issues


Not for >20’
Tremors, Paresis
Application issues

Hands-free activities
Courtesy CNN
Which eye? Or both?

Prescribe for the dominant eye if at all possible


Binocular systems



Suppression difficulties significantly undermine acceptance
Challenging to keep aligned- Very stiff frame, Beecher
Wider FOV, Acuity and CST summation, no suppression issues,
lessens impact of scotomas
Binocular Working distance fixed
Monocular is easier
What position?

Types of mountings:

Permanent (glued) vs. adjustable

Minimum 3mm above eyepiece to top of lens
 Align the bottom of eyepiece to top of pupil
 The higher the eyepiece= the higher the TS angle


the greater the head translation
Lower and straighter position for
midrange applications
 Use a head strap
 Use wide nosepads
Carrier lens issues

Use their habitual distance Rx



Minimum 10mm between bottom of eyepiece and
top of seg



Single vision or multifocal
Avoid progressives and trifocals
Seg high but not too high
Low but not too low
Avoid polycarbonate lenses- hi index OK

Tough to drill
Qualify the Patient
 Not
all patients are bioptic candidates
 Establish

a prognosis for likely success
The Clinical Evaluation
 Address
Finances and Appearance
This is not cheap-- “Is it worth it to you?”
 “It looks a little unusual-- will you wear it?”

 You’ll

have to learn to use it
Are you prepared to make the effort?
Qualify the patient:
Establish a telescope prognosis

Hard Signs
1. VA between 20/70 and 20/300 (faces >2 feet)
VA gain with 4x TS? Fluency
2. Response to low contrast target
Faces at 10 feet through 4x12 TS
3. Better eye is dominant

Soft Signs
1. Appropriate goals: mid-range and beyond
2. Motivation: appearance, enthusiasm
3. Dexterity
Test and demonstrate with Handheld
Telescopes first


Handheld 4x12- prefocus!
Determine the dominant eye


Which eye do they take the TS to?
Evaluate response to faces at ~10 ft

Poor response undermines prognosis


Needs brighter image
Show:



Narrow FOV- challenges in finding the target
Shallow DOF- challenges in keeping clear
Need to refocus- challenges in doing the activity
Demonstrate Bioptics next

Get them out of the exam chair
 Present the concept of the “Magnification Factor”


Realistic experiences= realistic expectations


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With a 4x TS- What you see at 2’, you’ll see it at 8’
The “Eye Chart” is NOT the “real world”
“Grocery Store,” CRT, Pictures on walls
Sit in the “living room” (Waiting room)
Outside- signs, flowers, faces
Use your assistant
 Have family accompany
Recruiting the Patient
“We can teach them to ride the bike,
but they have to do the pedaling.”
 The patient’s job:





To want to improve their vision
To make the effort to learn to use it
To be frustrated
To invest time and $
Training Techniques

Sighting through eyepiece

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Translation


Aiming and Switching
Tracking


Switching between carrier and eyepiece
Localization


Give them a tour of the device
Moving targets
Near localization and hand-eye coordination

Finding the target