Bi0ptic Telescopes The patient, the decisions, and the training - PowerPoint PPT Presentation

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Bi0ptic Telescopes The patient, the decisions, and the training

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Arranged to allow easy interchange from viewing with and without the telescope ... A driver who obtains 20/40 or better through telescope, ... – PowerPoint PPT presentation

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Title: Bi0ptic Telescopes The patient, the decisions, and the training


1
Bi0ptic Telescopes The patient, the decisions,
and the training
  • Ian L Bailey, OD, DSc, FAAO
  • School of Optometry
  • University of California, Berkeley. CA 94720-2020
  • ibailey_at_berkeley.edu

2
Basic Vision Functions and Driving
  • Visual acuity reading signs, seeing detail
  • Contrast sensitivity seeing larger objects,
    borders, textures
  • Visual fields seeing things to the side
  • Color vision ability to see traffic signals,
    warning lights
  • Glare veiling haze from headlights or
    bright light
  • Adaptation (light/dark) adjusting to
    changes in light level
  • Light sensitivity ability to see in dim
    conditions

3
Should visually impaired people be allowed to
drive? The Dilemma
  • For denial to be justified
  • Evidence of individual incompetence
  • Evidence (associations) of highly elevated
    risk
  • Strong prima facie argument for highly
    elevated risk
  • Caution when considering statistical evidence
  • Associations describe trends - they are not
    rules
  • Higher crash rates for a given group is
    insufficient,
  • by itself, to disqualify all members of that
    group

4
Should visually impaired people be allowed to
drive?
  • Licensing Authorities (DMVs) have the
    responsibility
  • to test driving abilities, to allow or deny
    licensure,
  • and to impose any restrictions
  • They may consider Special driving tests
  • Past driving experience
  • Anticipated driving needs
  • Causative disorder
  • Other health issues (sensory,
    motor, cognitive)
  • They may impose Closer monitoring of
    driving record
  • More frequent vision and driving tests
  • Restrictions on routes, time of day,
    etc.
  • Restricted vehicle
    categories, speed
  • They may require BiOptic telescopes

5
What is the use of BiOptic Telescopes?
  • BiOptic telescopes are
  • Head mounted telescopes Typically magnification
    (for driving) 2x to 4x
  • Arranged to allow easy interchange from viewing
    with and without the telescope
  • BiOptic telescopes magnify
  • Enable distant details to been seen to be seen
    more easily.
  • Advantages for driving
  • Signs, signals and other features with more
    small details
  • can be seen at a longer distance than they
    otherwise could be
  • Disadvantages
  • Ring scotoma can reduce field of view
  • Brightness may be reduced
  • Head and/or eye movements are required to
    interchange

6
Vision impairment and Nystagmus
  • Congential Nystagmus Reduced visual acuity
  • Normal contrast sensitivity
  • Normal visual fields
    Astigmatism
  • Albinism Reduced visual acuity
  • Normal contrast sensitivity
  • Normal visual fields Astigmatism, High
    refractive error ()
  • Some sensitivity to light
  • Achromatopsia Reduced visual acuity
  • Reduced contrast sensitivity (somewhat)
  • Normal visual fields
  • Poor color discrimination
  • Photophobia
  • Astigmatism, High myopia in some (Blue cone)

7
Is seeing fine detail important to driving?
  • Yes!
  • Reading signs
  • (freeway signs, street signs, warnings, parking,
    house numbers, building signs)
  • Traffic signs size and location usually
    designed on assumptions that
  • drivers will have a visual acuity of 20/40
    (6/ 12 or 0.5)
  • But!
  • Reading signs, or attending to fine details
  • required for short-term and infrequent
    driving tasks
  • Especially in familiar areas, and other
    situations where need to read signs is minimal

8
BiOptic telescopes allow fine details to be seen
from a longer distance
  • A driver who obtains 20/40 or better through
    telescope,
  • should be able to read roadway signs, etc., from
    the intended distance

BiOptic telescopes only engaged intermittently
for short periods when attending to signs (or
other fine detail)
BUT Potential danger when looking through
telescope because part of visual field is
occluded (RING SCOTOMA)
9
Illustration of RING SCOTOMA with 3x telescope

For a 3x telescope Occluded area is 8x larger
than the area being magnified
10
Projecting a telescope ring scotoma

11
Ring scotoma could be hazardous
  • When viewing through telescope. There must be
  • a substantial para-central field loss from the
    ring scotoma,
  • IF -- the second eye is occluded
  • OR -- if the second eye is functionally blind
  • OR -- if there is a binocular telescope system
  • BUT
  • When viewing through telescope, there is no
    field loss
  • Provided -- second eye does not have a
    telescope
  • remains open
  • can
    readily detect large peripheral objects
  • does not have profound suppression

12
Some visual criteria for selecting patients for
BiOptic Telescopes for driving
  • Best corrected Visual Acuity - 20/160 to 20/50
    range (6/48 to 6/15)
  • Telescope V A (M 4x or less) - 20/40 to
    20/32 range (6/12 to 6/9.5)
  • Should not have more than a 3x (0.5 log units)
    reduction in CS
  • Should not have significant field defects
  • Telescope before one eye only (better reading
    eye)
  • Second eye should have VA of 20/400 or better
    (6/120)
  • Second eye should not have profound suppression

13
Before prescribingOptometric consideration of
visual abilities
  • Hard numbers on Visual acuity
  • Contrast
    sensitivity Visual fields
  • Evaluate as needed Color vision
    Glare
    Adaptation (light/dark)
  • Light sensitivity
  • Consider Motor and mental agility
  • Reaction time
  • Vision in clutter
  • Divided attention

14
Some variations on usual more common tests
Visual Acuity Reading efficiency for words and
sentences
10 M 8.0 6.3 5.0 4.03.2 2.5 2.0 1.6 1.25 1.0 0.8
0.63 0.5 0.4 0.32 0.25 0.2
Word Reading 10 words each size Grade 3 word lists

Put your first name on this paper
Sentences 60 characters MNRead
if you will help tomorrow
Many people came to help us
clean the place after the party
15
Some variations on usual more common tests
Visual Fields Effect of illumination
  • Variable luminance backgrounds
  • EITHER
  • Plot fields
  • OR
  • Ask about letters visible on chart
  • at different luminances
  • RP, ARM etc
  • fields change with luminance

16
Some variations on usual more common tests
Contrast Sensitivity Response Efficiency Tests
  • Number search
    Flashing squares
  • Output display
    Less than 2 mins per test
  • Response time 2 measures at 24 contrasts
  • vs Log CS

17
Some variations on usual more common tests
Useful Field of View (UFOV)
  • Test patients ability to respond to peripheral
    stimuli
  • Delayed reaction times for peripheral visual
    stimuli
  • Failure to see brief, peripheral visual stimuli
  • (i.e., reduced measured visual
    field)
  • When there is Divided visual attention
  • Visual clutter
  • Multi-tasking

18
Before prescribingEnsure good skill using
telescopes
  • Hand held telescope - magnification equal to, or
    stronger, than planned bioptic
  • Achieve 20/40 with telescope
  • Efficient spot viewing - both indoors and
    outdoors
  • stationary observer - stationary object of
    regard
  • stationary observer - moving object of regard
  • moving observer - stationary object of
    regard
  • moving observer - moving object of regard
  • Real world location and viewing of targets in
    visual clutter
  • first locate the target object, and then
    engage telescope

19
Before prescribing Advising the patient
  • Advise patients about their visual disabilities
    and functional relevance
  • Bioptic telescope does not ensure ability to pass
    driving test
  • Bioptic telescopes do not restore vision to
    normal
  • Even with bioptic telescopes, they remain at a
    visual disadvantage
  • Need to drive with extra caution
  • Should have companion drive when possible
  • Need practice in viewing with bioptic telescope
    system
  • Need supervised training using bioptic telescope
    for driving
  • If no driving experience, likely to need more
    instruction than usual from
  • a professional driving instructor
  • The DMV makes the final decisions

20
Prescribing BiOptic Telescopes
  • Select telescope Magnification
  • Design (Designs for Vision, Ocutech)
  • Galilean, smaller, light weight, small
    field
  • Keplerian, longer, heavier, larger field
  • Focus fixed, adjustable, auto
  • Exit Pupil smaller or larger
    than pupil
  • Select frame Suitable for telescope mounting
  • Sturdy and comfortable
  • Adjustable to vary height, lateral
    position and angle
  • Determine lens powers for telescope and carrier
    lens
  • Select characteristics of carrier lens (SV,
    bifocal, tint)

21
PrescribingPositioning Angling BiOptic
Telescopes

22
Training Using a BiOptic Telescope
  • Rehabilitation Staff
  • Five to fifteen lessons of 30 minutes.
  • Home practice after each lesson Begin
    practice indoors with flash cards,
  • Practice outdoors while walking (include
    traffic signs)
  • Practice while a passenger in a car
  • residential, business and freeways
  • (locate signs, signals, landmarks and then
    engage telescope)
  • WHEN patient is proficient with telescope while a
    passenger
  • THEN we issue DMV report form, patient applies
    for permit
  • AND patient begins training with professional
    driving instructor

23
TrainingTest Cards for bioptic telescope
evaluations

24
Dealing with the Department of Motor Vehicles
  • Appointment with a Driver Safety Referee
  • Present vision report that includes information
  • VA with and without telescope
  • Fields, contrast sensitivity
  • Causative eye disease or disorder, stability
    and prognosis
  • May be considered a learners permit
  • THEN the patient takes the written test
  • THEN driving permit may be issued
  • LATER, patient takes drive test

25
Department of Motor Vehicles Driving test
  • Driving test appointment with a Driver Safety
    Referee
  • Driving test
  • Longer course than usual
  • Exposure to more visually-demanding driving
    tasks
  • Night time drive test may be requested
  • if patient wants to remove no night driving
    restriction

26
Department of Motor Vehicles Issue of a Driving
License
  • Unrestricted or Restricted License??
  • Special considerations Driving skill tests
    Causal disease
  • Driving experience Visual abilities
  • Driving record Extent of vision loss
  • Driving need Prognosis, stability
  • Anticipated driving Variability of
    vision Sensory motor disabilities Other
    visual disabilities
  • Special constraints
  • Monitor Accidents Violations
  • Increase frequency Renewal Vision reports
  • Driving tests
  • Restrict Time of day Visibility
    conditions Routes Purpose
  • Distance from home Vehicle category
  • Require BiOptic Telescope Special mirrors

27
Some Conclusions
  • Visual acuity tasks much less important
  • than visual field
    and contrast sensitivity tasks
  • BiOptic Telescopes enable seeing of finer
    detail,
  • when
    needed
  • Visually impaired drivers should be given
    opportunity
  • to
    demonstrate ability to drive safely
  • It can be reasonable to specify definite limits
  • OPINIONS New California limit -better than
    20/200 (6/60) -is acceptable
  • No driving with hemianopia is
    reasonable

28
Thank you!

ibailey_at_berkeley.edu
29
For Europe
  • POLICIES TO DEMAND
  • BiOptic telescope is a corrective lens system
  • Telescope must allow visual acuity of 6/12 (20/40
    or 0.5)
  • Telescope must be before one eye only
  • BiOptics are to be used with two eyes open
  • so, relevant visual field test is with both
    eyes open
  • COMPROMISES TO ACCEPT OR CONCEDE
  • Vision report every 5 years (at least)
  • Maximum mag 4x, or without TS, VA gt 6/48
    (20/160 or 0.125)
  • Driving should be conditional on wearing
    telescope
  • Initial license should be for daytime use only
  • Night driving cannot be considered until 3 years
    experience
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