Bi0ptic Telescopes Prescribing decisions, the patient and the training

1
Bi0ptic TelescopesPrescribing decisions, the
patient and the training

• Ian L Bailey, OD, MS, FCOptom, FAAO
• School of Optometry
• University of California, Berkeley. CA 94720-2020
• bailey_at_spectacle.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
• Principles
• 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 allow or deny licensure, and to
  impose 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
  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 might reduce field of view
• Brightness may be reduced
• Head and/or eye movements are required to
  interchange

6
Is seeing fine detail important to driving?

• Yes!
• Reading signs
• (freeway signs, street signs, warnings,
  regulations, house numbers, building signs)
• Traffic signs size and position usually
  designed on assumptions that
• drivers will have a visual acuity of 6/12
  (20/ 40 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

7
BiOptic telescopes allow fine details to be seen
from a longer distance

• If a driver obtains 20/40 or better through
  telescope,
• he may be enabled 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)
8
Illustration of RING SCOTOMA with 3x telescope

For a 3x telescope Occluded area is 8x larger
than the area being magnified
9
Projecting a telescope ring scotoma

10
Ring scotoma could be hazardous

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

11
Some visual criteria for selecting patients for
bioptic telescopes for driving

• Best corrected Visual Acuity - 6/48 to 6/15
  range (20/160 to 20/50)
• Telescope V A (M 4x or less) - 6/12 to
  6/9.5 range (20/40 to 20/32)
• 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 6/120 or better
  (20/400)
• Second eye should not have profound suppression

12
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

13
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

14
Before prescribing Advising the patient

• 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

15
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 nose pads to vary height and
  lateral position
• Determine lens powers for telescope and carrier
  lens
• Select characteristics of carrier lens (SV,
  bifocal, tint)

16
For positioning angling bioptic telescopes

17
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, engage
  telescope)
• WHEN patient is proficient with telescope while a
  passenger
• THEN we issue DMV report form
• AND patient begins training with professional
  driving instructor

18
Test Cards for bioptic telescope evaluations

19
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

20
Driving test with Department of Motor Vehicles

• Driving test appointment with a Driver Safety
  Referee
• Driving test
• Longer course than usual
• Exposure to more visually-demanding driving
  tasks
• Individual consideration
• May consider experience and need
• May impose restrictions - times, routes, use of
  bioptics, etc
• Night time drive test may be requested
• if patient wants to remove no night driving
  restriction

21
Issue of a Driving License by Department of
Motor Vehicles

• If driving test is passed, the Driver Safety
  Referee may issue
• Unrestricted License OR a 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

22
Summary

• 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 an
• opportunity to demonstrate ability to drive
  safely
• It can be reasonable to have definite limits
• OPINIONS New California limit of better than
  20/200 (6/60) is acceptable
• No driving with hemianopia is
  reasonable

23
Thank you!

bailey_at_spectacle.berkeley.edu