Title: Bi0ptic Telescopes The patient, the decisions, and the training
1Bi0ptic 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
2Basic 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
3Should 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
5What 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
6Vision 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)
-
7Is 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
8BiOptic 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)
9Illustration of RING SCOTOMA with 3x telescope
For a 3x telescope Occluded area is 8x larger
than the area being magnified
10Projecting a telescope ring scotoma
11Ring 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
12Some 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
13Before 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
14Some 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
15Some 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
16Some 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
17Some 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
18Before 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
19Before 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
20Prescribing 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)
21PrescribingPositioning Angling BiOptic
Telescopes
22Training 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
23TrainingTest Cards for bioptic telescope
evaluations
24Dealing 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
25Department 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
26Department 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
27Some 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
28Thank you!
ibailey_at_berkeley.edu
29For 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