Objectives of presentation Educate - basics re bioptic driving
Educate - common misconceptions Provide update of bioptic driving
activities, USA & abroad 4
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Why the confusion re bioptic driving? (Part II) 5
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Common misconceptions Optics of device Users ability to see
Basic use of device Use in familiar areas 6
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Misconception No. 1 The optical limitations far outweigh the
optical advantages of bioptic lens systems; making such devices
unsafe for use during driving.
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Optical limitations Nearness illusion - Objects or forms appear
closer - Depends on level of magnification - In reality,
object/form is X times farther away - Jack in-the-box effect 8
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Jack in the box effect Other road users that suddenly and
unexpectedly move into the magnified or non- magnified field of
view or path of travel
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Developing Jack in the box 10
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Jack in the box effect 11
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Concern of Jack in the Box Oncoming, lateral, same direction
Sudden braking, rear-end accidents Rationale for short fixations
12
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Optical limitations (contd) Restricted magnified field of view
- Dependent on (X) Power, type and size of telescopic units -
Dependent on vertex distance 13
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Sampling: telescopic fields of view Manufacturer Field of view
(degrees) DVI - 2.2X BIO I, BIO II Galilean.. 12, 11 - 3.0X WA BIO
I; 3X BIO I, 4X BIO I Galilean.... 11, 8, 6 Ocutech - 1.7X, 2.2X
Sight Scope Flip.... 26, 18 - 3.0X Mini . 15 - 4X VES K .. 12
Conforma - 4X BITA....... 8.5 14
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Vertex distance Linear distance or space between center of
cornea and center of carrier lens, or center of ocular lens of
telescopic unit Bioptics are not horse blinders 15
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Optical limitations (contd) Ring scotoma part of the normal
visual scene invisible to the user Created by the enlarged retinal
image produced by telescope (overlaps part of the normal visual
image) 16
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What photo of ring scotoma does not tell you? Scotoma exists
for a few milliseconds (intermittent vs. continuous viewing) Extent
of non- magnified field Impact of 1 vs. 2 telescopes *Source: Randy
Jose, O.D., 2011 SWOMA Conference 17
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Normal visual field Visual field of one eye overlaps visual
field of other eye Central macular vision that is often impaired in
bioptic drivers accounts for a small amount of field *Source: Dr.
Laura S. Miller, O.D. (ww.nwhillseyecare.com) 18
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Optical limitations (contd) Apparent movement of visual scene
(objects or forms) in opposite direction to head movement -
Consistent with all types of devices that magnify or enlarge -
Rationale for vertical spotting only
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Apparent movement of object or form opposite to head movement
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Apparent movement of object or form opposite to head movement
21
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Apparent movement of object or form opposite to head movement
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Optical advantage Increases margin of safety - the time or
distance needed to detect and identify a critical object or
condition; then predict, decide and execute an appropriate driving
maneuver.
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Optical advantage Allows bioptic user to detect and identify
detail, color and activity of distant objects or forms at farther
distances 24
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Approach magnification Driving slower and closer to critical
object(s) or critical situations before making a decision of what
to do or not do 25
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Misconception No. 2 Low vision drivers depend upon the
telescopic portion of their bioptic lens system to see.
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In reality Low vision drivers can see in the distance, but not
distinctly (carrier lens vision). Bioptic lens users can be taught
to use functional visual acuity measures (with and without
telescopic magnification). 27
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Functional visual acuity measures Awareness acuity I notice
something ahead but cant identify what it is (gross difference
between foreground and background) Identification acuity It is
beginning to look like a red vehicle (as driver gets closer to
object) Sure acuity I definitely recognize it as a red car (at
furthest yet optimal viewing distance)
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Awareness acuity 29
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Awareness acuity 30
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Identification acuity 31
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Sure acuity 32
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Misconception No. 3 A low vision driver, who is dipping down
into the telescopic portion of their bioptic lens system every few
seconds or so, is illustrating safe driving practices. 33
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In reality Driving is a dynamic task that requires far greater
input from the peripheral or side portion of ones field of view. If
you cant drive without it, you cant drive with it. 34
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Why use the telescopic unit? At critical periods to increase
ones margin of safety Margin of safety defined as - the time or
distance needed to detect and react to a critical object or
situation 35
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Unexpected road closure! 36
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Misconception No. 4 Low vision drivers need not use bioptics
while driving in familiar driving environments.
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In reality Drivers have no control over anything that takes
place outside of their vehicles - First in line at traffic light
(multi-lane crossroad) - Flagger @ road repaving site, water line
breaks, tree trimming - First responder(s) at scene of motor
vehicle accident 38
