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Functional Fields of BiOptic Telescopes: Implications for Driving. Eli Peli, M.Sc., O.D. Professor of Ophthalmology. Acknowledgements. Russell Woods Ivonne Fetchenheuer . Supported in part by NIH grant #EY12890. Keplerian Vs. Galilean Vignetting Ring scotoma Image shift Simulvision

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functional fields of bioptic telescopes implications for driving

Functional Fieldsof BiOptic Telescopes:Implications for Driving

Eli Peli, M.Sc., O.D.

Professor of Ophthalmology

acknowledgements
Acknowledgements
  • Russell Woods
  • Ivonne Fetchenheuer

Supported in part by NIH grant #EY12890

slide3
Keplerian Vs. Galilean
  • Vignetting
  • Ring scotoma
  • Image shift
  • Simulvision
  • Binocular fields
  • Central field loss
  • Adaptation
bioptic telescope categories
Small, light weight

Narrower field

Exit pupil inside Tx

Head movement

Micro Tx

Eye movement

Bioptic Telescope:Categories

Galilean

DVI 3.0X

BITA 6.0X

bioptic telescope categories5
Larger, heavier

Image erecting system

Wider field of view

Exit pupil behind Tx

Head movement

Eye movement (BTL)

Bioptic Telescope:Categories

Keplerian

DVI 4.0X

Ocuthech VES 4.0X

telescopes tested
Keplerian

4.0X EFT DVI

3.0X Ocutech Mini

4.0X Ocutech VES

3.0X BTL

Galilean

BITA

2.5X, 3.0X and 6.0X

3.0X DVI

Telescopes Tested
field of view of a telescope

obj

ocu

obj’

e

d

L

Field-of-View of a Telescope

Based on

pinhole pupil

FVM

FoV = Retinal Field-of-View

Object Field-of-View = FoV/M

field of view of a galilean

obj

ocu

obj’

e

d

L

Field-of-View of a Galilean

Illustrated for

M = 3.0

expanding the field of a galilean

obj

ocu

obj’

e

d

L

Expanding the field of a Galilean

By moving the telescope closer to the eye

Dangerous?

field of view of a keplerian

obj

ocu

e

L

obj’

d

Field-of-View of a Keplerian

Reminder: based on pinhole pupil

What happened when we open the pupil?

half luminance fov

obj

ocu

Half Luminance FoV

Additional Field is imaged through less than ½ the pupil

Full Luminance FoV

slide13

Monocular Visual Field Extent

40 mm (137 minarc)

5 mm (17 minarc)

1 mm (3.4 minarc)

at 1m

Binocular visual field

+90 deg

slide14

Binocular visual field extent

Right eye

Left eye

Binocular

slide15

Scotoma(ta) in the Visual Fields

Scotoma

  • Absolute
  • Relative
slide16
Keplerian Vs. Galilean
  • Vignetting
  • Ring scotoma
  • Image shift
  • Simulvision
  • Binocular fields
  • Central field loss
  • Adaptation
vignetting
Galilean

Fading away at edge

Reduced light transmission

Isopters are shifted

Poorer optical quality

Vignetting

DVI 3.0X

vignetting18
Keplerian

Inherently wider Field

Can be limited to reduce vignetting

Isopters collapse

Vignetting

4.0X EFT DVI

slide19
Keplerian Vs. Galilean
  • Vignetting
  • Ring scotoma
  • Image shift
  • Simulvision
  • Binocular fields
  • Central field loss
  • Adaptation
ring scotoma

90

10

180

0

7

12

11.5

12

270

Ring Scotoma

Jose & Ousley, 1984

what causes the ring scotoma
What Causes the Ring Scotoma?
  • “..exists because the lenses subtend a greater angle at the eye than the angular size of the of the optical field of view through the telescope.
    • The angular width of the ring scotoma is equal to half the angular size of the objective lens at the eye minus half the angular size of the optical field of view.” (true if ocular at the eye)
    • Feinbloom, 1977.
  • “The physical housing of the telescope”
    • Taylor (1990), citing Fonda (1986)
what causes the ring scotoma22
What Causes the Ring Scotoma?
  • “The rim of the telescopic portion (of the bioptic spectacle) creates a ring-shaped...”
    • Corn, 1990
  • “There is a ring scotoma caused by the edge of the telescope extending…”
    • Lippmann, et al, 1988
  • The ring around the bioptic telescope creates a scotoma or a blind spot that will affect peripheral (side) vision.”
    • Gottlieb et al, 1996
what causes the ring scotoma23
What Causes the Ring Scotoma?
  • “Although both magnified and unmagnified fields can be viewed simultaneously, the telescope housing creates a considerable ring scotoma around the magnified zone.”
    • Christine Dickinson, 1998
  • “A ring scotoma is a blind area in the visual field produced by the housing of the telescope.”
    • Your Guide to Prescribing and Fitting Spectacle-Mounted Telescopes. The Lighthouse Driving Kit, Lighthouse International, 2003
slide24

45 degree field

What Causes the Ring Scotoma?

slide25

Magnification CausesRing Scotoma

No structure effect needed

ring scotoma26
Ring Scotoma

3.0 DVI

  • Can be measured with perimeter
  • Note, shift of physiological scotoma and asymmetric ring scotoma
when you really don t like bioptic
When you really don’t like BiOptic!

6°3.0 = 18°

Measuredscotoma

28° ?

slide29

90

10

180

0

7

12

11.5

12

270

Jose & Ousley, 1984

slide30

Superior & Inferior Fields

  • with 3x EFTs
          • Car Hood 80 cm High
          • Driver 120 cm High
          • Eye To Hood Distance 210 cm
          • Eye To Hood Angle 10.8
          • With 4.8 Tilt Down

200

150

100

50

Height (Cm)

4.2 M

11.6 M

Jose & Ousley, 1984

slide31

Visual Field & Scotoma with 3x EFTs on 6.1 Meter Road Assuming 12

9176

61

46

30

15

0

15

30

46

61

76

57.7 M

38.4 M

19.2 M

NASAL FIELD METERS TEMPORAL FIELD

9.6 M

19.2 M

28.8 M

11.5 M

23 M

34.5 M

30 61 91 122 152 183 213 244 274 305

Jose & Ousley, 1984

Why is it asymmetric?

slide32
Keplerian Vs. Galilean
  • Vignetting
  • Ring scotoma
  • Image shift
  • Simulvision
  • Binocular fields
  • Central field loss
  • Adaptation
image shift in telescope
Image shift in telescope
  • Caused by axial misalignment
  • Consequences?
    • Possible benefit
      • Control image position
ring scotoma with tx
Ring Scotoma with Tx

3.0X DVI Bioptic

fitting the telescope
Ideal alignment:

eye to center of leveled telescope

Fitting the telescope

Tilt head up ~10º to be leveled

Telescope blocks the view of leveled eye

Further head tilt is neededto clear the view

measured head tilt
Needed to move from viewing through the telescope to viewing through the carrier lens

All much larger than 10 degrees

Some uncomfortably large

Measured Head Tilt
fitting the telescope37
Another AproachFitting the telescope

Start with a 10º mounted telescope.

Head leveled. Move telescope up to clear the view under telescope

A 10º head tilt levels the telescope.

Eye is not centered on telescope

Results in image shift

fitting the telescope38
Real

Recent Illustration

Fitting the telescope

Ocutech

consequences of image shift
Consequences of Image Shift?
  • Shift of physiological scotoma
  • Shift of magnified image
  • Possibility to control the position of Ring Scotoma
slide40
Keplerian Vs. Galilean
  • Vignetting
  • Ring scotoma
  • Image shift
  • Simulvision
  • Binocular fields
  • Central field loss
  • Adaptation
bita telescope simulvision
BITA telescope SimulVision

Spatial Multiplexing

bita simulvision
BITA SimulVision
  • Shifted magnification scotoma
  • Shifted physiological scotoma
  • Caused by lens tilt
in the lens telescope
In-the-Lens Telescope

Better Cosmesis

Unimpeded Eye Contact

slide45

t

t

In-the-Lens Telescope

Shifting of Scotoma

Front View

Side View

slide48
Keplerian Vs. Galilean
  • Vignetting
  • Ring scotoma
  • Image shift
  • Simulvision
  • Binocular fields
  • Central field loss
  • Adaptation
monocular bioptic telescope
Monocular Bioptic Telescope

Bi-ocular Multiplexing

binocular fields with monocular tx
Binocular Fields with Monocular Tx
  • “Drivers with a bioptic telescope before only one eye have no significant loss of functional visual field.” (Feinbloom, 1977)
  • “Simple confrontation experiment, however, verify that objects obscured by BTS ring scotoma can be perceived within the field of the naked eye while the BTS- fitted eye fixates.” (Lippmann, et al, 1988)
binocular fields with monocular tx51
Binocular Fields with Monocular Tx
  • “When tested on a Goldman Perimeter with both eyes open a scotoma of any kind can not be plotted.” (Jose & Ousley, 1984)
binocular field with monocular tx
Binocular field with Monocular Tx

Normally Sighted

4.0 DVI, OD

Real World?

binocular visual fields
Most ConventionalHLP-VESBinocular Visual Fields

BITA & BTL no binocular scotomata

slide55
Keplerian Vs,. Galilean
  • Vignetting
  • Ring scotoma
  • Image shift
  • Simulvision
  • Binocular fields
  • Central field loss
  • Adaptation
impact of central field loss
Impact of central field loss

Subject RP (JMD, right: 20/175, left: 20/225)

Monocular, OD

Binocular

OD & OS

Monocular Fields

With Monocular Telescope

binocular fields with monocular tx57
Binocular fields with monocular Tx
  • “When tested on a Goldman Perimeter with both eyes open a scotoma of any kind can not be plotted.” (Jose & Ousley, 1984)
impact of central field loss58
Impact of central field loss

Subject PJ (JMD, right: 20/250, left: 20/400)

Monocular, OD

Binocular

With Monocular Telescope

OD/OS

impact of central field loss59
Impact of central field loss

Subject RG (Cone- Rod Dystrophy, right 20/200, left 20/200)

Monocular, OD

Binocular

OD/OS

With Monocular Telescope

slide60
Keplerian Vs,. Galilean
  • Vignetting
  • Ring scotoma
  • Image shift
  • Simulvision
  • Binocular fields
  • Central field loss
  • Adaptation
initial response of visually impaired users
Initial Responseof Visually Impaired Users

Naïve Users

  • PJ: intermittently suppressed fellow eye
  • RG: intermittently suppressed fellow eye
  • CN: suppressed magnified image
  • BE: no suppression
initial response of visually impaired users62
Initial Responseof Visually Impaired Users

Experienced bioptic users

  • RP: no suppression
  • BR: suppressed fellow eye in magnified field

Simple visual environment

Real world?

conclusions
Conclusions
  • People without CFL can have scotomata in binocular visual field
  • CFL usually causes scotomata in binocular visual field
  • People with CFL may suppressed one eye when viewing through monocular telescope
  • Scotomata can be shifted/controlled
recommendations
Recommendations
  • Visual field measurements can help assess bioptic wearers potential for effective use in mobility (driving) and monitor the state of suppression
  • Studies are needed to determine the usefulness of the other eye‘s view in driving
  • Blocking fellow eye‘s view may help in initial training
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