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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

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Functional fields of bioptic telescopes implications for driving l.jpg

Functional Fieldsof BiOptic Telescopes:Implications for Driving

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

Professor of Ophthalmology


Acknowledgements l.jpg

Acknowledgements

  • Russell Woods

  • Ivonne Fetchenheuer

Supported in part by NIH grant #EY12890


Slide3 l.jpg

  • Keplerian Vs. Galilean

  • Vignetting

  • Ring scotoma

  • Image shift

  • Simulvision

  • Binocular fields

  • Central field loss

  • Adaptation


Bioptic telescope categories l.jpg

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 l.jpg

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 l.jpg

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 l.jpg

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 l.jpg

obj

ocu

obj’

e

d

L

Field-of-View of a Galilean

Illustrated for

M = 3.0


Expanding the field of a galilean l.jpg

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 l.jpg

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 l.jpg

obj

ocu

Half Luminance FoV

Additional Field is imaged through less than ½ the pupil

Full Luminance FoV


How does the field of view of the telescope interact with the visual field of the user l.jpg

Functional Fields

How does the Field-of-View of the Telescope Interact with the Visual Field of the User?


Slide13 l.jpg

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 l.jpg

Binocular visual field extent

Right eye

Left eye

Binocular


Slide15 l.jpg

Scotoma(ta) in the Visual Fields

Scotoma

  • Absolute

  • Relative


Slide16 l.jpg

  • Keplerian Vs. Galilean

  • Vignetting

  • Ring scotoma

  • Image shift

  • Simulvision

  • Binocular fields

  • Central field loss

  • Adaptation


Vignetting l.jpg

Galilean

Fading away at edge

Reduced light transmission

Isopters are shifted

Poorer optical quality

Vignetting

DVI 3.0X


Vignetting18 l.jpg

Keplerian

Inherently wider Field

Can be limited to reduce vignetting

Isopters collapse

Vignetting

4.0X EFT DVI


Slide19 l.jpg

  • Keplerian Vs. Galilean

  • Vignetting

  • Ring scotoma

  • Image shift

  • Simulvision

  • Binocular fields

  • Central field loss

  • Adaptation


Ring scotoma l.jpg

90

10

180

0

7

12

11.5

12

270

Ring Scotoma

Jose & Ousley, 1984


What causes the ring scotoma l.jpg

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 l.jpg

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 l.jpg

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 l.jpg

45 degree field

What Causes the Ring Scotoma?


Slide25 l.jpg

Magnification CausesRing Scotoma

No structure effect needed


Ring scotoma26 l.jpg

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 l.jpg

When you really don’t like BiOptic!

6°3.0 = 18°

Measuredscotoma

28° ?


Slide29 l.jpg

90

10

180

0

7

12

11.5

12

270

Jose & Ousley, 1984


Slide30 l.jpg

  • 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 l.jpg

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 FIELDMETERS 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 l.jpg

  • Keplerian Vs. Galilean

  • Vignetting

  • Ring scotoma

  • Image shift

  • Simulvision

  • Binocular fields

  • Central field loss

  • Adaptation


Image shift in telescope l.jpg

Image shift in telescope

  • Caused by axial misalignment

  • Consequences?

    • Possible benefit

      • Control image position


Ring scotoma with tx l.jpg

Ring Scotoma with Tx

3.0X DVI Bioptic


Fitting the telescope l.jpg

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 l.jpg

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 l.jpg

Another Aproach

Fitting 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 l.jpg

Real

Recent Illustration

Fitting the telescope

Ocutech


Consequences of image shift l.jpg

Consequences of Image Shift?

  • Shift ofphysiological scotoma

  • Shift of magnified image

  • Possibility to control the position of Ring Scotoma


Slide40 l.jpg

  • Keplerian Vs. Galilean

  • Vignetting

  • Ring scotoma

  • Image shift

  • Simulvision

  • Binocular fields

  • Central field loss

  • Adaptation


Bita telescope simulvision l.jpg

BITA telescope SimulVision

Spatial Multiplexing


Bita simulvision l.jpg

BITA SimulVision

  • Shifted magnification scotoma

  • Shifted physiological scotoma

  • Caused by lens tilt


Magnification scotoma shifted down l.jpg

Magnification Scotoma Shifted Down

  • Behind-the-lens Tx


In the lens telescope l.jpg

In-the-Lens Telescope

Better Cosmesis

Unimpeded Eye Contact


Slide45 l.jpg

t

t

In-the-Lens Telescope

Shifting of Scotoma

Front View

Side View


Slide48 l.jpg

  • Keplerian Vs. Galilean

  • Vignetting

  • Ring scotoma

  • Image shift

  • Simulvision

  • Binocular fields

  • Central field loss

  • Adaptation


Monocular bioptic telescope l.jpg

Monocular Bioptic Telescope

Bi-ocular Multiplexing


Binocular fields with monocular tx l.jpg

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 l.jpg

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 l.jpg

Binocular field with Monocular Tx

Normally Sighted

4.0 DVI, OD

Real World?


Ocutech horizontal telescope manual or auto focus l.jpg

Ocutech Horizontal TelescopeManual or Auto focus


Binocular visual fields l.jpg

Most ConventionalHLP-VES

Binocular Visual Fields

BITA & BTL no binocular scotomata


Slide55 l.jpg

  • Keplerian Vs,. Galilean

  • Vignetting

  • Ring scotoma

  • Image shift

  • Simulvision

  • Binocular fields

  • Central field loss

  • Adaptation


Impact of central field loss l.jpg

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 l.jpg

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 l.jpg

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 l.jpg

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 l.jpg

  • Keplerian Vs,. Galilean

  • Vignetting

  • Ring scotoma

  • Image shift

  • Simulvision

  • Binocular fields

  • Central field loss

  • Adaptation


Initial response of visually impaired users l.jpg

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 l.jpg

Initial Responseof Visually Impaired Users

Experienced bioptic users

  • RP: no suppression

  • BR: suppressed fellow eye in magnified field

    Simple visual environment

    Real world?


Conclusions l.jpg

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 l.jpg

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


Thank you l.jpg

Thank You!


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