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Functional Fields of BiOptic Telescopes: Implications for Driving

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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  1. Functional Fieldsof BiOptic Telescopes:Implications for Driving Eli Peli, M.Sc., O.D. Professor of Ophthalmology

  2. Acknowledgements • Russell Woods • Ivonne Fetchenheuer Supported in part by NIH grant #EY12890

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

  4. 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

  5. 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

  6. 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

  7. 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

  8. obj ocu   obj’ e d L Field-of-View of a Galilean Illustrated for M = 3.0

  9. obj ocu  obj’ e d L Expanding the field of a Galilean By moving the telescope closer to the eye Dangerous?

  10. obj ocu  e L obj’ d Field-of-View of a Keplerian Reminder: based on pinhole pupil What happened when we open the pupil?

  11. obj ocu   Half Luminance FoV Additional Field is imaged through less than ½ the pupil Full Luminance FoV

  12. Functional Fields How does the Field-of-View of the Telescope Interact with the Visual Field of the User?

  13. Monocular Visual Field Extent 40 mm (137 minarc) 5 mm (17 minarc) 1 mm (3.4 minarc) at 1m Binocular visual field +90 deg

  14. Binocular visual field extent Right eye Left eye Binocular

  15. Scotoma(ta) in the Visual Fields Scotoma • Absolute • Relative

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

  17. Galilean Fading away at edge Reduced light transmission Isopters are shifted Poorer optical quality Vignetting DVI 3.0X

  18. Keplerian Inherently wider Field Can be limited to reduce vignetting Isopters collapse Vignetting 4.0X EFT DVI

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

  20. 90 10 180 0 7 12 11.5 12 270 Ring Scotoma Jose & Ousley, 1984

  21. 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)

  22. 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

  23. 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

  24. 45 degree field What Causes the Ring Scotoma?

  25. Magnification CausesRing Scotoma No structure effect needed

  26. Ring Scotoma 3.0 DVI • Can be measured with perimeter • Note, shift of physiological scotoma and asymmetric ring scotoma

  27. When you really don’t like BiOptic! 6°3.0 = 18° Measuredscotoma 28° ?

  28. 90 10 180 0 7 12 11.5 12 270 Jose & Ousley, 1984

  29. 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

  30. 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?

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

  32. Image shift in telescope • Caused by axial misalignment • Consequences? • Possible benefit • Control image position

  33. Ring Scotoma with Tx 3.0X DVI Bioptic

  34. 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

  35. 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

  36. 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

  37. Real Recent Illustration Fitting the telescope Ocutech

  38. Consequences of Image Shift? • Shift of physiological scotoma • Shift of magnified image • Possibility to control the position of Ring Scotoma

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

  40. BITA telescope SimulVision Spatial Multiplexing

  41. BITA SimulVision • Shifted magnification scotoma • Shifted physiological scotoma • Caused by lens tilt

  42. Magnification Scotoma Shifted Down • Behind-the-lens Tx

  43. In-the-Lens Telescope Better Cosmesis Unimpeded Eye Contact

  44. t t In-the-Lens Telescope Shifting of Scotoma Front View Side View

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

  46. Monocular Bioptic Telescope Bi-ocular Multiplexing

  47. 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)

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