Multiplexing prism for field expansion of acquired ...

Multiplexing prism for field expansion of acquired monocular vision & normal sight

Jae-Hyun Jung and Eli Peli Schepens Eye Research Institute, Massachusetts Eye and Ear, Harvard Medical School, Boston, MA

Acquired Monocular Vision (AMV)

Field expansion devices for AMV

Multiplexing Prism (MxP)

? Loss of an eye or loss of sight of one eye is frequently due to injury and it affects the daily life significantly1,2

? The loss of visual field on one side has no effective solution currently

? The retina areas blocked by the nose, do not function visually

Monocular visual field

Field with nose pAripsmical scotoma

The National Institute of Rehabilitation Engineering (NIRE), CROS-VISION 1

Monocular

visual field (-90? ~ 58 ?)

Mirror on walking cane

Reflected visual field

CROS-VISION ? NIRE(1980s)3 Very minimal expansion (3? to 7?), apical scotoma

Field expansion device based on mirror (2013)2 Rear view but not a side view It may be rearranged to provide some side view. The field covered by such mirror is tiny-not helpful.

? A device that provides simultaneous shifted and unshifted (i.e., multiplexed) views The MxP alternates flat areas between the prismatic segments

? Apical scotoma: The prism extends the field to the prism base, but loses field at its apex.5 MxP eliminates the apical scotoma

Duke Federico da Montefeltro (15C Italian warrior) had

the bridge of his nose removed

One-Eyed Matador

Rotation reduces total internal reflection

Nodal point

Blind eye

Mirror attached to walking cane

Field expansion of AMV rugby player

Apical scotoma (30 base-left)

Concept of multiplexing prism

Photo of perimetry grid taken with 40

multiplexing prism

Field expansion devices for normal peripheral field

? High angle of incidence into prism over the nose bridge causes total internal reflection (TIR)6

? Prism rotation reduces angle - increase the number of effective prism segments

? Nasal field of AMV player to be expanded by multiplexing prism mounted in the approved safety goggle.

Effective prism

segments

Effective prism

segments

Ineffective prism segments

(TIR)

Nodal point

TIR Limits effective prism segments in MxP without rotation

Ineffective prism segments

(TIR)

Nodal point

Prism rotation increases number and area of effective segments

One-eye rugby professional player Leinster's Ian McKinley (Ireland)

IRB (International Rugby Board) Trial Approved Goggle

Cyclops in movie "Percy Jackson: Sea of monster"

Optical correction for a left AMV using MxP

? Mirror, lens, or prism have been used for peripheral field expansion of bicyclists

Spy glasses based on the half mirror on periphery of lens ? Semi silvered mirror device (spy glasses) expands the field but with reversed image and motion

Design proposed on the Internet7 for prism spectacles to provide increased peripheral field for bicyclists (did not address the apical scotoma)

? Lens or prism based devices limited by apical scotoma

? Field substitution Not field expansion

? Multiplexing Fresnel prism over the bridge of the nose in a single lens wrap around sunglasses

? Both expanded visual field by prism shift and see-through visual field (normal visual field) are shown by multiplexing prism

See-through visual field

? Conventional press on prism (40) over the bridge of the nose in the wrap-around sunglasses provide 20? nasal field expansion with apical scotoma

? Field expansion without apical scotoma achieved with a prototype multiplexing prism of 40 in the same position

? Lower contrast due to the multiplexing is expected in the crosshatched area

40 conventional Press on Fresnel prism mounted over the bridge for AMV

Field expansion using Press on prism Field expansion using MxP

with apical scotoma

without apical scotoma

Expanded visual field

Overlap of see-through and expanded visual fields

Contrast reduction

1

Rotated Blind eye MxP Nodal point

Expanding the normal peripheral field

? Multiplexing Fresnel prism on temporal ends of wrap around sunglasses lenses

? Expanded visual field by prism shift and see-through visual field (normal visual field) are both available through the multiplexing prism

See-through visual field

Overlap of see-through and expanded visual fields

See-through visual field

Expanded visual field

Rotated MxP

Rotated MxP

Expanded visual field

? A conventional 40 Fresnel mounted base out on the lateral wing of a safety frame An expansion of about 10? is shown with a corresponding apical scotoma of about 15?

? A segment of multiplexing prism (similar to that used for AMV above) is placed at the same position on the spectacles temple. The peripheral field was expanded by 10? without apical scotoma

? The field was measured using dark targets on a bright background in our PC-based perimeter to avoid false detections of spurious reflections and scattering

Normal monocular visual field

Normal monocular visual field

Conclusion

? Prism segment over the nose bridge expands the nasal visual field

? MxP segment at temporal periphery expands peripheral visual field for bicyclists, motorcyclists

? In both applications, the apical scotoma is a major limitation

? The multiplexing prism overcomes the apical scotoma problem ? At a cost of reduced contrast and monocular visual confusion

? Appropriate rotation of prism segment can reduce total internal reflection It can also increase the expansion of visual field ? Objects in the expanded field are minified

Conventional Fresnel prism (40)

Contrast reduction

Multiplexing prism (40)

Acknowledgement and References

? Supported in part by NIH grants EY12890 and EY023385

? Dr. Peli has patent (application) rights (assigned to Schepens Eye Research Institute) for the Multiplexing prisms

1) Brady, F. B. (1972) A singular view: The art of seeing with one eye, Medical Economics Company, Montvale, New Jersey 2) Slonim, C.B., Martino, A. Z. (2011) Eye was there, AuthorHouse, Bloomington, Indiana 3) National Institute of Rehabilitation Engineering (2006) Cros-Vision Glasses for People Sighted in One Eye, 4) Ihrig, C. (2013) Vision rehabilitation team management of acquired monocular vision, Optometry and Vision Science, 90(3), e89-e94. 5) Apfelbaum, H. L., Ross, N. C., Bowers, A. B., Peli, E.(2013) Considering optical scotomas, confusion, and diplopia when prescribing prisms for homonymous hemianopia, Translational Vision Science & Technology 2(4), article 2 6) Jung, J. -H., Peli, E.(2014) Impact of high power and angle of incidence on prism corrections for visual field loss, Optical Engineering 53(6), 061707, Open Access 7) May, B. (2008)

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