4129-A0117 Multiplexing prism glasses for field expansion in bitemporal hemianopia Jae-Hyun Jung and Eli Peli Schepens Eye Research Institute, Massachusetts Eye and Ear, Harvard Medical School, Boston, MA Peripheral prisms for Homonymous Hemianopia • Peripheral Prisms1,2 (2000) Expand upper and lower segments of the lateral visual field for Homonymous Hemianopia (HH) using Fresnel prisms Multiplexing Prism (MxP) • • OPS and EPS Configurations • • A device that provides simultaneous shifted and unshifted (i.e., multiplexed) views The MxP alternates flat areas between the Fresnel prismatic segments5 EPS Prism rotation reduces TIR • EPS Prism rotation reduces angle of incidence - Increase the number of effective prism segments Outward Prism Serration (OPS): Commonly used for PMMA Fresnel Peli prism Eyeward Prism Serration (EPS): Commonly used for press-on prism Rotation TIR(OPS) Effective prism segments TIR(EPS) Outward Prism Serration (OPS) 57Δ Ineffective prism segments (TIR) 57Δ Apex angle Bitemporal Hemianopia • Bitemporal Hemianopia (BH) results from compromised nasal fibers of the optic nerves in both eyes due to lesion at the optic chiasm3 Left Eye View Concept of multiplexing prism Unseen Seen only by left eye Seen only by right eye See-through view Seen only by left eye Seen only by right eye Shifted view Seen only by left eye Seen only by right eye TIR Limits effective prism segments even in EPS MxP without rotation • • • • Multiplexing Fresnel prism over the bridge of the nose in wrap around sunglasses Expands visual field both by prism shift and prism minification See-through visual field eliminates the apical scotoma Right Eye View • See-through visual field Right Eye Nasal Field Prism rotation increases number and area of effective segments Optical correction for a left acquired monocular vision using MxP Press on prism (40Δ) over the bridge of the nose in the wrap-around sunglasses provide 20° nasal field shift(up to 80° of nasal field) but with apical scotoma Field expansion without apical scotoma achieved with a prototype multiplexing prism of 40Δ in the same position 40Δ Press on Fresnel prism (EPS) mounted over the bridge for AMV Overlap of see-through and expanded visual fields Left Eye Nasal Field Nodal point Eyeward Prism Serration (EPS) Photo of perimetry grid taken through 40∆ multiplexing prism • See-though view of MxP eliminates the apical scotoma • See-through and shifted views split light/contrast Ineffective prism segments (TIR) Nodal point 38Δ Peli Prism glasses Binocular visual field of Visual field expansion Rigid Fresnel Peripheral Prisms a person with HH with 40Δ peripheral prisms Effective prism segments Field expansion using Press on prism with apical scotoma Contrast reduction Nose Expanded visual field Apical scotoma covered by see-through view (50% contrast) Left Eye View Right Eye View Shifted view (50% contrast) Simulated binocular visual field expansion with hypothetical 30° constant deflection power MxP for BH Binocular Field Nasal field expansion by peripheral prism • Temporal retina areas, blocked by the nose, do not function visually • Peripheral prism can expand nasal field of BH • Apical scotoma: Prism extends the field towards the prism base, but loses field at its apex4 Field expansion using MxP without apical scotoma Blind eye Prism Power Variation with Angle of Incidence • Deflection angle of actual prism is highly dependent on the angle of incidence6 • Above a critical angle of incidence, total internal reflection (TIR) Rotated MxP Nodal point Optimize optical correction for BH using MxP • • Expanded visual field of BH using MxP • Two multiplexing Fresnel prism over the bridge of the nose in wrap around sunglasses designed to expand nasal fields in both eyes Parts of expanded visual field of both prism segments may be blocked by the prism segment for the fellow eye • 15° rotated MxP (40Δ) with EPS over the bridge of the nose in a wrap-around sunglasses provide nasal field expansion of both eyes without apical scotoma Nasal field was expanded up to 80° and the interference was almost eliminated Optimized 40Δ PMMA Fresnel prisms mounted over the bridge for BH Deflection angle Expanded binocular field using MxP See-through visual field Expanded visual field TIR Binocular field of patient with BH Angle of incidence Prism view A B Duke Federico da Montefeltro (15C Italian warrior) had the bridge of his nose removed after losing the right eye Apical scotoma (30∆ base-left) - Field interfered by prism segment for the fellow eye + Critical angle of incidence Apical scotoma in peripheral prism • High angle of incidence into prism over the nose bridge causes TIR6 • In HH: The fellow eye covers for apical scotoma • In BH: Apical scotoma is not covered by the fellow eye Unseen Seen only by left eye Seen only by right eye Unseen Seen only by left eye Seen only by right eye See-through view Seen only by left eye Seen only by right eye 40° 56° • • Expanded visual field See-through visual field Nose Apical scotoma Simulated binocular visual field expansion with 30° constant deflection power for BH Apical scotoma covered by see-through view (50% intensity) • • • • • Expanded visual field Apical scotoma covered by right eye Simulated binocular visual field expansion with 30° constant deflection power for left HH • The interference from fellow eye segment is prevented by using lower power of prism and adjusting rotation angle and segment size Conclusion and References No field expansion Shifted view was lost to total internal reflection Simulated binocular visual field expansion with real 57Δ (30° nominal power) peripheral prisms for BH 56° 83° 15° rotation of EPS MxP Prism segments over the nose bridge expand the nasal visual field for BH & AMV Nasal prism for BH is affected by apical scotoma The multiplexing prism overcomes the apical scotoma – At a cost of reduced contrast and monocular visual confusion Appropriate rotation of prism in EPS configuration reduces TIR Optimized rotation angle and size with lower power of prism is required to minimize this interference and maximize the expansion Supported in part by NIH grants EY12890 and EY023385 Dr. Peli has patent application rights (assigned to Schepens) for the MxP 1) E. Peli (2000), Field expansion for homonymous hemianopia by optically-induced peripheral exotropia, Optometry and Vision Science, 77(9), 453-464 2) E. Peli (2008), Peripheral Field Expansion Device, United States patent 7,374,284 3) E. Peli, P. Satgunam P. (2014), Bitemporal hemianopia; its unique binocular complexities and a novel remedy, Ophthalmic and Physiological Optics; 34: 233–242 4) H. L. Apfelbaum, N. C. Ross, A. B. Bowers, E. Peli (2013), Considering optical scotomas, confusion, and diplopia when prescribing prisms for homonymous hemianopia, Translational Vision Science & Technology 2(4), article 2 Open Access 5) J.-H. Jung, E. Peli (2014), Multiplexing prism for field expansion of acquired monocular vision and normal sight, Poster presented at the Vision 2014 conference, Melbourne, Australia 6) J.-H. Jung, E. Peli, (2014), Impact of high power and angle of incidence on prism corrections for visual field loss, Optical Engineering 53(6), 061707, Open Access
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