Acquired monocular vision (AMV) is a common visual field loss. Patients report mobility difficulties in walking due to collisions with objects or other pedestrians on the blind side.
The visual field of people with AMV extends more than 90° temporally on the side of the seeing eye but is restricted to approximately 55° nasally. We developed a novel field expansion device using a multiplexing prism (MxP) that superimposes the see-through and shifted views for true field expansion without apical scotoma. We present various designs of the device that enable customized fitting and improved cosmetics.
A partial MxP segment is attached (base-in) near the nose bridge. To avoid total internal reflection due to the high angle of incidence at nasal field end (55°), we fit the MxP with serrations facing the eye and tilt the prism base toward the nose. We calculated the width of the MxP (the apex location) needed to prevent apical scotoma and monocular diplopia. We also consider the effect of spectacle prescriptions on these settings. The results are verified perimetrically.
We documented the effectivity of various prototype glasses designs with perimetric measurements. With the prototypes, all patients with AMV had field-of-view expansions up to 90° nasally without any loss of seeing field.
The novel and properly mounted MxP in glasses has the potential for meaningful field-of-view expansion up to the size of normal binocular vision in cosmetically acceptable form.
1Schepens Eye Research Institute, Massachusetts Eye and Ear, Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts *email@example.com
Supplemental Digital Content: Appendix A: Critical angle of incidence with 50% transmittance and its effective prism power in various prism powers are analyzed in Appendix, available at (http://links.lww.com/OPX/A355).
Submitted: January 30, 2018
Accepted: June 30, 2018
Funding/Support: National Institutes of Health (R01EY023385 to EP); National Institutes of Health (P30EY003790); and Alice Adler Fellowship from Harvard Medical School (to J-HJ).
Conflict of Interest Disclosure: EP has a patent for the multiplexing prism and its applications, assigned to the Schepens Eye Research Institute and licensed to Chadwick Optical.
Author Contributions and Acknowledgments: Conceptualization: J-HJ, EP; Data Curation: J-HJ; Formal Analysis: J-HJ; Funding Acquisition: EP; Investigation: J-HJ, EP; Methodology: J-HJ, EP; Project Administration: J-HJ, EP; Resources: J-HJ, EP; Software: J-HJ; Supervision: J-HJ, EP; Validation: J-HJ, EP; Visualization: J-HJ; Writing – Original Draft: J-HJ; Writing – Review & Editing: J-HJ, EP.
The authors thank Chadwick Optical for helping with the manufacturing of multiplexing prisms and attaching them to spectacle frames.
Supplemental Digital Content: Direct URL links are provided within the text.