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Fernando Vargas-Martin; A free-cost visual field expander for peripheral vision loss. Journal of Vision 2003;3(12):40. doi: https://doi.org/10.1167/3.12.40.
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© ARVO (1962-2015); The Authors (2016-present)
Reversed Galilean telescopes have been used for rehabilitation of peripheral visual field loss and are commercially available with a magnification up to ×0.5. A more cost effective visual field expander is constructed by making very minor modifications to off-the-shelf photographic viewfinders from cheap, disposable cameras. These devices can be mounted as spectacles either centrally or peripherally (e.g. bioptic). Optical properties are analyzed objectively with a high resolution web cam. Additionally, expansion of the visual field in subjects is demonstrated by perimetry. Several different types of viewfinders were tested although most of the viewfinders used in this study had a 20 degree field of view with ×0.5 magnification. Comments on the ease of using the visual field expander as well as the advantages and disadvantages between different types of viewfinders are presented. Since creating low cost devices is one of the major goals in low vision aid design (especially in underdeveloped countries), the proposed viewfinders could be a cheaper and more practical solution for visual field expanders.
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