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Optical Engineering • Open Access

Impact of high power and angle of incidence on prism corrections for visual field loss

Paper Abstract

Prism distortions and spurious reflections are not usually considered when prescribing prisms to compensate for visual field loss due to homonymous hemianopia. Distortions and reflections in the high-power Fresnel prisms used in peripheral prism placement can be considerable, and the simplifying assumption that prism deflection power is independent of angle of incidence into the prisms results in substantial errors. We analyze the effects of high prism power and incidence angle on the field expansion, size of the apical scotomas, and image compression/expansion. We analyze and illustrate the effects of reflections within the Fresnel prisms, primarily due to reflections at the bases, and secondarily due to surface reflections. The strength and location of these effects differs materially depending on whether the serrated prismatic surface is placed toward or away from the eye, and this affects the contribution of the reflections to visual confusion, diplopia, false alarms, and loss of contrast. We conclude with suggestions for controlling and mitigating these effects in clinical practice.

Paper Details

Date Published: 17 January 2014
PDF: 14 pages
Opt. Eng. 53(6) 061707 doi: 10.1117/1.OE.53.6.061707
Published in: Optical Engineering Volume 53, Issue 6
Show Author Affiliations
Jae-Hyun Jung, Harvard Medical School (United States)
Eliezer Peli, Harvard Medical School (United States)


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