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Evanescent Field Based Photoacoustics: Optical Property Evaluation at Surfaces
Published on: July 26, 2016
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No Useful Field Expansion with Full-field Prisms.
1Schepens Eye Research Institute, Massachusetts Eye and Ear, Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts *jaehyun_jung@meei.harvard.edu.
Summary
Full-field prisms do not effectively expand the visual field for homonymous hemianopia (HH) or acquired monocular vision (AMV). The necessary head and eye movements to maintain fixation negate any potential visual field expansion benefits.
Area of Science:
- Ophthalmology
- Neuroscience
- Optometry
Background:
- Full-field prisms are investigated for visual field expansion in homonymous hemianopia (HH) and acquired monocular vision (AMV).
- These prisms are also used in treating binocular dysfunction and spatial hemineglect post-brain injury.
Purpose of the Study:
- To evaluate the effectiveness of full-field prisms in expanding the visual field for patients with HH and AMV.
- To determine if prism-induced visual field shifts are beneficial despite compensatory head and eye movements.
Main Methods:
- Meniscus and flat full-field yoked prisms (7Δ and 12Δ) were fitted to participants with HH and AMV.
- Goldmann perimetry was conducted, and results were compared with ray tracing calculations.
Main Results:
- Prism effectiveness was assessed at primary gaze and eccentricities; meniscus prisms maintained consistent power.
- Fixation on targets required head/eye rotation away from the blind side, negating field shifts.
- No significant field expansion was observed in HH; a minor nasal field shift occurred in AMV with flat prisms only.
Conclusions:
- Full-field prisms are ineffective for visual field expansion in HH and AMV due to unavoidable fixation shifts.
- While flat prisms offer a slight field substitution in AMV, they lack refractive correction and provide limited benefit.
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