Design, simulation and evaluation of uniform magnetic field systems for head-free eye movement recordings with scleral search coils.

Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual International Conference · 2016 · Unclear · Insufficient evidence

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UnclearInsufficient evidencePaper 2895

Finite element and numerical simulations of different coil geometries were performed and a 2.2 × 2.2 × 2.2 m coil frame (3 × 4 coils) was built to generate a 3D magnetic field. Measured flux density agreed with simulations, and the system produced a highly un…

Study snapshot

PublicationAnnual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual International Conference · 2016

Study typeengineering

Reported directionUnclear

Evidence ratingInsufficient

Abstract

The precise measurement of eye movements is important for investigating vision, oculomotor control and vestibular function. The magnetic scleral search coil technique is one of the most precise measurement techniques for recording eye movements with very high spatial (≈ 1 arcmin) and temporal (>kHz) resolution. The technique is based on measuring voltage induced in a search coil through a large magnetic field. This search coil is embedded in a contact lens worn by a human subject. The measured voltage is in direct relationship to the orientation of the eye in space. This requires a magnetic field with a high homogeneity in the center, since otherwise the field inhomogeneity would give the false impression of a rotation of the eye due to a translational movement of the head. To circumvent this problem, a bite bar typically restricts head movement to a minimum. However, the need often emerges to precisely record eye movements under natural viewing conditions. To this end, one needs a uniform magnetic field that is uniform over a large area. In this paper, we present the numerical and finite element simulations of the magnetic flux density of different coil geometries that could be used for search coil recordings. Based on the results, we built a 2.2 × 2.2 × 2.2 meter coil frame with a set of 3 × 4 coils to generate a 3D magnetic field and compared the measured flux density with our simulation results. In agreement with simulation results, the system yields a highly uniform field enabling high-resolution recordings of eye movements.

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AI evidence extraction

Structured fields below were generated from the paper’s abstract and metadata to make the evidence easier to inspect. Automated extraction may be incomplete or incorrect; verify important details against the original paper.

Study typeengineering

Effect directionunclear

PopulationHuman subjects (contact lens with embedded search coil mentioned)

Sample sizeNot supplied

ExposureNot supplied

Evidence strengthInsufficientConfidence: 74% · Peer reviewed: yes

Main findings

Outcomes measured

Magnetic field (flux density) homogeneity/uniformity
Agreement between simulated and measured magnetic flux density
Feasibility for high-resolution eye movement recordings under head-free/natural viewing conditions

View raw extracted JSON

{
  "study_type": "engineering",
  "exposure": {
    "band": null,
    "source": "magnetic scleral search coil recording system (coil frame generating 3D magnetic field)",
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": null
  },
  "population": "Human subjects (contact lens with embedded search coil mentioned)",
  "sample_size": null,
  "outcomes": [
    "Magnetic field (flux density) homogeneity/uniformity",
    "Agreement between simulated and measured magnetic flux density",
    "Feasibility for high-resolution eye movement recordings under head-free/natural viewing conditions"
  ],
  "main_findings": "Finite element and numerical simulations of different coil geometries were performed and a 2.2 × 2.2 × 2.2 m coil frame (3 × 4 coils) was built to generate a 3D magnetic field. Measured flux density agreed with simulations, and the system produced a highly uniform field suitable for high-resolution eye movement recordings.",
  "effect_direction": "unclear",
  "limitations": [],
  "evidence_strength": "insufficient",
  "confidence": 0.74,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "scleral search coil",
    "eye movement recording",
    "uniform magnetic field",
    "magnetic flux density",
    "finite element simulation",
    "coil geometry",
    "3D magnetic field",
    "field homogeneity"
  ],
  "suggested_hubs": []
}

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AI-extracted fields are generated from the abstract and metadata and may be incomplete or incorrect. This material is for informational purposes and is not medical advice.

Identifiers and source

DOI: 10.1109/embc.2016.7590686
PubMed: 28268323

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