Objective measurement of forward-scattered light in the human eye: An electrophysiological approach

PLoS One. 2019 Apr 4;14(4):e0214850. doi: 10.1371/journal.pone.0214850. eCollection 2019.

Abstract

Purpose: Psychophysical measurements are used to examine the perception of ocular stray light, for example, with C-Quant. These measurements are subjective due to their principles. This work aims to determine ocular stray light objectively; thus, a psychophysical method is transferred into an electrophysiological setup.

Methods: Stray light perception was measured using steady-state visual evoked potentials (VEPs) in 10 healthy subjects (7 males, 3 females, mean age ± SD: 29.6 ± 4.1 years). Stray light emulating filters (Tiffen Black Pro Mist 2) were used for simulating the effect of cataracts to validate the results for increased scattered light conditions. Based on the direct compensation method, the stimulus consisted of a central test field (radius = 2°) with a luminance adjustable compensation light and surrounding ring-shaped stray light source (radius = 5 to 10°). Both flickered in the counter phase at a frequency of 7.5 Hz. The stimuli were presented for 15 luminance levels of the compensation light. The recorded steady-state VEPs at Oz channel were transformed by means of Fourier analysis. The magnitudes at the evoked frequency were plotted against the measured brightness levels of the compensation light. By fitting two linear functions to the resulting data points, a robust minimum log(Leq) was determined, which was correlated with the amount of stray light perception. We measured the stray light parameter log(sc) using C-Quant. For comparison, our results were converted into the C-Quant equivalent parameter log(sepm) and paired t-tests were performed for normal distributed results.

Results: A significant difference is observed between log(sepm) (without filter) and log(sepm) (with BPM 2 Filter) (p>0.05). No significant difference is observed between log(sepm) (without filter) and log(sc) (without filter) (p > 0.05) and between log(sepm) (with BPM 2 filter) and log(sc) (with BPM 2 filter) (p > 0.05).

Conclusion: The electrophysiological approach offers the ability to measure stray light perception in an objective manner.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Electroencephalography
  • Electrophysiological Phenomena
  • Evoked Potentials, Visual / physiology*
  • Female
  • Humans
  • Light
  • Male
  • Ocular Physiological Phenomena
  • Photic Stimulation
  • Psychophysics
  • Scattering, Radiation
  • Vision, Ocular / physiology*
  • Young Adult

Grants and funding

The authors gratefully acknowledge funding from the German Federal Ministry of Education and Research (Grant 3IPT605X, www.bmbf.de) and the Carl-Zeiss-Foundation (www.carl-zeiss-stiftung.de). We acknowledge support for the Article Processing Charge by the German Research Foundation (DFG) and the Open Access Publication Fund of the Technische Universität Ilmenau. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.