Improvement or Worsening of Human Contrast Sensitivity Due to Blue Light Attenuation at 450 nm

Silvia Tavazzi; Federica Cozza; Gabriele Nigrotti; Chiara Braga; Natalia Vlasak; Silvano Larcher; Fabrizio Zeri

doi:10.2147/OPTO.S242818

Improvement or Worsening of Human Contrast Sensitivity Due to Blue Light Attenuation at 450 nm

Clin Optom (Auckl). 2020 Apr 1:12:57-66. doi: 10.2147/OPTO.S242818. eCollection 2020.

Authors

Silvia Tavazzi^{1

2}, Federica Cozza^{1

2}, Gabriele Nigrotti², Chiara Braga², Natalia Vlasak³, Silvano Larcher⁴, Fabrizio Zeri^{1

2

5}

Affiliations

¹ Department of Materials Science, University of Milano Bicocca, Milan, Italy.
² Research Centre in Optics and Optometry (COMiB), University of Milano Bicocca, Milan, Italy.
³ Hoya Vision Care, Amsterdam, the Netherlands.
⁴ Hoya Lens Italy, Milan, Italy.
⁵ Ophthalmic Research Group, School of Life and Health Sciences, Aston University, Birmingham, UK.

Abstract

Purpose: The work was aimed at comparing contrast sensitivity performance in an indoor environment with two filters, which differ only in the presence of a band at 450±20 nm in the transmittance spectrum.

Patients and methods: Thirty-nine subjects participated. The filters were the Standard (ST) and Professional (PRO) Drive lenses (Hoya, Japan), the latter showing the attenuation band at 450 nm. Photopic contrast sensitivity (CS) was measured at different spatial frequencies from 1.5 to 18 cpd through Functional Acuity Contrast Test with both lenses (LogCS_ST and LogCS_PRO, respectively). The areas under the curves of LogCS_ST and LogCS_PRO as a function of the spatial frequency were also considered.

Results: In the range of the measured values of LogCS_ST for the thirty-nine participants, at each spatial frequency and also for the areas, the difference Δ = LogCS_PRO - LogCS_ST was found to decrease and change sign from positive to negative as a function of LogCS_ST, thus allowing to deduce a threshold (LogCS_threshold) for LogCS_ST corresponding to Δ=0. Significant CS worsening was found with the PRO compared to the ST lens for the subjects showing LogCS_ST > LogCS_threshold. Vice versa, CS improvement was found when LogCS_ST < LogCS_threshold.

Conclusion: In the choice of a blue-filtering lens, practitioners should take into consideration that the attenuation of light in the range 420-470 nm is expected to produce a CS worsening in subjects showing a relatively high initial CS (higher than a threshold CS). For these subjects, the general reduction of transmitted light intensity prevails on possible advantages. On the contrary, subjects showing a relatively low initial CS are expected to show a CS improvement because the attenuation of light in the range 420-470 nm is expected to reduce intraocular scattering and to mimic the effect as an optical filter of the human macular pigment, advantages which prevail on the reduction of the transmitted light intensity.

Keywords: blue filtering; intraocular scattering; macular pigment; optics and spectroscopy; optometry practice.