Blue-Light Filtering Spectacle Lenses: Optical and Clinical Performances

Abstract

Purposes: To evaluate the optical performance of blue-light filtering spectacle lenses and investigate whether a reduction in blue light transmission affects visual performance and sleep quality.

Methods: Experiment 1: The relative changes in phototoxicity, scotopic sensitivity, and melatonin suppression of five blue-light filtering plano spectacle lenses were calculated based on their spectral transmittances measured by a spectrophotometer. Experiment 2: A pseudo-randomized controlled study was conducted to evaluate the clinical performance of two blue-light filtering spectacle lenses (BF: blue-filtering anti-reflection coating; BT: brown-tinted) with a regular clear lens (AR) serving as a control. A total of eighty computer users were recruited from two age cohorts (young adults: 18-30 yrs, middle-aged adults: 40-55 yrs). Contrast sensitivity under standard and glare conditions, and colour discrimination were measured using standard clinical tests. After one month of lens wear, subjective ratings of lens performance were collected by questionnaire.

Results: All tested blue-light filtering spectacle lenses theoretically reduced the calculated phototoxicity by 10.6% to 23.6%. Although use of the blue-light filters also decreased scotopic sensitivity by 2.4% to 9.6%, and melatonin suppression by 5.8% to 15.0%, over 70% of the participants could not detect these optical changes. Our clinical tests revealed no significant decrease in contrast sensitivity either with (95% confidence intervals [CI]: AR-BT [-0.05, 0.05]; AR-BF [-0.05, 0.06]; BT-BF [-0.06, 0.06]) or without glare (95% CI: AR-BT [-0.01, 0.03]; AR-BF [-0.01, 0.03]; BT-BF [-0.02, 0.02]) and colour discrimination (95% CI: AR-BT [-9.07, 1.02]; AR-BF [-7.06, 4.46]; BT-BF [-3.12, 8.57]).

Conclusion: Blue-light filtering spectacle lenses can partially filter high-energy short-wavelength light without substantially degrading visual performance and sleep quality. These lenses may serve as a supplementary option for protecting the retina from potential blue-light hazard.

Trial registration: ClinicalTrials.gov NCT02821403.

Conflict of interest statement

Financial support for research: Salary for a research assistant, blue-light filtering spectacle lenses. Employment: The research assistant was employed by Hong Kong PolyU; None of the authors/ research personal was employed by the company. Consultancy: Part of the funding was charged as consulting fee Stocks, shares or ownership of company: None. Patents: None. Products in development: None. Marketed products: None. Royalties: None. We confirm that this does not alter our adherence to PLOS ONE policies on sharing data and materials.

Figures

Fig 1. The flowchart for this pseudo-randomized controlled clinical trial.

Fig 2

The spectral transmittance (a), front surface reflectance (b), phototoxicity (c), scotopic sensitivity (d), and melatonin suppression (e) as a function of wavelength for the five blue-light filtering spectacle lenses. The standard action spectrum curves for the blue-light hazard, scotopic luminous efficiency and circadian efficiency are displayed as dashed lines. The data are summarized in the table at the bottom right.

Fig 3. Log contrast sensitivity scores (mean ±SE) in normal (left) and glare conditions (right) when wearing different tinted lenses in young and middle-aged adults.

AR, white bars. BF, blue bars. BT, yellow bars. There was a significant difference in contrast sensitivity under the no-glare condition between the two age groups: *** p

Fig 4. Total error scores (mean ±SE) when wearing different tinted lenses in young and middle-aged adults.

AR, white bars. BF, blue bars. BT, yellow bars. There was a significant difference in total error scores between the two age groups: *** p

Fig 5. Participants’ preference of lens type in young and middle-aged adults.

AR, white bars. BF, blue bars. BT, yellow bars.

Fig 6. The proportions of participants showing “improvement”, “no change” and “decline” in lens performance when wearing BF (left) and BT (right) lenses.

The arrows indicate questionnaire items showing significantly diverse responses for each item (One-sample Chi-square test, all p<0.05). The colours of the arrows denote the response that contributed most to the Chi-square test (i.e., highest mini-X2). For example, upward black arrows indicate that the diverse responses revealed in Chi-square tests were due to high proportions of “no change”; downward green and red arrows indicate that the diverse responses were due to low proportions of “improvement” and “decline”, respectively.