≡ Menu

Here is an interesting study specifically designed to determine if blue blocking glasses would be helpful for night shift workers. The specific intention was to discover if blue blockers can negate the powerful melatonin suppression of early morning sunlight that workers may be exposed to on the way home from work.


Blocking morning light exposure with dark goggles can contribute to the adjustment to night work but these glasses are incompatible with driving. Recently, it was discovered that the biological clock is most sensitive to short wavelengths (blue light). Therefore, we tested the hypothesis that cutting the blue portion of the light spectrum with orange lens glasses (blue blockers) would prevent the light-induced melatonin suppression, a test broadly used as an indirect assessment of the circadian clock sensitivity. Fourteen normal subjects were exposed at night to a 60 min bright light pulse (1300 lx behind filters) between 01:00 and 02:00 hr while wearing orange lens glasses (experimental condition) or grey lens glasses (control condition). The amount of salivary melatonin change observed during the light pulse was compared with a melatonin baseline obtained the night before. Although both glasses transmitted the same illuminance (1300 lx) but at an irradiance 25% higher for the orange lens (408 microW/cm2) compared with the grey lens (327 microW/cm2), a non-significant increase of 6% (95% CI, -20% to 9%) was observed with the orange lens whereas a significant (P < 0.05) reduction of 46% (95% CI, 35-57%) was observed with the grey lens. Blue blockers represent an elegant means to prevent the light-induced melatonin suppression. Further studies are needed to show that these glasses, which are suitable for driving, could facilitate adaptation to night work.

Overall this is an excellent study. The sample size was small but it was a crossover study which is excellent. Subjects were in a dim room (less than 5 lux) in the evening and then exposed to a “pulse” of light (1300 lux at the eye) for one hour at a set time. The test group wore orange lens glasses. The control wore grey lens glasses. So these people got to relax and watch tv for a while but then the had to stare into a light box for one full hour. Mental note: Never volunteer for a research study.
Melatonin saliva samples were taken at regular intervals. The control group ended up having an average melatonin reduction of 46% while the experimental orange lens group had a negligible effect.

Bottom line: High quality blue blocking glasses prevent light from suppressing melatonin.

Back to Top ↑