How sunglasses work

And why they might be doing you harm

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How do sunglasses actually work? How can they actually cause damage to your eyes? And why are astronauts' sunglasses made of gold? Kate explains all.

Too much light can be a bad thing, and our bodies, with their deep set eyes shielded by bushy brows, are already designed to limit the amount that sneaks in. It is thought that the first sunglasses were made from caribou horns with tiny slits in them that restricted the amount of light entering the eye.

Sunglass design has come a long way since then. Light from the high energy end of the spectrum can cause damage to the body’s cells, by breaking chemical bonds in the molecules such as DNA. 

So how do sunglasses protect you? Light absorbing particles in the glasses block some of the light, reducing the amount that reaches the eye. Lenses tinted with colour, such as amber or brown , can block out potentially dangerous blue light. Most importantly, sunglasses – or good sunglasses, at least – block out UV rays. But if your glasses don’t have 100% UV protection, then they’ll cause damage, as your pupils will dilate to accommodate the darker view the tint is giving, but won’t then protect you from the increased UV rays that will flood into your wide open eyes.

This film is part of our new series that will provide the blueprint for a scientifically perfect summer. From sweating to hay fever, insects to jet lag, Kate Mulcahy will help you hack summer to engineer the perfect season. Taking a different topic each Thursday, the videos will gradually build up an equation for summer perfection; a summer survival guide certified by science. Subscribe to keep up each week:

Alexander, A. D. and Makas, A. S. (1969) Sunglass lenses and colour fidelity. The Australian Journal of Optometry. 52: 364-369
Glazer-Hockstein C, Dunaief JL (January 2006). "Could blue light-blocking lenses decrease the risk of age-related macular degeneration?". Retina (Philadelphia, Pa.) 26 (1): 1–4.
Langley, R.C. (1971) Gold coatings for temperature control in space exploration. Gold bulletin 4(4): 62-66
Turro, N. J. et al. (2009) Principles of Molecular Photochemistry: An Introduction. p. 29-33
Zigman, S. (1993) Ocular Light Damage. Photochemistry and Photobiology. 57(1): 1060-1068


Hepcats by Kevin MacLeod ( under Creative Commons: By Attribution 3.0 by Moonlight by Kevin MacLeod ( under Creative Commons: By Attribution 3.0

Caribou by daryl_mitchell ( under Creative Commons: Attribution-ShareAlike 2.0 snow goggles by Julian Idrobo ( under Creative Commons: Attribution-ShareAlike 2.0 


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