By Elisa Botting
Our increasingly interconnected world has led to an explosion in fashion trends and online shopping. These fashion trends have boosted the market for low-priced sunglasses – the small accessory that can cause great damage to your vision when made of poor quality materials. At first glance, ‘affordable’ and easily disposable sunglasses seem like an attractive option – but are these lenses actually enhancing UV rays and causing long term damage to your eyes?
First popularised in the 1970s, sunglasses protect your eyes from two main types of UV radiation, UVA and UVB. These two wavelengths can cause mutations that lead to skin cancer and other eye diseases including ocular melanoma (a rare type of eye cancer), macular degeneration (an eye disease that results in your vision becoming progressively worse) and cataracts (the formation of dense cloudy areas in the lens of the eye). Sunglasses also protect your eyes from visible light to prevent your eyes from experiencing glare, which can lead to photokeratitis that damages the surface layer of the cornea.
Whilst UV protection standards exist in most countries and the companies producing these sunglasses use a ‘spectral effectiveness’ function in their calculation of solar UVA transmittance, they also often have a longer-wavelength limit for UVA radiation – the main type of radiation responsible for damaging effects induced by UV radiation (Rabbetts& Sliney, 2019). The latter point has brought the level protection given by cheap sunglasses from UV into question. In addition to this, cheap sunglasses often advertise their UV protection by the level of darkness of the lenses. However, the darkness of the lens has little to do with the level of UV protection it offers. Rather, a ‘dip-dyeing process’ is responsible for how much UV radiation is prevented from entering your eyes (Magri et al., 2017. The risk of having cheap sunglasses that have dark lenses but offer no UV protection is that dark lenses cause your pupils to dilate – providing a greater area over which UV radiation can enter your eye and cause long-term adverse health effects, such as ocular melanoma and cataracts (Moran Eye Center, 2018).
In contrast to these long-term effects, short term consequences of cheap sunglasses include the strain that they have on ocular muscles. Uneven tinting of the lenses and warped lenses of different sizes can cause migraines. In addition to this, cheap sunglasses also often fail to protect eyes from visible light by blocking less than the required 75-90% of this type of radiation (Abney & Scalettar, 2021). In order to fully protect eyes from visible light, sunglasses should be constantly absorbing wavelengths of 400 nm (Abney& Scalettar, 2021). If sunglasses fail to do so, your eyes may experience glare that can then develop into photokeratitis – which is short-term damage caused to the surface layer of the cornea that can disappear after 48 hours (Rabbetts& Sliney, 2019). Whilst the condition disappears relatively quickly, it causes redness and swelling that can be extremely painful to an individual.
Despite scientists broadly reaching consensus on the amount of UVB transmittance sunglasses should have, there are many disagreements on the amount of UVA that sunglasses should allow to pass (Rabbetts& Sliney, 2019). Reasons for this include uncertainties around necessary side-protection requirements to protect the eyes from other types of cataracts, the long wave requirement of UV protection and the extent of long term effects on the cornea and retina from UVA and short wavelength visible region (Rabbetts& Sliney, 2019). Thus, more in-depth research is needed to make an overall judgment on the extent to which cheap poor quality sunglasses damage your eyes.
Abney, J. R. & Scalettar, B. A. (1998) Saving Your Students’ Skin. Undergraduate Experiments that Probe UV Protection by Sunscreens and Sunglasses. Journal of chemical education. [Online] 75 (6), 757–.
How to Tell If Your Sunglasses Are Really Protecting Your Eyes. (2018) Available from: https://healthcare.utah.edu/healthfeed/postings/2018/07/sunglasses.protect.php [Accessed Jun 10, 2021].
Magri, R. et al. (2017) Building a resistance to ignition testing device for sunglasses and analysing data: a continuing study for sunglasses standards. Biomedical engineering online. [Online] 16 (1), 114–114.
Rabbetts, R. & Sliney, D. (2019) Technical Report: Solar Ultraviolet Protection from Sunglasses. Optometry and vision science. [Online] 96 (7), 523–530.