Are cheap sunglasses bad for your eyes?

Question

Conventional wisdom and tips in magazines often state that you shouldn't buy cheap sunglasses because they don't protect well against UV rays.

There are two claims in one here, I am skeptical about:

1. Do cheap sunglasses (with UV protection notice on them) really offer significantly worse protection? I am skeptical because UV coating or just some materials that do not pass UV light through aren't necessarily expensive.

2. How harmful is the UV light that reaches the eyes? It is always suggested that the answer is 'very harmful', but that does not need to be the case. Reasons to be skeptical: people don't wear clear glasses with UV protection in the winter, so the significance here is the difference of amount of UV light being received with sunglasses on and off (due to wider open irises). Another point is, how long do you need to wear sunglasses on in the sun, for this difference to have real measurable impact on your eyes.

Answer 1

In Australia, there is a mandatory standard for the labelling of sunglasses to help the consumer.

In 2003, the Australian Competition and Consumer Commission (ACCC), a consumer watchdog issued a Regulation Impact Statement about the standard. Here is an historical copy.

In the document, they discuss the risks of poor-quality sunglasses.

Some are irrelevant to your question:

• "Coloured sunglasses can reduce the ability to see traffic light signals"
• "Sunglasses that are too dark are unsafe for driving"
• "Sunglasses should not be made of flammable materials"
• "Sunglasses should be robust enough to minimise the risk of eye injury"

Some are related:

Solar ultraviolet light causes cataracts

Long term exposure to solar ultra violet radiation is a risk factor for cataracts, a very common eye disorder that results in loss of vision. The prevalence of significant cataracts is 25 per cent in people aged 65-74 and over 40 per cent in those aged more than 75 years.

Cataract surgery imposes a very significant annual cost on the community. Over 120 000 cataract operations are performed in Australia each year. Australia’s cataract surgery rate is 6 300 per million, which is higher than the USA and the UK. About 0.3 per cent of the population suffers from blindness due to cataracts.

[...]

Visible light poses little hazard to the eyes at the levels commonly encountered, although long term exposure to short wavelength (blue) light has been implicated in the development of age related macular degeneration. Sunglasses are principally used to reduce glare, which is caused by high levels of visible light or by light in inappropriate places.

Infra-red radiation has wavelengths longer than visible light, and poses little hazard to the eye, as the amount reaching the eye under normal conditions is low. Protection against infra-red radiation is mainly required by people working in industries in which they receive a high exposure, such as people working with molten metals.

Ultraviolet radiation has wavelengths shorter than visible light. Exposure to high levels of environmental ultraviolet radiation is common in Australia. In addition to the well known association between ultraviolet exposure and melanoma, chronic exposure to ultraviolet radiation has been implicated in serious eye disorders including cataract, pterygium and age related macular degeneration. Acute exposure to intense ultraviolet radiation can produce photokeratoconjunctivitis (sometimes known as snow blindness).

It also talks about "Hazards associated with dimension and strength of frames" - i.e. that if the lenses are too small, the protection will be insufficient no matter what the filtering it performs.

Finally, it also discusses price, and shows expensive sunglasses may be poor, and cheap sunglasses may be fine.

Price is not an assurance of safety

Consumers cannot rely on price as an indicator of quality. Past enforcement experience shows that some very high priced sunglasses do not necessarily conform to the Australian Standard.

...

Price is not really an indication of compliance and it has been found that many cheaper priced sunglasses do comply with the standard.

Answer 2

1. This Health Canada page says, "For most people, an inexpensive pair of sunglasses will do the job" and "Look for a label that lists the type and amount of protection" (with details on how much protection to expect).

2. It also says, "Sensitivity to ultraviolet radiation varies from one person to the next", and "Some scientists believe that routine exposure to blue light over many years may age the retina and increase the risk of blindness in some people over the age of sixty", and more.

Answer 3

Regarding question 2, I think there is no clear evidence that sunglasses will reduce eye problems.

Of course, direct sun exposition (eg. solar eclipses, mountain sports, etc.) without protection can cause retina and cornea damage (1), for those cases protection is recommended, but I mean long term exposition.

Many problems have been associated to UV light: pterygium, cataracts, AMD and some more. (2, 3)

But there are still totally different positions like:

The studies on the link between UV exposure and cataract have been many and varied. The acute induction of lens opacities was demonstrated many years ago by Pitts and his colleagues2.5~b-9u9t the dose required was very much greater than that for photokeratoconjunctivitis and much greater than that incurred from a day in the sun. The role of UV in the chronic development of cataract took longer to demonstrate but is now universally accepted. (2)

On the other hand:

Despite the large body of laboratory evidence that ultraviolet radiation (uvr) is cataractogenic, epidemiological studies of the relationship between age-related cataract and chronic uvr exposure have provided apparently conflicting results. An explanation for these conflicting results could be related to errors in dosimetry. Failure to account for the biophysical, physiological and behavioral factors, as well as ground reflectance, which determine the level of uvr exposure of the lens can lead to completely wrong assignments of lifetime exposure. It is argued that by overlooking these factors, past epidemiological studies of uvr and cataract could readily be expected to produce conflicting results. (4)

And:

Although most health scientists now agree that health risks to the skin (e.g., skin cancer) exist from exposure to the ultraviolet radiation in sunlight, a scientific consensus has not really been achieved vis-à-vis sunlight and ocular health. A growing number of scientists warn of hazards to the eye if ultraviolet radiation — and perhaps even shorter wavelength visible radiation also — is not filtered by lenses. Despite a substantial literature on the adverse effects of ultraviolet radiation (UVR) and intense light upon ocular structures, particularly upon the retina, controversy still surrounds the question of whether the levels of natural and man-made light sources are damaging when encountered under normal viewing conditions. Although scientific evidence accumulates to indicate that chronic exposure conditions may accelerate ageing processes in ocular tissues, the quantitative question of “How much is safe?” remains to be answered conclusively. (5)

As for question 1, I presume that genuine sunglasess in the EEA with the CE marking are pretty safe. Possibly even cheap plastic sunglasess won't be harmful under normal conditions (at least I haven't found any research that supports the "pupil dilation" argument).

The supposition that, because of pupil dilation, there are greater influxes of solar UV and short-wavelength visibile radiation when some sunglasses are worn is wrong. It is based on an incomplete and, therefore, misleading analysis. That analysis is particularly defective in ignoring the attenuation of the more highly actinic shorter wavelengths. This paper provides the most nearly complete analysis that is now possible. It treats both the geometric and radiometric aspects of ocular irradiation. A survey of over 400 retail sunglass lenses of all types showed that all would reduce UV radiation densities in all parts of the crystalline lens and on the retina. With spectral actinic weighting, the effective reductions would be even greater. (6)

1. Solar retinopathy after the 1999 solar eclipse in East Sussex
2. Dain, S. J. (2003), Sunglasses and sunglass standards. Clinical and Experimental Optometry, 86: 77–90
3. The Family of Sunlight-Related Eye Diseases
4. Epidemiological studies of sunlight and cataract: the critical factor of ultraviolet exposure geometry
5. Photoprotection of the eye – UV radiation and sunglasses
6. Sunglasses, pupil dilation, and solar ultraviolet irradiation of the human lens and retina