Nowadays, affordable sunglasses are readily available at various retailers. However, their ubiquity may raise concerns about their protective capabilities. While they often meet basic UV protection requirements, their overall quality, including visual clarity, can be unsatisfactory. With summer approaching, selecting sunglasses that not only complement your style but also provide proper eye protection is crucial.
Opticians, on the other hand, adhere to strict national health regulations, obligating them to meet higher standards such as the CE and UKCA marks. They are equipped to assist customers in finding sunglasses that fulfill their practical requirements, ensuring comfort and compatibility with their facial features.
Rules for Protection
European law classifies sunglass lenses as “personal protective equipment,” outlining five levels of protection. Category 0 lenses allow 80-100 percent of light transmission, while category 4 lenses permit only 3-8 percent, making them unsuitable for driving. Category 3 lenses are the most commonly used, as they are appropriate for various situations, including driving.
Contrary to popular belief, darker lenses do not necessarily offer better protection. The appropriate level of light absorption depends on the intended use and location. Category 4 lenses are designed for extremely bright environments like high mountains or deserts but may impair visibility in other settings. Nevertheless, all sunglasses that meet established standards provide adequate UV protection.
Quality of Vision
Wearing sunglasses may give the impression of hindered vision. Tinted lenses selectively filter light, allowing certain wavelengths while restricting others. Understanding three key concepts can clarify this phenomenon and its significance.
Visual acuity refers to the sharpness of vision, measured by asking individuals to read progressively smaller letters on a chart. An ideal result is approximately 100 percent. However, this test is conducted under specific lighting conditions and does not account for variations in visual quality in different lighting scenarios.
Contrast sensitivity is the ability to distinguish objects from their surroundings. It is more challenging to discern black letters on gray backgrounds compared to white backgrounds.
Lastly, refractive errors can affect both visual acuity and contrast sensitivity, leading to conditions like astigmatism and nearsightedness or farsightedness. Wearing non-prescription sunglasses with these conditions can further impair vision.
Colour Matters
Lens color is another important consideration. While it does not affect protection, it can influence contrast and the perception of brightness. Each color filters out different wavelengths of light.
Grey lenses filter out all wavelengths equally, resulting in a neutral tint. Brown or green lenses have varying effects on light absorption, leading to brighter perception through brown lenses, darker perception through grey lenses, and more natural perception through green lenses.
Plastic or Glass Lenses?
Lens material also plays a role in visual quality. Most sunglasses utilize specialized plastics known as organic lenses, but glass lenses, also known as mineral lenses, are available as well.
Organic lenses are lighter and more durable, while mineral lenses are more scratch-resistant and less prone to color distortion. Consequently, mineral lenses provide superior visual clarity.
Polarised Lenses
Polarised lenses block light that reaches the eye at a certain angle after reflecting off surfaces like roads or water, reducing glare. They are ideal for driving or spending time near water.
However, polarised lenses may not be suitable in all situations. They can obstruct light from screens, making them appear darker or even completely black, requiring users to adjust their devices for better visibility. Additionally, they may not be optimal for certain winter sports, as they can eliminate glare, making it difficult to detect icy patches on the ground.
Other Features
Certain design features also warrant consideration when choosing sunglasses.
Gradient lenses are darker at the top, gradually fading to a lighter tint at the bottom. They typically absorb around 85 percent of light in their darkest area and 10 percent in the lightest. While stylish, their UV protection remains consistent throughout the lens.
Reflective lenses have a coating on their outer surface that reflects light, enhancing protection. However, this coating can be easily scratched or damaged.
Lenses with anti-reflective coating on the inside of the lens improve visual clarity by eliminating light reflected from behind the wearer. This treatment is often applied to large sunglasses or glasses with high-quality lenses.
In the event of any uncertainty, consulting with an optician or optometrist is strongly advised to find the sunglasses that best meet your individual needs.
