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When it comes to protecting your eyes from harmful sunlight exposure, understanding sunglasses categories and UV protection is key. This guide will help you navigate the various types of sunglasses and their features, ensuring you make an informed choice for your specific needs.

Sunglasses Categories

Sunglasses are classified into different categories based on their level of UV protection and visible light transmission (VLT). Let's explore these sunglasses categories in detail:

Category 0 Cat 0 lenses are either clear or have a very light tint; they are used for safety glasses or spectacles where you need to see clearly what you are doing. They're also useful for keeping mud out of your eyes when mountain biking on wet trails. These lenses don't really offer any UV protection for outdoor use in bright conditions.

Category 1 Cat 1 lenses are for casual use, used as a comfort filter in cosmetic and fashion eyewear. They provide a low level of sun glare reduction and UV protection. Suitable For: Fashion

Category 2 Cat 2 sunglasses are the most common category to be found in sunglasses. For general use, they provide good protection from visible light and UV rays. This lens will have a medium tint which allows through less light than category 1 but more light than category 3. Suitable For: General Purpose, Watching and Taking Part in Sport

Category 3 Category 3 sunglasses, also known as cat 3 sunglasses, provide extra protection from both visible and UV light. These lenses will usually only allow less than 20% of visible light to penetrate the lens. This means that they will block out 80%+ of light. The sunglasses UV rating category 3 makes them ideal for various outdoor activities. Suitable For: Open Mountain Ranges, Beach Activities

Category 4 Cat 4 lenses provide a high level of protection from visible and UV light. These lenses have a very dark tint and are not to be worn as driving sunglasses, as they are too dark for safe operation of vehicles. These lenses will allow less than 10% of light to transmit through the lens. They are to be used for specific situations only - not for a pair of everyday sunglasses. Suitable For: High altitude trekking and mountaineering

Clearly, there is not a single lens to suit every set of conditions; this is where sunglasses with a range of lenses come in, or photochromic lenses that adapt to the light conditions. Read more here.

Ultraviolet Light (UV) Protection

Overexposure to ultraviolet light is thought to be a cause of cataracts, retinal damage, and other eye problems, so UV protection is an essential function of sunglasses. All our sunglasses offer 100% UV protection; no UV light will pass through the lens. This level of protection is often referred to as UV400, which blocks all light rays with wavelengths up to 400 nanometres, including both UVA and UVB rays.

When choosing sunglasses, look for high UV protection sunglasses that offer UV400 or 100% UV protection.

Visible Light Transmission (VLT)

This is the measure of how much light your sunglass lens lets through to your eye and can be expressed as a percentage. Therefore, a VLT of 1% means very dark glasses indeed, and a VLT of 100% means all the light is getting through and the lens is, therefore, a 'clear lens'.

Rather than quote a percentage for each lens, they are categorised as follows:

• Category 0; 80-100% VLT
• Category 1; 46-79% VLT
• Category 2; 18-45% VLT
• Category 3; 8-17% VLT
• Category 4; 3-8% VLT

Lens Categories and Tints

The most common lens tint is brown; this is because these tinted lenses (along with grey and green) are 'colour neutral', that is, they cut down on overall brightness without distorting colours, thereby accentuating relief. The lens tint can vary from a light tint in Category 1 to a dark tint in Category 3 sunglasses, and a very dark tint in Category 4 sunglasses.

When selecting sunglasses, consider factors such as:

1. The level of UV protection (aim for UV400 or 100% UV protection)
2. The appropriate category for your needs (e.g., category 3 sunglasses for general outdoor use)
3. Lens tint and colour for your specific activities
4. Additional features like polarised lenses for reducing glare

Remember, while style is important, the primary function of sunglasses is to protect your eyes from harmful sunlight exposure. By choosing the right category of sunglasses with proper UV protection, you're taking an important step in maintaining your long-term eye health.

• Choosing Sunglasses - The Key Points
• Polarised Lenses
• Knowledge Base