What does UV400 mean on sunglasses?

UV400 means the lenses block all ultraviolet radiation with wavelengths up to 400 nanometres, covering both UVA and UVB rays entirely. It is the gold standard for UV protection and is the minimum you should look for when buying sunglasses. A UV400 rating gives complete UV protection regardless of how dark or light the lens tint is.

What is the difference between polarised and non-polarised sunglasses?

Polarised lenses contain a chemical filter that blocks horizontally-oriented light waves, which are the primary cause of glare reflecting off flat surfaces like water, roads, and car bonnets. Non-polarised lenses reduce overall light levels but do not eliminate glare selectively. Polarised lenses are significantly better for driving, fishing, and water sports.

What is Cat 3 on sunglasses?

Cat 3 refers to Lens Category 3, which reduces visible light transmission by 83–92%. It is the most common category for general outdoor use, beach, and sunny conditions. Cat 3 lenses are safe for driving and provide strong protection in bright sunlight, making them the most widely sold category worldwide.

What is Asian fit in sunglasses?

Asian fit — also called Low Bridge Fit — refers to frames designed for faces with lower nose bridges, higher cheekbones, and wider face profiles, which are common in East Asian and Southeast Asian populations. These frames feature higher or adjustable nose pads and adjusted frame angles to prevent the lenses from sitting too close to the face or resting on the cheeks.

What does VLT mean in sunglasses?

VLT stands for Visible Light Transmission, which is the percentage of visible light that passes through a lens. A low VLT percentage means a darker lens that lets in less light, while a high VLT means a lighter lens. For example, a VLT of 10% is very dark (suitable for bright sun), while 80% is nearly clear (suitable for overcast or low-light conditions).

Sunglasses Glossary

A plain-English reference for every lens and frame term you'll encounter when shopping for sunglasses. Jump to any term using the alphabetical index.

A

Anti-Slip Nose Pads: Rubberised or hydrophilic nose pad inserts that grip the nose more effectively when wet with sweat or rain. They are an important feature for sport and active use, where standard smooth nose pads tend to slide down the face during exercise. Hydrophilic materials become even grippier when wet, making them particularly effective in Singapore's humid conditions. Many performance sunglasses brands include replaceable anti-slip nose pads as standard.
Asian Fit: Also called "Low Bridge Fit," Asian fit refers to frames specifically designed for faces with lower nose bridges, higher cheekbones, and wider face profiles — anatomical features common in East Asian and Southeast Asian populations, including many Singaporeans. Standard Western-cut frames often sit too low on the face or rest on the cheeks due to these differences. Asian fit frames feature higher nose pads, steeper temple angles, and adjusted lens positioning to ensure the lenses sit at the correct height in front of the eyes. Many major brands — including Oakley and Maui Jim — offer Asian fit versions of their popular models.

C

Carbon Fibre Temples: Temple arms (the side pieces that rest on the ears) made from or reinforced with carbon fibre material. Carbon fibre is exceptionally light and extremely rigid, making it a premium feature in high-performance eyewear. Frames with carbon fibre temples offer a barely-there feel on the face during extended wear. They are common in high-end cycling and triathlon sunglasses where weight and vibration resistance matter. Carbon fibre temples are generally found in upper-mid to premium price brackets.
Cat 0 (Lens Category 0): Cat 0 lenses reduce visible light by 0–19%, meaning they are essentially clear or carry only a very light cosmetic tint. They offer little to no meaningful reduction in brightness and are classified as decorative rather than protective eyewear. Cat 0 lenses are not suitable for use in bright sunlight or outdoor conditions. They may be used in very low-light environments or as fashion frames with no functional sun protection. In Singapore's high UV environment, Cat 0 sunglasses provide insufficient protection for daytime outdoor use.
Cat 1 (Lens Category 1): Cat 1 lenses reduce visible light by 20–57%, making them a light-tint option suited to overcast skies, indoor-outdoor transition environments, or low-light conditions. They are not recommended for driving in bright sunlight and are not suitable for Singapore's typical outdoor daytime conditions. Cat 1 is occasionally used in fashion eyewear where a subtle tint is desired. Some photochromic lenses fall into Cat 1 in their lightest state when indoors. Always check the category if you're buying lightly-tinted lenses and plan to use them outdoors.
Cat 2 (Lens Category 2): Cat 2 lenses reduce visible light by 58–82%, offering medium protection suitable for general outdoor use in moderate sunlight conditions. They work well on partly cloudy days or in environments with softer light levels. Cat 2 is a reasonable choice for indoor-outdoor use or transitional lighting, but may feel insufficient in Singapore's intense midday sun. Some lifestyle and fashion sunglasses sit in this category. Cat 2 lenses are generally considered adequate for driving in medium sunlight conditions.
Cat 3 (Lens Category 3): Cat 3 lenses reduce visible light by 83–92% and are the most common outdoor sunglasses category worldwide. They are designed for bright sunshine, beach environments, and general outdoor use — and are rated safe for driving. The vast majority of sunglasses sold globally are Cat 3, and this category is the standard for quality outdoor eyewear. For Singapore's conditions, Cat 3 provides strong protection for most activities, though the UV index here regularly reaches extreme levels. See also: Are Cat 3 sunglasses enough for Singapore?
Cat 4 (Lens Category 4): Cat 4 lenses reduce visible light by 93–97%, making them the darkest available category. They are designed for extreme brightness conditions — high-altitude mountaineering, glacier travel, and intense snow environments where reflected UV is exceptionally high. Cat 4 lenses are NOT safe for driving, as they reduce visibility too severely for safe road use. In Singapore's context, Cat 4 is rarely necessary for everyday use. They may be relevant for specific outdoor activities like open-water sailing in intense midday conditions, but Cat 3 with UV400 protection suffices for most Singaporean outdoor activities.

F

Frame Fit: Frame fit describes how a pair of sunglasses sits on the face, encompassing several key measurements: frame width (total width of the front), lens width (width of each individual lens), bridge width (the gap between lenses that sits over the nose), and temple length (the length of the arms from hinge to tip). A correctly fitted frame should sit level on the face without sliding, with lenses positioned directly in front of the eyes. Poor frame fit leads to discomfort, lens fogging, and reduced eye protection. Many brands provide a measurement guide on the inside arm of their frames.

L

Lens Tint: Lens tint refers to the colour applied to sunglass lenses, which affects how light is filtered and how the wearer perceives contrast and colour. Different tints have different effects: grey tints reduce brightness while preserving natural colour balance; brown and amber tints enhance contrast and are popular for driving and outdoor sports; yellow and rose tints improve contrast in low-light conditions; green tints offer good colour accuracy with moderate contrast enhancement. The tint colour does not indicate the level of UV protection — UV protection is a separate lens treatment independent of colour.

M

Mirrored Lenses: Mirrored lenses have a reflective metallic coating applied to the outer surface of the lens that reflects a portion of incoming light before it enters the lens. This reduces the overall amount of light reaching the eye, which can be beneficial in extremely bright conditions. Mirrored coatings also create a visual privacy effect — others cannot see the wearer's eyes from the front. Mirror coatings are available in various colours (silver, gold, blue, red) and are a cosmetic choice as much as a functional one. The mirror coating does not affect UV protection, which is determined by the base lens material.

P

Photochromic Lenses: Photochromic lenses contain light-sensitive molecules that react to UV radiation by darkening automatically when exposed to sunlight and lightening again when moved indoors or into shade. This makes them highly versatile for activities that move between indoor and outdoor environments. The speed of darkening and lightening varies by brand and temperature — cold conditions typically accelerate darkening while heat can slow it. Most photochromic lenses do not darken inside vehicles, as windscreens block the UV light that triggers the reaction. See also: Photochromic Sunglasses Guide.
Polarised Lenses: Polarised lenses contain a special chemical filter aligned in horizontal rows that selectively blocks horizontally-oriented light waves. When sunlight reflects off flat surfaces — such as water, roads, car bonnets, or wet pavement — it becomes predominantly horizontally polarised, creating intense glare. Polarised lenses eliminate this specific type of glare, dramatically improving visual clarity and comfort. They are particularly effective for driving, fishing, water sports, and any activity near reflective surfaces. Polarisation is a separate feature from UV protection — a lens can be polarised without offering UV400 protection, though quality polarised sunglasses typically include both. See also: Polarised vs Non-Polarised Guide.
Polycarbonate Lenses: Polycarbonate is a high-impact-resistant thermoplastic material widely used in sunglass and safety eyewear lenses. It is significantly lighter than glass while being far more shatter-resistant, making it the standard choice for sport and active use. Polycarbonate lenses inherently block UV radiation as part of their material composition, though a UV400 coating is still often added. They are more prone to scratching than glass or higher-grade optical materials, so anti-scratch coatings are commonly applied. Polycarbonate lenses offer an excellent balance of safety, weight, and cost for active sunglasses.

T

TAC Lenses: TAC stands for Tri-Acetate Cellulose, a layered lens construction commonly used in polarised sunglasses across the mid-range market. A standard TAC lens is built from multiple bonded layers: a TAC base layer, a polarising film, an adhesive layer, and often additional coatings for UV protection and scratch resistance. TAC lenses are lightweight and produce effective polarisation at a lower manufacturing cost than premium injected polarised lenses. They are generally less optically pure than high-end polycarbonate or glass options, but represent good value for everyday and sport use. Many sunglasses in the $30–$150 price range use TAC lens construction.
TR90: TR90 is a thermoplastic polyamide material used extensively in sport and performance sunglass frames. It is notable for its combination of very low weight, significant flexibility, and strong durability — it can bend considerably without breaking and returns to its original shape. These properties make TR90 frames comfortable for extended wear and resistant to damage from drops or impacts. TR90 also maintains its shape well under heat, which is important in Singapore's climate. Most mid-range to premium sport sunglasses use TR90 or similar nylon-based materials for their frames.

U

UV400: UV400 is a protection standard indicating that the lenses block all ultraviolet radiation with wavelengths up to 400 nanometres — covering the full UVA (315–400nm) and UVB (280–315nm) spectrum entirely. It is considered the gold standard for UV eye protection and is the minimum standard you should look for when purchasing sunglasses. Crucially, UV400 protection is a separate property from lens darkness — a very light or clear lens can carry full UV400 protection. In Singapore, where the UV index regularly reaches extreme levels (11+), UV400 should be considered non-negotiable. See also: UV400 Sunglasses Guide.

V

VLT (Visible Light Transmission): VLT stands for Visible Light Transmission and is expressed as a percentage representing how much visible light passes through a lens. A low VLT percentage — such as 8–15% — means a very dark lens that blocks most incoming light, suitable for bright sun. A high VLT — such as 70–90% — means a near-clear lens better suited to low-light or overcast conditions. VLT is directly related to the lens category system: Cat 4 lenses have VLTs of 3–8%, Cat 3 lenses 8–17%, Cat 2 lenses 18–43%, Cat 1 lenses 43–80%, and Cat 0 lenses above 80%. Some goggle and sport sunglass brands publish VLT alongside the category rating to help users select the right lens for specific conditions.