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Glare Index (Cat. 0–4)
The Glare Index indicates the amount of visible light blocked by a pair of sunglasses. The classification ranges from 0 to 4 and defines the level of darkness and suitability for different light conditions.
What is Glare Index?
The Glare Index is a standardised classification that indicates how much visible light is absorbed by a tinted lens. It does not relate to UV protection, but solely to the perceived level of tint.
The categories (0–4)
- Cat. 0 (0–20 per cent) — Very light-coloured lenses, suitable for indoor use or low-light conditions.
- Cat. 1 (20–57 per cent) — Lightly tinted lenses, for moderate light.
- Cat. 2 (57–82 per cent) — Medium lenses, suitable for normal lighting conditions.
- Cat. 3 (82–92 per cent) — Dark lenses, ideal for bright light (everyday outdoor use).
- Cat. 4 (92–97 per cent) — Very dark lenses, for extremely bright conditions (mountains, glaciers). Not suitable for driving.
Why it is important
- Visual comfort — Adequate light absorption reduces glare and eye strain.
- Choosing sunglasses — This allows you to select the category best suited to your needs.
- A luminous experience — It determines how natural outdoor vision is.
- Consistency with one’s lifestyle — Each category meets different needs.
Where is it used?
At Isolani Optical Centres, Glare Index is taken into account when selecting sunglasses to ensure comfort, visual quality and suitability for real-world lighting conditions.
- Sunglasses — Available in all sizes 0–4.
- Polarised lenses — Improved contrast and comfort outdoors.
- Photochromic lenses — They adjust their light absorption.
- Materials — Transparency and composition affect absorption.
Isolani Experience
Each pair of sunglasses is designed with the frame, technical specifications and lifestyle in mind, to ensure the perfect balance between protection, comfort and visual quality.
Ongoing support
The ideal Glare Index depends on your daily use and lighting conditions. At Isolani Optical Centres, we offer ongoing support with adjustments, non-medical checks and updates to your optical solutions whenever necessary.
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The information on this page is provided for information purposes only and relates to the optical and commercial sectors. It does not contain any medical, clinical or diagnostic content.