VLT stands for Visible Light Transmission. Put simply, it is the percentage of light that the lenses allow through to your eyes.

A sunglasses lens with a VLT of 20% allows 20% of light to pass through filtering out the other 80%.

You should always consider the VLT when you are choosing the best sunglasses for your activity.

• The best sunglasses for bright conditions will typically have a VLT of 10-15% and blue, green, or gray lens colors.
• Sunglasses that can be worn in both full sunlight and shady conditions like on a deck or verandah have a VLT of between 15-25% and have a variety of different lens colors.
• And sunglasses that are for specialist activities, like fly fishing in low light conditions should have a VLT of between 25 and 40% and usually have either yellow or copper color lenses.