Knowing Your Lens

Written by: editor Jul,18 2013 10:40 AM

Little do people know that their eyeglass' lens goes a long way more in correcting their sight. This issue, Opthalmologist Dr Hoh shares with us about the various tints and coating that makes a world of difference to your eyewear choice. 

Tinted lenses for glasses have always been thought as a fashion accessory.  What is less known is that lens tinting and coating can enhance the vision performance and improve the quality of visual experience.  After you have chosen your spectacle frames, your next decision will be your choice of tint and coating for your lenses.
 




 

Tinted lenses for glasses have always been thought as a fashion accessory.  What is less known is that lens tinting and coating can enhance the vision performance and improve the quality of visual experience.  After you have chosen your spectacle frames, your next decision will be your choice of tint and coating for your lenses.

Colour Tints
Grey or grey-green tint
This is the most common tint colour as it is meant to be colour neutral which means it does not interfere or distort the true colour seen.  In addition, it also enhances vision giving it a more crisp contrast.
 
Amber-brown tint
This also a popular choice as lenses with this colour tint block out blue wavelengths (including ultraviolet light) and are useful for people who enjoy outdoor activities such as golfers or bikers.
 
Yellow tint
This tint also blocks out blue wavelengths and therefore helps to increase visual contrast during overcast sky with lots of clouds or during sunset.  This colour is popular with car or bus drivers and those who play outdoor recreation sports such as tennis or soccer.  It is also the colour of choice for shooters or hunters who shoot with guns.
 
Fashion tints
Fashionable colour tints such as pink, blue or purple do not provide much visual improvement but nonetheless can enhance the wearer’s appearance.  They do not have any detrimental effect and can be used to colour coordinate and match the wearers chosen spectacle frames.
Irrespective of the colour of the tints chosen, the darker the tint, the more light will be blocked out.  Sunglasses will have a very dark tint and is therefore not suitable to be used for driving at night. (Refer Table 1)

Light Transmission Factor (LTF%)
 

Description

Usage

Restrictions

Filter category

100-81%

Very light tint

Cosmetic or indoor use

None

0

80-44%

Light tint

Low sunlight

Careful during night driving

1

43-19%

Medium tint

Medium sunlight

Not for night driving

2

18-9%

Dark tint

Bright sunlight

Not for night driving

3

8-3%

Very dark tint

Very bright sunlight

Not for any driving at all

4
Table 1: Filter category of lenses based on light transmission characteristics 

Mirrored lens coating
This reflects a lot of light and is ideal for those whose job is mostly outdoors in bright sunlight.  These include pilots, police or armed forces, sailors, mountain trekkers, fishermen or skiers where the amount of light transmitted to the eyes is tremendous.  Note that mirrored coating is not available for prescription lenses.
 
Anti-reflective coating 
Anti-reflective coating is used on virtually all lenses as we live in a tropical country with all year round sunshine.  The coating reflects a substantial amount of light and therefore cuts down the glare, making it more comfortable for wearer in bright environment.
 
Hard coating
This coating is meant to protect plastic lenses as they are prone to scratches.  Although they are scratch resistant, they are not scratch-proof and the wearer should still use the spectacles with care!
 
Polychromatic lens
Polychromatic lens become darker when exposed to light and they come in a variety of colours to choose from.  They are convenient as the wearer does not need to get a pair of sunglasses when going from a dark area to a bright place and vice versa. The speed of transition is usually less than 30 seconds.

Polarising lens
Polarising lens cut out half the light from the eyes and is therefore useful in very bright conditions.  There are recommended for people who are by the water areas (sea or lake) or snow-capped areas such as fisherman or skiers or mountaineers.  In these areas, the light entering the eyes is almost double normal as there is reflection from the water or the snow in addition to the sunlight.
In summary, there is a large choice of tints and coating available for the lenses after making a purchasing the spectacles.  Whether for fashion, work or sports, do discuss your visual needs with your optician or optometrist.  There is a definitely a lens that can customized for your needs which will bring out the best of your vision.

Eye Guide

 


 

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