Page 82 - Lasers and IPLs in Medical/Aesthetic Applications v1.2
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Chapter 1 – Fundamentals of Medical/Aesthetic Lasers and IPLs v1.2
 There are devices available which can ‘measure’ the skin colour. However, good ones are expensive while cheap ones are useless!!
● It is important to properly consider the skin colour when treating a patient/client with light.
● Skin Types 4 and 5 will absorb a lot of visible light due to the high melanin content.
● Type 6 is particularly difficult/impossible to treat with lasers and IPLs. This is because it has a very high content of melanin throughout the full thickness of the epidermis.
Melanin Absorption and Pain
Visible light is absorbed by melanin in the basal layer, particularly towards the blue end of the spectrum. This generates a temperature build-up in that layer, which then conducts heat energy in the epidermis above and the dermis below. Many temperature and pain nerve endings are near the epidermal/dermal junction and so are stimulated by this heat energy. This is the cause of much of the pain felt during photothermal treatments.
We covered this topic in one of our blog posts...
Scattering in the Skin
● As discussed before, light can be imagined as a beam of light particles called photons. A photograph is a ‘graph’ or a recording of photons taken at an instant. Let’s ‘sit’ on a photon of light and see what happens when it enters the skin (animation).
● The first thing you will notice is that as you approach the skin surface you will see quite a lot of photons coming back at you.
● These are the reflected photons which have either been ‘bounced’ from the surface (Fresnel reflections – see section on this) or have emerged from within the skin (see ‘Back-scattering’ section).
● As you enter the skin surface you will ‘see’ the skin as an obstacle course full of objects which you may collide with. However, when you hit one of these objects you don’t necessarily stop – more often than not you will merely change the direction in which you are traveling, a bit like snooker balls striking each other.
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Chapter 1 LEVEL A Fundamentals of Lasers/IPLs
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