INTRODUZIONE ALLA TRICOLOGIA

TRICHOLOGICAL MICROSCOPY IN POLARIZED LIGHT

hair and polarized light

dr. Andrea Marliani
dermatologo - endocrinologo
in Firenze

Microscopy in polarized light, traditionally used in mineralogy, is now also of indisputable value in trichology.
Keratin, a sequential, repeating crystalline protein, has the property of retarding the wave of polarized light passing through it, so that under the microscope a hair appears as luminous and coloured against a black ground.
Retardations of the wave due to the thickness of the keratin are defined as "polarization colours" and each colour corresponds to a precise diameter. Those also resulting from the crystallographic pattern and from pigments are defined as "compensation colours".
Just as in mineralogy the colours denote membership of a precise crystalline order, in trichology they permit appraisals of the hair's structure, that is, its keratinous "quality", thus supplying data for otherwise only hypothetical evaluations.
- Since "compensation colours" can only be assessed on the basis of their sequence during rotation, the slide must be studied on a rotating plane and never with a light transmitted by an optical fibre.
- An ocular micrometer is indispensable for matching the colours to be seen with the true diameter of the hair under examination. Knowing the true thickness and seeing the polarization colours makes it possible at the clinic to match the observed keratinous fibre under examination.

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