Dermatoscopy or reflected light microscopy offers the possibility of a non-invasive examination of the skin and is particularly useful for the early detection of melanomas and other forms of skin cancer. Dermatoscopy can also be used to assess parasites, foreign bodies,or bleeding.
The dermatoscope normally consists of a focusable magnifying optic, a diode illumination,and a contact disc, which is placed directly on the skin. Depending on the device and manufacturer, the dermatoscope allows for a 10xto 40x magnification.
Let’s discuss the physical basis of dermatoscopy and look at why the skin surface should be wetted with liquid before dermatoscopy is performed.
The superficial keratinocytes are seedless anucleated and the skin surface is irregular. Then we place the dermatoscope with its contact disc on the skin.
Due to the irregular surface of the skin, the light hitting the skin is largely reflected by the stratum corneum and only partially resorbed.
As a result, the light penetrates less deeply into the epidermis and dermis, and we are less able to assess the any skin changes in the depths of the skin.
The more irregular the surface of the skin, the more light rays are reflected and the less light penetrates into the epidermis and dermis. Due to this,deep-lying structures are difficult to assess.
In order to reduce the amount of reflected light, the contact disc is wetted with liquid. This way, there are no air pockets between the contact disc and the skin, thus ensuring the skin surface is smooth:
There are significantly fewer reflections and more light can penetrate into the depth of the skin. Without liquid, structures can only be assessed in the epidermis.
When used with liquid, it is possible to assess structures up to the stratum reticulare of the dermis. In the past, oil or glycerine was used as contact fluid, because these liquids remained on the skin longer.
We offer 90 minutes of intense dermatoscopy compromised knowledge build into 9 online lessons using primary images of Prof. Dr. Kittler from the Medical University of Vienna.