What is Dermoscopy?
Dermoscopy is the examination of skin using microscopy. It is also known as dermatoscopy (mainly in the US), and epiluminoscopy (in some french speaking countries).
How does a Dermatoscope work?
A dermatoscope is a hand held device which combines the following three key elements:
Magnifying optics
Usually 10x
Illumination
Most modern dermatoscopes have LED lighting.
Removal of surface scatter
Removal of surface light reflection, or scatter, enables visualisation of deeper structures.
More on removing surface light reflection/scatter..
The final part, being able to remove surface light and scatter is what enables the device to go beyond simple magnification. Imagine looking through glass, or into a pond. Your vision is obscured by random scatter and reflection of incident light. This can be removed by introducing a fluid interface, for example a glass bottomed boat will remove the air between the ocean and your eye, enabling a much clearer view.
The same effect is achieved in a dermatoscope by polarising the light entering or leaving the dermatoscope.
From the two photos here, the one on the left is taken with a polarised filter, which allows much better visualisation of what is happening beneath the water compared to the picture on the right, where a polarised filter was not used.
Doing this with a dermatoscope can allow visualisation down to the stratum corneum. See the example below of the same mole visualised with one, two and three of the key elements.
Magnification
Surface reflection does not allow a clear view of the mole, and the detail is limited as a result
+ Polarisation
Detail becomes more visible with added polarised light, and you can start to see some of the pigment network
+ Fluid Interface
Using alcohol gel as a fluid interface allows the clearest visualisation of the pigment network
"I've seen lots of Dermatologists not using a fluid interface...why is that?"
Indeed, it may now be confusing to learn that there are polarised and non-polarised dermatoscopes! Many modern dermatoscopes are however capable of both so you should be able to swap between the two fairly easily. Non-contact dermoscopy: - Requires your dermatoscope to have a polarised light function - No need for a fluid interface - Allows for rapid review of multiple skin lesions - Advantage in non-pigmented lesions as it can be used without applying any pressure to the skin (therefore doesn't blanch any vascular structures) Contact dermoscopy: - Required if your dermatoscope does not have a polarised light function - Need a fluid interface e.g. alcohol gel - Need to apply the dermatoscope directly onto the skin - More advantageous in pigmented lesions
Using a Dermatoscope
When conducting a dermatological examination, you should always start with macroscopic evaluation. Before you look with the dermatoscope, you should have an idea of what your suspected diagnosis is, and then use the dermatoscope to look for the features which would support or go against that diagnosis.
You then need to examine with the dermatoscope, either in polarised non-contact mode, or in contact mode with fluid such as alcohol gel or aqueous gel. Your eye should be very close to the dermatoscope. Once you've visualised the lesion, then focus the lens until clear.
As you can see from the image, you will need to get very close to the patient! Don't let that put you off, just explain what you will be doing and don't forget to breathe!