A review of the principles, uses, methods and techniques of this diagnostic tool.

Dermoscopy (or dermatoscopy) — also known as epiluminescence microscopy or episcopy — is a non-invasive diagnostic tool that helps in the evaluation of the colors and microstructures of the epidermis, dermo-epidermal junction, and papillary dermis, which are not normally visible to the naked eye.

Functionally a dermoscope is similar to a magnifying lens but with the added advantages of having inbuilt illumination, the ability to record images, and a higher magnification that makes it possible to assess structures as deep as in the reticular dermis.

Principle

The basic principle of dermoscopy is transillumination of a lesion and studying it with a higher magnification.1 The principle on which it works is that the light incident on dry, scaly skin is reflected, but smooth, oily skin allows light to pass through it, reaching the deeper dermis; thus by employing application of linkage fluids over the lesions to be studied, subsurface skin structures can be visualized.

Linkage fluids used include oils — immersion oil, olive oil and mineral oil, water, an antiseptic solution and glycerin.

Linkage fluids not used include immersion oil containing chlorinated paraffin, and dibutyl phthalate — which have teratogenic, fetotoxic and carcinogenic effects2,3 — and water or antiseptic solutions, which evaporate quickly.

Basic Design of A Dermoscope

The essential components of a dermoscope include: an achromatic lens, an inbuilt illuminating system and a power supply. Additional facilities in some dermoscopes are an inbuilt photography system — either an attachable conventional or digital camera or an inbuilt camera — and supporting software for the capture, storage, retrieval and even interpretation of images.

Types of Dermoscopy Instruments

Marghoob et al have exhaustively reviewed various models of dermoscopes.4 For simplicity, dermoscopic instruments can be grouped as follows:

1. Instruments without image capturing facility, eg, dermatoscope;
2. Instruments with image capturing facility, eg, Dermaphot; and
3. Instruments with image-capturing facility and analytical capability, eg, DermoGenius Molemap.

Techniques

Dermoscopy can be done by either the non-contact or the contact technique. In the contact technique, the glass plate of the instrument comes in contact with the surface of the linkage fluid applied to the lesion. In the non-contact technique, there is no contact of the lens with the skin; the cross-polarized illumination allows only light in a single plane to pass through it. The non-contact technique has the advantage of not being the source of nosocomial infections;3,5 however, it has the disadvantages of decreased illumination and poor resolution.4

Dermoscope Uses

Dermoscopes have the advantages of higher magnification and visualization of skin structures. They can be helpful in the diagnosis of diseases with typical dermoscopic patterns; invasive skin biopsies can be avoided and images can be captured for records. Table 1 lists the dermoscopic features of some skin diseases.

Limitations: Expense, Need for Training

Dermoscopes are as yet not commonly used in developing countries because they are expensive and are not readily available. Their potential for study of inflammatory and pigmentary dermatoses is waiting to be tapped.

In a survey17 conducted online it was found that 35% of dermatologists believed that dermoscopy required training under an expert, which at present is limited to large dermatology centers. There is also a need to make the learning of dermoscopy easier and to establish a universal method of teaching.

The International Dermoscopy Society and the virtual Consensus Net Meeting18 on Dermoscopy have called for a standardized reporting system and the terminology for reporting.

Dr. Al Aboud is with the Dermatology Department, King Faisal Hospital, Makkah, Saudi Arabia.

Dr. Jain is with the Dermatology Department, Balaji Action Medical Institute, New Delhi, India.

Dr. Ramesh is with the Dermatology Department, Safdarjang Hospital and VM Medical College, New Delhi, India.

Disclosures: The authors disclose that they have no conflict of interest with any subject matter included in this article.