Trichoscopy is the examination of the scalp and hair with a dermoscope, a magnifying instrument that images the surface under controlled lighting. It allows the structures of the scalp and the individual hair shafts to be counted and measured in a fixed area without removing tissue.
The method records the properties that define density. It counts the number of hairs per square centimetre, separates terminal hairs from the finer vellus hairs, and measures shaft diameter. Because miniaturisation, documented in Note 01, is a gradual change in count and calibre rather than a sudden loss, these are the measurements that track it. Repeating trichoscopy on the same marked area over time produces a quantified record of change.
Two features make it suited to a controlled study. It is non-invasive, so the same area can be imaged repeatedly across the length of a study, and it is quantitative, producing counts and measurements rather than impressions. It also allows a treated area to be compared against a vehicle-treated control under the same imaging conditions.
The OF·27 program used trichoscopy as its measurement in a twelve-week study conducted against a vehicle control. The design and results of that study are documented in the next note.