Head mirror versus headlight: illumination, visual identification and visual acuity for otolaryngological examination

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Introduction

The head mirror is the most recognisable symbol of an otorhinolaryngologist. In certain cultures, the head mirror is as common as the stethoscope, if not more so, in artists' renderings and popular depictions of doctors. Introduced in 1743 by the French accoucheur Levert for examining the larynx, today's head mirror has withstood the test of time.¹However, an increasing number of doctors are starting to use battery-powered headlights instead of head mirrors. Some otolaryngologists question whether the head mirror can continue to sustain its relevance and trump its younger technological sibling, the battery-powered or fibre-optic headlight.

During our training years, many of us were told of the multiple advantages of the head mirror, the most important of which was the ability to align one's eye sight and the light source axis, which theoretically facilitated the identification of details within narrow and often tubular spaces during the otorhinolaryngological examination.²However, there is no clear evidence to support this statement.

In this study, we aimed to evaluate and compare the head mirror and various headlights, through the measurement of illumination, visual identification and visual acuity, while using these instruments under conditions simulating a clinical otorhinolaryngological examination.

Materials and methods

Head mirror and headlights

The head mirror used in the study was manufactured by Nagashima (Tokyo, Japan) and had the following specifications: 89 mm diameter and 13 mm round aperture, with a fibre forehead band.

Three types of headlight were tested: the Kimscope 1 W (model: SLL 01 Warm) (Seahanul Biotech, Anyang, South Korea); the Kimscope 3 W (model: SLL 02 Warm; Seahanul Biotech); and the LumiView Portable Binocular Microscope (Welch Allyn, Skaneatelese Falls, New York, USA). All these headlights emitted warm light, similar to the light source when using a head mirror.

Illuminance

Illuminance was measured using a portable lux meter (Sanpometer LX 1010BS; Sanpo Instrument, Shenzhen, China). The mean spectral sensitivity ± standard deviation (SD) of the meter at 600-620 nm (warm light) was approximately 55 ± 5 per cent, as claimed by the manufacturer.

The lux meter was placed and secured on an examination chair headrest. Illuminance was measured and recorded while the head mirror or headlight directly illuminated the meter sensor from a...