Cone of light

Not to be confused with the Light cone.

The cone of light, or light reflex, is a visible phenomenon which occurs upon examination of the tympanic membrane with an otoscope.^[1] Shining light on the tympanic membrane causes a cone-shaped reflection of light to appear in the anterior inferior quadrant. This corresponds to the 4 o'clock to 5 o'clock position in the right eardrum and the 7 o'clock to 8 o'clock position in the left eardrum.^[2] The apex of the cone is at the most depressed part of the tympanic membrane, known as the umbo.^[3]

Absence of a cone of light

The absence of a cone of light does not necessarily signify an ear disorder, as it could be due to the slope of the tympanic membrane or the shape of the ear canal.^[4] However, distortions in the cone of light can also be a sign of increased middle ear pressure or otitis media.

References

1. Stanley Gelfand (19 March 2009). Essentials of Audiology. Thieme. p. 40. ISBN 978-1-60406-155-0.
2. Cone of Light Anatomy - "..:: The Tympanic Membrane ::". Archived from the original on 2012-04-05. Retrieved 2011-12-24.
3. Advanced Therapy in Otitis Media. PMPH-USA. 2004. p. 56. ISBN 978-1-55009-201-1.
4. Robert Thayer Sataloff; Joseph Sataloff (24 April 2006). Occupational Hearing Loss, Third Edition. CRC Press. p. 38. ISBN 978-1-4200-1547-8.