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Visual acuity during direct laryngoscopy at different illuminance levels.

Paul A Baker¹, Amy S Raos, John M D Thompson

¹Department of Paediatric Anaesthesia, Starship Children's Health, Auckland, 1142, New Zealand. p.baker@auckland.ac.nz

Anesthesia and Analgesia

|January 11, 2013

Summary

Optimal laryngoscope illumination for anesthesiologists is around 700 lux, improving visual acuity without further gains at 2000 lux. Subjective preference, however, favored higher light levels for clarity during direct laryngoscopy.

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Area of Science:

Anesthesiology
Medical Devices
Ophthalmology

Background:

Adequate illumination is critical for effective direct laryngoscopy, a procedure essential for airway management.
The International Organization for Standardization (ISO) 7376:2009 standard sets minimum illuminance requirements for laryngoscopes.
Objective data correlating laryngoscope light intensity with visual acuity during the procedure were previously lacking.

Purpose of the Study:

To objectively assess the relationship between varying levels of laryngoscope illuminance and anesthesiologists' visual acuity during direct laryngoscopy.
To compare objective visual performance with subjective assessments of light adequacy and clarity at different illuminance settings.

Main Methods:

Fifty anesthesiologists performed direct laryngoscopy on manikins with near vision charts at illuminance levels of 50, 200, 700, and 2000 lux.

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Participants' visual acuity was measured using both near charts at the manikin larynx and standard wall charts at a distance.

Subjective feedback on light brightness, clarity, visual performance, and suitability was collected at each illuminance level.

Main Results:

Visual acuity significantly improved with increasing illuminance up to 700 lux (P<0.0001), with notable deficits at 50 and 200 lux.
No statistically significant improvement in visual acuity was observed when illuminance increased from 700 lux to 2000 lux.
Subjective ratings indicated a preference for 2000 lux for clarity and performance, despite objective visual acuity plateauing at 700 lux.

Conclusions:

Laryngoscope illuminance up to 700 lux is associated with improved visual acuity during direct laryngoscopy.
Increasing illuminance beyond 700 lux does not yield statistically significant improvements in objective visual acuity.
Anesthesiologists' subjective preference leans towards higher illuminance (2000 lux) for optimal clarity and performance during the procedure.