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A surgical light – also referred to as an operating light or surgical lightheadis a

medical device A medical device is any device intended to be used for medical purposes. Significant potential for hazards are inherent when using a device for medical purposes and thus medical devices must be proved safe and effective with reasonable assura ...

intended to assist medical personnel during a

surgical procedure Surgery ''cheirourgikē'' (composed of χείρ, "hand", and ἔργον, "work"), via la, chirurgiae, meaning "hand work". is a medical specialty that uses operative manual and instrumental techniques on a person to investigate or treat a pat ...

by illuminating a local area or cavity of the

patient A patient is any recipient of health care services that are performed by healthcare professionals. The patient is most often ill or injured and in need of treatment by a physician, nurse, optometrist, dentist, veterinarian, or other health c ...

. A combination of several surgical lights is often referred to as a “surgical light system”.

History

Technical development

In the mid-1850s, operating rooms were built towards the southeast with windows in the ceiling to benefit from natural sunlight as much as possible. The biggest problem was the dependence of lighting and whether a surgical procedure could be done on the time of day and weather conditions. Furthermore, a doctor, nurse or medical equipment easily blocked the light. The use of mirrors on the four corners of the ceiling to reflect sunlight towards the operating table only slightly alleviated these problems. Attempts were made to use an optical condenser in an indirect light to reduce the

heating A central heating system provides warmth to a number of spaces within a building from one main source of heat. It is a component of heating, ventilation, and air conditioning (short: HVAC) systems, which can both cool and warm interior spaces. ...

, but without success. The entrance of

electric light An electric light, lamp, or light bulb is an electrical component that produces light. It is the most common form of artificial lighting. Lamps usually have a base made of ceramic, metal, glass, or plastic, which secures the lamp in the soc ...

s into the operating room in the 1880s was accompanied by problems. With early electrical technology control of the light emitted was poor. Electric light was still moving and diffuse, with great

heat radiation Thermal radiation is electromagnetic radiation generated by the thermal motion of particles in matter. Thermal radiation is generated when heat from the movement of charges in the material (electrons and protons in common forms of matter) is ...

Light-emitting diodes A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (cor ...

as light sources remove the problem of heat radiation and reduce energy requirements.

Terminology and measurements

; Lux : Unit for the amount of visible light measured by a luxmeter at a certain point. ; Central illuminance (Ec) :

Illuminance In photometry, illuminance is the total luminous flux incident on a surface, per unit area. It is a measure of how much the incident light illuminates the surface, wavelength-weighted by the luminosity function to correlate with human brightness ...

(measured in lux) at 1m distance from the light emitting surface in the

light field The light field is a vector function that describes the amount of light flowing in every direction through every point in space. The space of all possible '' light rays'' is given by the five-dimensional plenoptic function, and the magnitude of ea ...

centre. ; Light field centre : Point in the light field (lighted area) where illuminance reaches maximum lux intensity. It is the reference point for most measurements. ; Depth of illumination : The distance between the points of 20% illumination intensity above and below the center point. From the point of maximum illumination, which is the center of the light field 1 meter from the light-emitting surface, the photometer is moved toward the light until the light intensity measured falls to 20% of the maximum value. The distance between the center and this point is defined as L1. The similarly measured distance in the direction away from the light is L2. The depth of illumination without needing to refocus is the sum of the two distances L1 and L2. In the second edition of the IEC standard, published in 2009, the threshold value was revised from 20% to 60%. ;

Shadow A shadow is a dark area where light from a light source is blocked by an opaque object. It occupies all of the three-dimensional volume behind an object with light in front of it. The cross section of a shadow is a two-dimensional silhouette, o ...

dilution : The light's ability to minimize the effect of obstructions. ; Light field diameter (D10) : Diameter of light field around the light field centre, ending where the illuminance reaches 10% of Ec. The value reported is the average of four different cross sections through the light field centre. ; D50 : Diameter of light field around the light field centre, ending where the illuminance reaches 50% of Ec. The value reported is the average of four different cross sections through the light field centre

Norms and requirements for surgical light

The

International Electrotechnical Commission The International Electrotechnical Commission (IEC; in French: ''Commission électrotechnique internationale'') is an international standards organization that prepares and publishes international standards for all electrical, electronic and r ...

(IEC) created the document ''IEC 60601-2-41 – Particular requirements for the basic safety and essential performance of surgical luminaires and luminaires for diagnosis, 2009 '' to establish norms and guidelines for the characteristics of a surgical and examination light to secure safety for the patient as well as lower the risk to a reasonable level when the light is used according to the user manual. Some of the standards for surgical lightheads are the following: *Homogeneous light: The light should offer good illumination on a flat, narrow or deep surface in a cavity, despite obstacles such as

surgeon In modern medicine, a surgeon is a medical professional who performs surgery. Although there are different traditions in different times and places, a modern surgeon usually is also a licensed physician or received the same medical training as ...

s' heads or hands. *Lux: The central illuminance should be between 160,000 and 40,000 lux. *Light field diameter: The D50 diameter should be at least 50% of D10. * Colour rendition: For the purpose of distinguishing true tissue colour in a cavity, the colour rendering index (Ra) should be between 85 and 100. *

Backup In information technology, a backup, or data backup is a copy of computer data taken and stored elsewhere so that it may be used to restore the original after a data loss event. The verb form, referring to the process of doing so, is "back up", w ...

possibility: In case of interruption of the

power supply A power supply is an electrical device that supplies electric power to an electrical load. The main purpose of a power supply is to convert electric current from a source to the correct voltage, current, and frequency to power the load. As a r ...

, the light should be restored within 5 seconds with at least 50% of the previous lux intensity, but not less than 40,000 lux. Within 40 seconds the light should be completely restored to the original brightness. *Announcement: The IEC document also mentions what needs to be notified to the user. For example, the

voltage Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to m ...

and

power consumption Electric energy consumption is the form of energy consumption that uses electrical energy. Electric energy consumption is the actual energy demand made on existing electricity supply for transportation, residential, industrial, commercial, and o ...

should be marked on or near the lampholder as well as on the lighthead. In the instructions for use the following should be announced. ** Cleaning and

decontamination Decontamination (sometimes abbreviated as decon, dcon, or decontam) is the process of removing contaminants on an object or area, including chemicals, micro-organisms or radioactive substances. This may be achieved by chemical reaction, disinfecti ...

of the surgical light ** Safety aspects of the

optical filter An optical filter is a device that selectively transmits light of different wavelengths, usually implemented as a glass plane or plastic device in the optical path, which are either dyed in the bulk or have interference coatings. The optical p ...

(purpose and warning to prevent removal) ** Central illuminance ** Light field diameter ** Depth of illumination ** Shadow dilution ** Correlated colour temperature and colour rendering index ** Total

irradiance In radiometry, irradiance is the radiant flux ''received'' by a ''surface'' per unit area. The SI unit of irradiance is the watt per square metre (W⋅m−2). The CGS unit erg per square centimetre per second (erg⋅cm−2⋅s−1) is often used ...

** Cleaning and

disinfecting A disinfectant is a chemical substance or compound used to inactivate or destroy microorganisms on inert surfaces. Disinfection does not necessarily kill all microorganisms, especially resistant bacterial spores; it is less effective than st ...

** Handling of the lighthead in case of failure ** How the user should respect the national rules for hygiene and disinfecting

References

* Extrait de la revue Techniques Hospitalières noo 400 Janvier/1979 "L’éclairage en salle d’opération" by M. Hainault p. 47 * IEC International, 60601-2-41 Medical electrical equipment - Part 2-41: Particular requirements for the basic safety and essential performance of surgical luminaires and luminaires for diagnosis {{Refend Medical equipment Types of lamp Light fixtures