Use of right lighting levels essential

According to European Medical Directives, a medical device is a product intended to be used “On humans for: diagnosis, surveillance, examination, treatment and compensation of lost functions.”

Devices are classified in three groups based on the potential risk they pose to patients during use. Low risk products are in Class I, medium risk in Class IIA, medium/high risk in Class IIB and high risk (implants) in Class III.

Medical lights fall into Class I, which means that they are not used directly on the body, do not have to be sterile and are not used for monitoring. Medical luminaires must still, however, comply with several regulations before they can be used. These include EN 60601-1 (General requirements for safety), EN 60601-1-2 (Electromagnetic compatibility – Requirements and tests), EN 60601-2-41 (Particular requirements for the safety of surgical luminaires and luminaires for diagnosis), EN 60601-2-22 (Surgical, therapeutic and diagnostic laser equipment), EN 606010-1-8 (Alarm systems) and EN 60601-2-50 (Photo therapy).

A simple guide to determining which standards a medical light must adhere to can be seen in Figure 1.

Lux requirements

Level of illumination (LUX) is the standard way to measure the lighting capability of a luminaire and the European Directive EN 12464 gives guidelines on light levels throughout the medical environment.

Examination rooms

The examination room is often the entry point to a hospital for a patient and visual inspections by staff play a crucial role in determining the correct treatment. This demands a high level of general lighting and high colour rendering for showing the true colour of the skin. Colour rendering is the ability to bring out an object’s true colours and is measured on the Colour Rendering Index (Ra). The scale used to determine Ra is made from eight primary colour samples and six secondary. The ability of a product to reproduce colours is expressed with the average Ra value. Maximum Ra is 100 and the minimum Ra level for medical equipment is 85.

As patients will not stay in an examination room for long periods, ceiling mounted lights are the best way to obtain a 500 Lux average, according to Norwaybased Luxo. Required Ra in examination rooms is 90.

Luxo recommends that an arm based examination lamp, mounted on a trolley or wall, is an ideal supplement to ceiling lights. Arm based lamps offer strong colour rendering and a focused beam.

Requirements Em/lux Ra
General lighting 500 90
Examination and treatment 1,000 90

Surgery and outpatient facilities

Minor and major surgery demands specialised illumination. The required high levels of illumination with high colour index are achieved by using direct lights. These units need to be sealed to be easy to clean.

Operating lights are normally ceiling mounted and need to be flexible, easy to control and direct light to where it is needed. The illuminated field needs a distinct cut-off to avoid illuminating unwanted areas while maintaining high intensity, excellent colour rendering and shadow reduction. Colour rendering is vital in operating theatres as oxygen rich arterial blood is brighter in colour than venous blood. Needless to say, it is of paramount importance that surgeons can tell the difference between the two in the operating theatre.

The surgeon needs a very high colour rendering to distinguish between different types of tissue. An overlapping multireflector light design provides excellent shadow reduction, even if part of the light is blocked by obstructions. If a bulb burns out, the remaining lamps will work as a backup, ensuring that the procedure is completed without interruptions.

Requirements Em/lux Ra
Pre-op and recovery rooms 500 90
Operating theatre 1,000 90
Operating cavity 40,000–160,000 90

Intensive care units

Patients under prescribed drugs may find it extremely difficult to adjust to high luminance, so Luxo recommends that uplighters are used in intensive care units. These lights prevent direct glare for the patient and avoid reflections that can make screens and monitoring equipment difficult to read. Work carried out in intensive care requires higher colour rendering than a regular ward. This limits the number of light sources to incandescent/halogen bulbs and certain T-5 and TC-L tubes.

Simple examinations of patients can be performed with a downlight positioned in the ceiling above the bed. For more thorough examinations, a separate armbased examination lamp is needed. Unlike reading lamps, examination lights use tungsten halogen lamps for maximum colour rendering and intensity. The light can be wall mounted, fixed to the ceiling or a floorstand for maximum flexibility.

Requirements Em/lux Ra
General lighting 100/400 90
Simple examinations 300/400 90
Examination and treatment 1,000 90
Night watch 20 90

Patient rooms and wards

In general, uplighters are the right choice for wards and downlighters should be used in corridors to prevent the patient from looking directly into luminaires. Hospitals, according to Luxo’s product group manager Martin Holmberg, often request that ward lighting be integrated.

However, for ease of access, lights need to be fitted 1.4 m from the floor and uplighters should be fitted at 2 m to avoid glare.

For reading and examination lights, an arm based luminaire fixed to the wall or furniture is the best choice. Unlike a reading light in a trunking system, an arm based luminaire can be placed wherever light is needed. In wards with multiple beds, the actions of one patient can effect others. By using an arm based luminaire as a reading light, it is possible to create a “private” lit zone which provides illumination for an individual but does not disturb other patients. An arm based luminaire will also provide staff with a supplementary light when attending to the patient.

Modern arm based bedhead luminaires use highly efficient compact fluorescent lamps with good colour rendering and long lamp life. High frequency ballasts provide the user with flicker-free lighting while extending lamp life by reducing power consumption.

Requirements Em/lux Ra
General lighting 100 80
Reading lighting 300 80
Simple examinations 300 80
Examination and treatment 1,000 90
Night/observation lighting 5 80
Bathrooms and toilets 200 80

Corridors

The prime objective of corridor lighting is to illuminate transport areas, and care should be taken to ensure that patients being moved avoid direct glare from luminaires. This can be achieved by installing luminaires that “wash” the wall with light, such as ceiling mounted direct light luminaires with asymmetric light distribution.

Correct lighting can also work as a sign, highlighting doors and giving an indication of direction and depth. This is particularly important for people with impaired vision who use contrast to navigate. Any lights in corridors should also be dimmable for night-time.

Requirements Em/lux Ra
Corridors (day) 200 80
Corridors (night) 50 80

Reception

Lighting in hospital receptions and waiting rooms plays a major role in creating a relaxing and soothing atmosphere for both patients and visitors. The lighting scheme can provide a different atmosphere to various parts of the space, such as bright communal areas to more secluded areas.

Lighting effects can be manipulated according to the varying individual needs, daylight availability or occupancy.

Requirements Em/lux Ra
Waiting rooms 200 80
Day rooms 200 80

Offices

Activities within a typical doctor’s office combine tasks routinely done in a regular office and those conducted in an examination room. Indirect lighting combined with task lighting will provide an optimum working environment for all paper and on-screen work. A decorative, pendant luminaire will help create a friendlier and a less clinical look. For examinations, a wall-mounted arm-based examination luminaire will create the correct level of illuminance and colour rendering for correct diagnosis.

Requirements Em/lux Ra
General lighting 300 80
Examination of the outer eye 1,000 90
Reading and 500 90
colour vision tests
Ear examination 1,000 90

 Information for this article was supplied by Luxo ASA, Norway.