How to read surgical light specifications in a tender datasheet

Central illuminance Ec

Central illuminance, written Ec, is the light level at the centre of the field at 1 m from the light head, measured in lux. Typical premium surgical lights reach 160,000 lx. The SIMEON HighLine Sim.LED 8000 and 5000 list 160,000 lx and a dimming range of 48,000 to 160,000 lx, and the Lojer Q-Flow 700 mm head lists a maximum of 160 klux.

More lux is not automatically better. Surgeons seldom work at maximum, glare tires the eyes, and heat grows with output. Look for a wide dimming range so that the team can lower the light for endoscopic or superficial work, and check irradiance alongside it, see surgical light heat emission.

Light field diameter d10 and d50

The field diameter d10 is the diameter at which illuminance falls to 10 percent of Ec; d50 is the same at 50 percent. A larger d10 gives the surgeon a wide, soft field, and the ratio d50 to d10 describes how sharply the field is defined. The SIMEON 8000 lists d10 of 170 to 320 mm at 1 m, and the 5000 lists 180 to 280 mm.

Adjustable field size is useful: a small field for a precise incision, a wide one for a larger exposure. Ask whether the adjustment is mechanical, by the handle, or fixed by head design.

Depth of illumination

Depth of illumination describes how far above and below the focal plane the light stays usable, which matters in deep cavities. Datasheets usually give it in centimetres, measured by a defined method in the IEC standard. Two lights with the same Ec can differ strongly here, because depth depends on the optics and the number of angles light arrives from.

Request the figure and the measurement conditions, and then test it in the room with a deep cavity model or a bowl. The principle of multi-angle light is described in how shadowless lights work.

Colour temperature, Ra and R9

Colour temperature in kelvin describes whether the light looks warm or cool. Surgical lights are generally neutral to cool, and some offer a choice: the Lojer Q-Flow offers 3,700, 4,400 and 5,100 K, and the SIMEON multicolour heads offer 3,500 to 5,500 K. Ra is the general colour rendering index, and R9 describes saturated red. Q-Flow lists Ra 98 and R9 98; the SIMEON BusinessLine lists Ra 96.

Read the next article for more: colour temperature and CRI. When you tender, ask for R9 as a minimum and for the ability to keep rendering constant while colour temperature changes.

Other items on the datasheet

• LED service life, for example above 60,000 h on the SIMEON HighLine and BusinessLine heads.
• Power consumption of the light head, for example 28 W on the Sim.LED 4500.
• Protection class of the housing, such as IP54 for the Sim.LED 8000.
• Turbulence intensity for laminar airflow rooms, 15.9 percent for the Q-Flow 700 mm heads against a limit of 37.5 percent in DIN 1946.
• Number of heads, backup concept, camera and monitor options, handle type and control method.

How to use the numbers in a tender

Write minimum values for Ec, dimming range, d10, Ra, R9 and colour temperature, and state that the figures must be measured per IEC 60601-2-41 and supported by a test report. Compare offers at a similar configuration: dome count, arm type and options. The Sim.LED 5000, the SIMEON BusinessLine range and the Lojer Q-Flow give a useful range of examples to benchmark against.

Beckfinity can provide the manufacturer datasheets and help you convert them into a specification. Request a quote or a consultation from our specialists for your project.