Whether you are looking for a basic system without a lot of bells and whistles or an ultramodern system that integrates the lights with other pieces of major capital equipment (such as video cameras and monitors), there are five features that are of concern to all buyers: brightness, color, shadow control, heat reduction and maneuverability. Here's a review.

Brightness: a matter of lux
The ideal brightness of the OR lights depends on the procedures you do and the preferences of the surgeons. You will hear lighting systems referred to as being a certain number of lux or footcandles (10.8 lux equals one footcandle). This is all you need to know: the higher the lux, the brighter the light.

There is a strong demand for very bright, wide-diameter lights in open surgeries. A wide-diameter lighthead grabs and retains more light in the surgical field. The quality of the light's reflector system will also have a major impact on its ability to consistently illuminate the surgical field. Other key factors that determine brightness quality are the maintenance of a broad depth of field (lighting that covers a wide area) and consistent illumination with the lights positioned both closer to the patient and at a distance.

Surgeon preference is also a very important factor. Some surgeons simply feel more at home in an OR with very intense lighting. "Some surgeons want the lights to be extremely - sometimes even excessively - bright, because that's what they are used to and what they trained under," says Yasamin Badkoubei of Burton Medical Products.

As a rule of thumb, the more invasive the procedure, the more brightness you'll need. For example, some plastic surgeries, dermatological surgery and endoscopy need less intense lighting than general surgeries.

If all you do is minor surgery in an OR or procedure room, you don't need the high intensity lights and can do just fine with the minor surgery or procedure light lines that most manufacturers offer.

Color: It's got to be true
Surgeons need to be able to see physical structures in their true color. There are two measurements of color you will hear about: color temperature and the Color Rendering Index. Here's the difference.

Color temperature is measured in degrees Kelvin. Higher-color temperatures are desirable in surgery. Think of it this way, say the experts. Look at an object while you are outside in the daytime. Sunlight has a color temperature of 5,000 degrees Kelvin and renders objects in their true color. Then go inside and look at the same object. The color appears different because the color temperature is much lower. If color temperature is too low, objects take on red or pink hues. If it's too high (above about 5,500 degrees Kelvin), objects appear blue.

The Color Rendering Index (CRI) is an industry measurement of how accurately the light reflects an object in its true color relative to the available color temperature. In other words, it's a measure of the color distortion created by man-made lights. A perfect CRI score is 100. Lighting experts say that of the two, color temperature is the more important measurement.

Shadow control
It's important to have lights that maintain what are called contour shadows. You don't want the light to "bleach out" the subtle differences in tissue and vasculature while the surgeon is operating in the surgical field. Your surgeon probably won't notice slight differences in the ways that different lighting systems render the contour shadows in the operative field, but pronounced differences can affect the procedure.

Contrast shadows are obstructions of light caused by the surgical instruments in the operative field or by the surgical team's shoulders, heads, hands or arms moving in front of the lights. Companies have devised different methods for overcoming contrast shadows. One is higher-intensity illumination and the other is altering the size of the lighthead so that the light has a path to go around to compensate for the obstruction. The manufacturers use these methods individually or in combination to achieve shadow control.

Heat reduction
Surgical lights produce a good deal of heat. There's no getting around this fact. However, manufacturers have found ways to dissipate heat and reduce the dreaded "sauna effect" in the OR.

There are two "tricks" to cooling off the heat in the OR. One is that that the modern generation of lights is brighter, but the bulbs need not be of ultra-high wattage. For example, one system, the Berchtold Chromophare, uses halogen gas rather than the traditional tungsten filament. This generates a lot less heat that needs to be dispersed.

Secondly, lighting systems now have increasingly sophisticated internal and external mechanisms of dispersing heat. Some systems use cold-mirror reflectors to keep the heat from hitting the OR team and surgical field. Some are designed to push the heat to the back of the lighthead, away from the heads of the surgical team and the operating field. Once the heat leaves the lighthead, the airflow systems in most ORs help disperse the heat.

Some manufacturers caution that there can be a maintenance trade-off with vented lights. A light can collect dust and cleaning fluids. If you are not vigilant about upkeep, this can affect light output over the life span of the light. To correct this issue, there has been a movement by some manufacturers to using sealed-off lightheads.

Maneuverability
Here are some examples of notable controllability features of the current generation of lights:

• Positioning and focusability. A good lighthead should be lightweight, and the handle easy to operate, so the lights are simple to maneuver and tilt as needed. They should be easy to focus and dim. The suspended overhead lights should drift as little as possible, so that the procedure does not have to be interrupted while the lights are re-positioned. At the high-tech end of the spectrum, systems such as the Harmony System from Steris have touch-button controls for the pattern size, power intensity and focus of the lights.
• Continuous operation. Most systems come equipped with a backup bulb mechanism that kicks on in a fraction of a second if a light burns out during a procedure. When bulbs need to be changed, the process should be simple, so as not to bring the OR to a standstill.
• Integration with other equipment. In some ultramodern ORs, the surgical lights interface with cameras, flat-panel monitors, video cameras and the surgical tables. These systems can be operated from a single control panel or via voice commands (the Hermes system).

Even if you go the more traditional route, you will need to know about how the lighted systems are mounted - on the ceiling or on a track - and how they can function in conjunction with the other pieces of equipment in the operating room, such as monitors on booms.

Try before you buy
The only way to tell if the lights that sound so good on paper are what your surgeons want to be working under is to see them in action. In some cases, manufacturers will help you set up a light trial to assess the system before you buy it. And if that is not possible, they should be able to put you in touch with other end users in the same specialty - both administrators and their surgeons. As in any business, word of mouth and the reputation of the company are powerful predictors of whether you'll become a satisfied customer. Remember, if all goes well, you won't be buying lights again for a long time.