The beauty of the optical touch screen is that it can handle input from passive objects (like a plastic pointer or even gloved hands) and it supports multitouch input. So, if you're working in the operating room and you need a multitouch touch screen, then you're probably looking at an optical touch screen device.
I've been testing the Lenovo ThinkCentre M90z that has an optical touch screen. The touch screen is very easy to use, it's responsive (does not require any pressure), and I can use it even if I'm wearing surgical gloves. I'm not a surgeon, but it's nice to know that this is the type of device that could work nicely in an emergency room or a surgical suite.
How does optical touch work? Here's a brief description from NextWindow:
Working together, two optical sensors track the movement of any object close to the surface by detecting the interruption of an infra-red light source. The light is emitted in a plane across the surface of the screen and can be either active (infra-red LED) or passive (special reflective surfaces).
At the heart of the system is a printed circuit controller board that receives signals from the optical sensors. Its software then compensates for optical distortions and triangulates the position of the touching object with extreme accuracy.
Some of NextWindow's products, such as the 1900 series, use low-profile optical sensors mounted on the surface of the glass. Other products use different configurations. In all models, the infrared light source and optical sensors are synchronized using a sophisticated algorithm that also reduces the effect of ambient light, creating an very clear, accurate screen.