Wavelength, power and dose: reading a Class IV laser specification

What "Class IV" means

Laser classes describe the hazard a laser presents, not how well it treats. Class IV (Class 4 under IEC 60825-1) covers lasers with a continuous output above 0.5 W. At that power the beam can harm the eye and skin, so Class IV therapy lasers are used with protective eyewear for everyone in the room, controlled access and trained operators.

Wavelength

Wavelength, measured in nanometres (nm), decides how light interacts with tissue. Different wavelengths are absorbed to different degrees by water, haemoglobin and melanin. Red light (around 650 nm) is absorbed close to the surface; near-infrared wavelengths such as 810, 915 and 980 nm are less strongly absorbed by melanin and haemoglobin and reach deeper tissue. Many therapy lasers combine several wavelengths. When comparing systems, check which wavelengths are included and whether each can be controlled independently or only in fixed combinations.

Power and energy

Power is measured in watts (W). One watt delivers one joule (J) of energy per second, so energy = power × time. A laser running at 10 W for 60 seconds delivers 600 J. Higher power delivers a given amount of energy in less time; it does not by itself mean a better treatment.

Dose is usually expressed as energy (J) or energy density (J/cm²), which is energy divided by the treated area. Ask how a system's protocols calculate and display dose, and whether you can see the energy delivered in each session.

Continuous and pulsed output

In continuous-wave (CW) mode the output stays at a constant power. Pulsed and superpulsed modes deliver short bursts of higher peak power separated by pauses. For pulsed output, the figure that determines energy delivered over time is the average power, not the peak. When a specification lists a high peak power, also look for the average or CW power and the pulse frequency range.

What to compare on a specification sheet

• Wavelengths, and whether each is independently controlled
• Continuous (CW) power, average power and peak power, each stated separately
• Pulse modes and frequency range
• Handpieces and lenses, including contact and off-contact options
• Safety features: eyewear supplied, interlocks, emergency stop
• Software: built-in and custom protocols, dose display, patient records
• Battery or mains operation, weight and portability
• Medical Device Authority (MDA) registration in Malaysia
• Local installation, training, warranty and service support

Next step

Specification sheets are easier to judge side by side and in use. TRIMAX supplies Summus Medical Laser Class IV systems and can arrange a demonstration at your clinic.

This article is general technical information. A qualified clinician should decide whether laser therapy is suitable for each patient and follow the manufacturer's instructions for use.