Class 3B vs. Class IV Lasers

Summary

• Some Class III laser manufacturers have issued comparative claims; these should be evaluated independently.
• All medical lasers are regulated by the FDA based on use and risk classification.
• Class IV lasers are classified by their power output and intended use.
• Claims about dosage or penetration depth should be supported by appropriate evidence.
• Wavelength (in nanometers) influences how far light may travel in tissue.
• Power (in watts) affects how quickly energy is delivered.
• Class IV lasers may produce a warm sensation due to power and wavelength settings.
• Heating is typically superficial and limited to outer skin layers.
• Laser-tissue interaction depends on factors like wavelength and tissue properties.
• Unabsorbed photons may pass through non-targeted tissue and dissipate.
• Proper dosage settings are essential for safe and effective use.

Misconceptions About Class IV Lasers and Online Claims

Some manufacturers of Class III laser devices have made public claims suggesting that Class IV therapy lasers may present safety concerns. These claims often appear without reference to specific FDA warnings or formal notices.

It’s important to note that both Class III and Class IV therapy lasers are regulated by the FDA and must meet applicable safety and performance standards before being legally marketed.

Class IV therapy lasers are FDA-cleared medical devices and, like all medical devices, should be operated by trained professionals in accordance with manufacturer guidelines and safety protocols.

Differences in laser classifications—such as power output, wavelength, and treatment beam characteristics—can affect how the device is used in clinical settings. These parameters should be considered when evaluating the appropriate technology for a given professional application.

All Lasers Require FDA 510(k) Clearance

All laser devices—whether for medical or non-medical applications—are regulated by the FDA through the Center for Devices and Radiological Health (CDRH), with a focus on safety, including eye safety.

Devices that have received 510(k) clearance are issued an official letter from the FDA. This letter outlines the cleared indications for use and specifies whether the device is designated for use by licensed medical professionals (Rx only) or for over-the-counter (OTC) consumer use.

FDA Oversight of Class IV Therapy Lasers

The first Class III therapy laser received FDA 510(k) clearance in 2001, and the first Class IV therapy laser received clearance in 2003. All medical lasers, including Class IV devices, are subject to FDA regulation through the Center for Devices and Radiological Health (CDRH). To date, there is no public record of the FDA issuing a permanent recall or banning the sale of any Class IV therapy laser based solely on allegations of thermal injury or safety concerns.

FDA Warning Letters Issued to Laser Manufacturers

The Food and Drug Administration (FDA) requires that all medical device manufacturers, including those producing Class III and Class IV lasers, comply with current Good Manufacturing Practices (cGMP) as outlined in the Quality System Regulation (21 CFR Part 820). Manufacturers are subject to routine inspections to assess compliance with these requirements.

If an inspection identifies deficiencies, the FDA may issue a Warning Letter describing the observations and specifying a timeline for corrective action. These letters are publicly available online.

• Since 2001, multiple manufacturers of Class III laser devices have received FDA Warning Letters. In some instances, companies have discontinued operations following regulatory actions.
• Since 2003, one manufacturer of a Class IV laser device is publicly listed as having received an FDA Warning Letter and later voluntarily ceased operations in 2011.

All Medical Devices Involve Risk and Require Proper Use

All medical devices carry some level of risk if not used appropriately, including Class III and Class IV lasers. Devices such as ultrasound and diathermy, which rely on thermal mechanisms of action, have been associated with deep tissue burns when not used correctly. Despite this, they have remained in clinical use for over 50 years.

A common precaution with thermal-based devices is to avoid use over metal implants due to the risk of tissue heating. In contrast, some Class IV lasers operate via a photochemical mechanism rather than a thermal one. When used according to their FDA-cleared indications and by trained professionals, certain models may be used in areas near metal implants.

Some Class III laser manufacturers have labeled Class IV lasers as “surgical only.” However, Class IV is a broad FDA classification that includes various technologies—such as CO₂ and YAG lasers—some of which are surgical, while others are cleared for non-surgical applications.

FDA Reporting System for Adverse Events Involving Lasers

The FDA maintains a public database known as MAUDE (Manufacturer and User Facility Device Experience), which collects reports of adverse events involving medical devices. This includes any reported incidents of harm or injury potentially associated with the use of laser systems.

There are a greater number of entries involving Class III therapy lasers and LED pads than Class IV therapy lasers in the MAUDE database. One possible explanation is that certain lower-power devices may be used without operator supervision, which may increase the potential for user error.

Most reports associated with Class IV lasers involve surgical or aesthetic procedures—such as hair removal, tattoo removal, or tissue ablation—which are distinct in purpose and application from non-surgical therapy uses.

Note: Over the past 14 years, in my experience working with both human and veterinary cases, I have not personally encountered a serious burn or tissue injury resulting from the proper use of Class IV therapy lasers. As always, the safe use of any medical device depends on adherence to established protocols and professional oversight.

Class IV Laser Overdose Claims Are Not Supported by Regulatory Evidence

Some sources reference the “Arndt-Schulz Law” in an effort to justify the use of lower power and dosage parameters, asserting that higher-powered devices, such as Class IV therapy lasers, may exceed an alleged "therapeutic window," potentially resulting in excessive exposure to energy.

It is important to note that the “Arndt-Schulz Law” originated in pharmacology and has been referenced in various alternative health models over time. While some concepts related to dose-response relationships are relevant in energy-based modalities, the Arndt-Schulz principle is not a regulatory standard, nor is it universally accepted as a scientifically established law within medical device usage.

The Reality of Class III Lasers – Under-Dosing Remains a Common Concern

Much of the research aimed at identifying optimal dosage parameters for photobiomodulation has been conducted in vitro. These controlled studies allow for precise measurements and have, in some cases, observed an apparent range of energy exposure within which cellular response is most active, with diminishing response noted beyond that range.

However, caution should be exercised when attempting to directly apply in vitro findings to complex biological tissues. Variability in tissue type, depth, and patient-specific factors can all influence how energy is absorbed and utilized, and current literature continues to explore these dynamics. The interpretation of “optimal dose” in clinical applications remains an evolving subject.

Some researchers and clinicians have raised concerns regarding the energy output of certain Class III therapy lasers, suggesting that these systems may deliver lower dosage levels than what some practitioners aim to apply in clinical settings. Manufacturers of these devices often cite a large body of studies—reportedly over 3,000—supporting Low-Level Laser Therapy (LLLT). However, summaries of some of these studies indicate that outcomes were not always statistically different from placebo groups, which may be attributed in part to low dosing parameters.

In the book Laser Therapy: Clinical Practice and Scientific Background, Dr. Jan Tunér and Lars Hode review numerous studies involving low-power laser devices. Here are some key observations from their analysis:

• In many of these studies, analysis uncovered one or more reasons for the negative findings reported, the most common being the use of extremely low doses.
• The trend in laser therapy for the past 10 years has been to increase power density and dose.
• There is no point in increasing the dose if the wavelength has a low penetration factor; the penetration of the particular wavelength must be taken into account.
• We must rely on clinical observations in some areas, though scientific support may be limited.

They further suggest that higher-powered devices may offer broader therapeutic potential, though such opinions are based on anecdotal experience and not intended as definitive claims of efficacy.

It should also be noted that some Class IV therapy lasers may deliver energy levels that fall below the parameters typically associated with higher energy applications, which could limit their effect in certain use cases. This observation does not imply a lack of benefit, but rather reflects variability in intended use and treatment protocols.

Key Consideration:
Appropriate energy dosage—based on wavelength, power output, treatment duration, and individual patient variables—is an important parameter in designing laser-based treatment protocols. Clinicians should always follow the device’s cleared indications for use and consult manufacturer guidelines when determining dosage parameters.

Class III therapy Lasers Are Often Not Considered Effective by Insurers

While the FDA has cleared the device for marketing, some payers have not recognized Low-Level Laser Therapy (LLLT) as a reimbursable service. Published data on LLLT have shown variability in outcomes, making it challenging to determine consistent clinical benefit. Additionally, with an estimated nine to twelve sessions often cited, the overall cost—ranging from approximately $1,000 to $1,500—may be considered high, particularly in light of limited consensus in the medical literature regarding therapeutic value.

Source: Position Paper on Low Level Laser Therapy (LLLT) 12 pages

Aetna considers cold laser therapy investigational due to a lack of sufficient evidence in the published medical literature demonstrating its effectiveness for wound healing, pain management, or other uses such as musculoskeletal conditions, arthritis, or neurological disorders.

Source: Aetna: Clinical Policy Bulletins, Number 0363, Subject: Cold Laser Therapy

Some manufacturers of Class III therapy lasers reference "super pulsing" capabilities, suggesting that brief, high-peak power pulses allow for deeper light penetration compared to Class IV therapy lasers. These claims often cite extremely short pulse durations—on the scale of nanoseconds—but do not consistently reference validated testing methods or equipment capable of measuring actual tissue penetration depth.

Although peak power outputs of 25,000 mW to 50,000 mW may be advertised, these figures do not reflect the average power output, which is a more relevant factor in determining the total energy delivered over time. Average power is derived from peak power, pulse duration, and pulse frequency. For example, a 50,000 mW peak power device with brief pulse durations may yield an average output of approximately 0.050 mW. At that output, delivering 1 joule of energy would require extended treatment durations.

Class IV therapy lasers, which typically operate at higher continuous wave power levels (e.g., 10 watts), deliver energy at a faster rate. For example, at 10 watts CW, 6,000 joules may be delivered over a 10-minute period. Claims regarding efficacy or comparative performance between laser classes should be interpreted cautiously and supported by peer-reviewed, clinically validated evidence.

Claims Favoring Class III Super Pulsing Over Class IV Lack Sufficient Scientific Support

Some manufacturers of Class III therapy lasers reference "super pulsing" capabilities, suggesting that brief, high-peak power pulses allow for deeper light penetration compared to Class IV therapy lasers. These claims often cite extremely short pulse durations—on the scale of nanoseconds—but do not consistently reference validated testing methods or equipment capable of measuring actual tissue penetration depth.

Although peak power outputs of 25,000 mW to 50,000 mW may be advertised, these figures do not reflect the average power output, which is a more relevant factor in determining the total energy delivered over time. Average power is derived from peak power, pulse duration, and pulse frequency. For example, a 50,000 mW peak power device with brief pulse durations may yield an average output of approximately 0.050 mW. At that output, delivering 1 joule of energy would require extended treatment durations.

Class IV therapy lasers, which typically operate at higher continuous wave power levels (e.g., 10 watts), deliver energy at a faster rate. For example, at 10 watts CW, 6,000 joules may be delivered over a 10-minute period. Claims regarding efficacy or comparative performance between laser classes should be interpreted cautiously and supported by peer-reviewed, clinically validated evidence.

Claim That Class III Special Frequencies Are Effective – Not Supported by FDA Clearance

Many Class III therapy lasers incorporate protocols that reference the use of special frequencies. These frequencies are sometimes described as being applicable to muscles, joints, organs, and other anatomical regions.

However, many of the frequencies referenced in these protocols appear to be derived from other modalities—such as electrical stimulation—rather than from laser-specific clinical studies. For example, Nogier’s frequencies, originally associated with auricular therapy using electrical stimulation in humans, have been adapted into some laser protocols for both human and veterinary contexts.

Two important considerations arise: First, there is a lack of published clinical data validating the clinical use of these specific frequencies in laser applications. Second, these frequency-based applications have not received FDA 510(k) clearance for the therapeutic indications in which they are sometimes promoted.

Class IV Therapy Lasers Represent A New Generation Of Laser Technology

The principles of laser physics demonstrate that longer wavelengths may allow for deeper penetration into tissue. Deeper penetration is often considered important for reaching musculoskeletal, vascular, lymphatic, and neurological structures. If Class III lasers are considered less effective in certain contexts, it may be due to factors such as lower energy delivery or limited penetration. Class IV lasers offer higher power levels, specific wavelengths, larger treatment beam sizes, and operating modes that are designed for deeper tissue exposure when used appropriately by trained professionals.

Summary of Characteristics for Class IV Therapy Lasers

Class IV lasers are distinguished by six notable features:

Greater Energy Delivery

Capable of delivering significantly more energy—up to 1,500 times more than Class III lasers—potentially supporting shorter application times.

Deeper Light Penetration Depth

Typical Class III lasers have reported light penetration ranges of approximately 0.5–2.0 cm². Class IV lasers are capable of delivering light to deeper tissue levels, with some systems reporting penetration depths up to 10 cm², depending on parameters such as wavelength, power, and tissue characteristics.

Expanded Treatment Coverage

Class III systems often deliver energy over areas ranging from 0.3–5.0 cm², varying by model and manufacturer. Class IV systems may support treatment coverage up to 77 cm², which may be considered when addressing larger anatomical regions.

Larger Treatment Surface Area

Class III devices may cover a treatment area of approximately 0.3–5.0 cm², depending on the model and manufacturer. Class IV devices may cover areas up to approximately 77 cm². A larger surface area may allow for broader application in certain clinical settings.

Greater Power Density

Power density refers to the concentration of energy delivered per unit area. This measurement is one of several parameters considered in the use of photonic devices.

Continuous Wave Power

In many Class III lasers, the power is pulsed or modulated for a portion of the total operating time—often around 50 percent. This means light may be emitted from the probe intermittently during use. In contrast, many Class IV lasers are designed to operate in Continuous Wave (CW) mode, which can deliver a consistent level of output over a defined time period, depending on the settings and application.

Laser Beam Transmission

Some evaluations suggest that a portion of the light energy produced by certain Class III lasers may not reach the end of the probe due to transmission losses. Class IV lasers often utilize fiber optic cables designed to support efficient delivery of laser energy from the source to the treatment probe.