Introduction

Wavelength is one of the most important parameters in veterinary laser therapy. Different wavelengths interact with biological tissue differently, affecting absorption, scattering, transmission, and the distribution of light within tissue.

However, wavelength should not be considered a simple indicator of treatment depth. Actual light delivery also depends on tissue composition, pigmentation, coat characteristics, irradiance, treatment time, spot size, and application technique.

Understanding these factors can help veterinary professionals choose a laser system and treatment parameters more appropriately for different patients and clinical objectives.

 

What Is Wavelength in Laser Therapy?

Wavelength describes the distance between corresponding points of a light wave and is measured in nanometers (nm).

When therapeutic laser light reaches tissue, several things can happen:

Reflection → Scattering → Absorption → Transmission

Some photons are reflected from the tissue surface. Others are scattered or absorbed by tissue components, while some continue through the tissue.

The balance between these processes varies with wavelength and tissue characteristics.

This is why two laser systems with similar output power can produce different patterns of light delivery when they use different wavelengths.

 

Why Does Wavelength Matter?

Biological tissues contain different chromophores, including melanin, hemoglobin, water, and cellular components that can interact with light.

The absorption and scattering characteristics of these components vary across different wavelengths.

As a result, wavelength can influence:

•  How much light is absorbed near the surface

• How much light is scattered

•  How much light reaches deeper tissue

•  How photons interact with biological chromophores

•  How treatment parameters should be selected

 

However, wavelength is only one part of the treatment equation.

A practical way to view laser therapy is:

Wavelength + Dose + Irradiance + Treatment Time + Treatment Area + Tissue Characteristics

 For a broader explanation of how these parameters work together, see power, wavelength, and dose in Class IV veterinary laser therapy

Absorption and Scattering

Absorption

Absorption occurs when photons are taken up by molecules within tissue.

Different chromophores absorb different wavelengths to different degrees. Melanin and hemoglobin can influence light transmission, while water becomes increasingly important at longer wavelengths.

The amount of absorption therefore contributes to differences in how various wavelengths behave in tissue.

Scattering

Scattering changes the direction of photons as they travel through tissue.

Scattering is influenced by both tissue structure and wavelength. In general, scattering tends to decrease as wavelength increases within commonly used red and near-infrared therapeutic ranges.

This can affect how light is distributed throughout tissue.

Transmission

Transmission refers to photons continuing through tissue without being absorbed.

The goal of veterinary laser therapy is not simply to maximize transmission. The goal is to deliver an appropriate amount of therapeutic light to the intended treatment area.

 

Why Is 650nm Used in Veterinary Laser Therapy?

Wavelengths around 635–650nm are in the visible red range and are commonly used in photobiomodulation.

Compared with many near-infrared wavelengths, red light is generally more strongly attenuated by superficial tissue. This makes 650nm particularly relevant when the intended treatment area is relatively superficial.

Clinical situations in which superficial light delivery may be relevant include:

• Superficial wound management

• Skin-related treatment

•  Surgical incision support

•  Localized superficial tissue treatment

•  Surface-level photobiomodulation

• 
  

However, 650nm should not be considered a “skin-only” wavelength. The actual treatment response depends on the complete protocol and the characteristics of the target tissue.For a focused discussion of postoperative applications, see veterinary laser therapy after soft tissue surgery.

 

Why Is 810nm Commonly Used?

810nm is one of the most widely studied near-infrared wavelengths in photobiomodulation.

Its tissue interaction characteristics differ from those of visible red wavelengths, making it a commonly used option when treatment involves tissues located beneath the superficial layers.

Depending on the treatment protocol, 810nm may be considered for:

•  Muscle

•  Joints

•  Tendons

•  Ligaments

•  Other soft tissues

• 
  

The wavelength alone, however, does not determine whether a therapeutic dose will reach a particular structure. Irradiance, fluence, treatment time, tissue thickness, and application technique also matter.

 

What About 915nm and 980nm?

915nm and 980nm provide additional near-infrared options for veterinary therapeutic laser systems.

Their optical characteristics differ from shorter wavelengths, including differences in absorption and transmission.

Depending on the device, tissue characteristics, and overall treatment protocol, these wavelengths may be considered when treating:

•  Soft-tissue rehabilitation

•  Musculoskeletal treatment

•  Joint-related conditions

•  Larger treatment areas

•  Deeper anatomical targets

Rather than assigning each wavelength to a specific disease, it is more appropriate to consider the wavelength together with the target tissue and complete treatment protocol.

 

Why Is 1064nm Important?

1064nm is a near-infrared wavelength used in some high-power therapeutic laser systems.

Compared with shorter wavelengths, 1064nm has different scattering and absorption characteristics in biological tissue. These characteristics may support light delivery when the intended treatment area involves larger or relatively deep anatomical regions.

Potential applications include:

•  Deep muscle treatment

•  Joint and periarticular tissues

•  Large-breed dogs

•  Equine rehabilitation

•  Large-animal sports medicine

•  Deeper soft-tissue targets

  These optical characteristics can be particularly relevant in equine rehabilitation, where substantial muscle and connective tissue may lie between the treatment surface and the intended target.

  
  

For more information, see 1064nm Veterinary Laser Therapy for Equine Rehabilitation.

 

650nm vs 810nm vs 915nm vs 980nm vs 1064nm

Wavelength	General region	General characteristics	Treatment considerations
650nm	Visible red	More surface-oriented light delivery	Skin, wounds, superficial tissue
810nm	Near-infrared	Widely studied therapeutic wavelength	Muscle, joints, soft tissue
915nm	Near-infrared	Additional NIR treatment option	Soft tissue, rehabilitation
980nm	Near-infrared	Greater interaction with water	Soft tissue, therapeutic applications
1064nm	Near-infrared	Lower scattering characteristics	Deeper tissues, large animals

These are general optical characteristics rather than fixed clinical rules. The appropriate wavelength depends on the patient, target tissue, treatment objective, and complete treatment protocol.

 

Does a Higher Wavelength Always Mean Deeper Penetration?

Not necessarily.

It is common to simplify wavelength selection as:

650nm → superficial

810nm → deeper

1064nm → deepest

This can be useful as a basic concept, but actual light transmission through tissue is more complex.

Penetration and light distribution are affected by:

•  Wavelength

•  Tissue thickness

•  Tissue composition

•  Absorption

•  Scattering

•  Coat color

•  Skin pigmentation

•  Irradiance

•  Treatment geometry

•  Contact or non-contact application

 

Therefore, wavelength influences penetration potential but does not determine penetration by itself.

 

How Do Coat Color and Hair Affect Laser Transmission?

Veterinary patients have an additional consideration that is particularly important in laser therapy: hair and pigmentation.

Research in dogs has shown that wavelength, laser power, coat color, coat length, and shaving status can affect light transmission through tissue.

This means that the same laser setting may not deliver exactly the same amount of light through every animal.

Practical considerations may include:

•  Coat color

•  Hair length and density

•  Skin pigmentation

•  Treatment location

•  Whether the treatment area is clipped

•  Contact between the treatment head and skin

 

Where clinically appropriate, coat preparation and correct applicator positioning may help reduce superficial attenuation and improve consistency of light delivery.

 

Does Power Matter More Than Wavelength?

Neither should be considered in isolation. Power and wavelength describe different aspects of laser delivery.

Power (W) describes the rate at which optical energy is delivered.

Irradiance (W/cm²) describes power distributed over an area.

Energy (J) describes the total energy delivered:

Energy = Power × Time

Fluence (J/cm²) describes energy delivered per unit area.

Therefore, maximum power alone cannot determine the effectiveness of a veterinary laser.

Two systems with similar power can provide different tissue exposures because of differences in wavelength, spot size, treatment time, and application technique.

For more information, see Veterinary Laser Therapy Dosage: Power, Time & Area.

 

How Should Veterinarians Select a Wavelength?

A practical wavelength selection process can start with five questions:

1. What tissue is being treated?

Identify whether the target is primarily skin, muscle, joint, tendon, ligament, or another structure.

2. How deep is the target?

Consider the tissue thickness between the treatment surface and the intended target.

3. What is the patient like?

Species, body size, coat characteristics, pigmentation, and anatomical location can all affect treatment.

4. What is the clinical objective?

The objective may include rehabilitation, postoperative recovery, wound management, musculoskeletal treatment, or support of tissue recovery.

5. What is the complete treatment protocol?

Wavelength should be considered together with:

•  Power

•  Irradiance

•  Fluence

•  Treatment time

•  Treatment area

•  Application technique

•  Emission mode

• 
  

This approach is more useful than selecting a wavelength based only on the diagnosis.

 

Why Are Multi-Wavelength Lasers Useful?

Veterinary patients can have treatment targets at different anatomical depths.

For example, postoperative treatment may involve skin, subcutaneous tissue, muscle, and connective tissue. Rehabilitation may involve different structures depending on the animal, body size, and stage of recovery.

A multi-wavelength system provides clinicians with more flexibility when selecting light characteristics for different treatment objectives.

The advantage is therefore not simply the number of wavelengths available, but the flexibility to select or combine wavelengths according to the treatment target and clinical situation.For a broader treatment-planning perspective, see multi-wavelength laser therapy in veterinary rehabilitation.

 

Wavelength and Emission Mode

Wavelength is not the only factor that affects laser delivery.

Therapeutic laser systems may operate in:

l Continuous wave

l Pulsed mode

l Super pulsed mode

 

These modes change how optical energy is distributed over time.

Therefore, two treatments using the same wavelength can still produce different tissue exposures when power, treatment time, treatment area, or pulse characteristics are different.

 

Frequently Asked Questions

What wavelength is best for veterinary laser therapy?

There is no single best wavelength for every veterinary application. The appropriate choice depends on the target tissue, patient, clinical objective, and complete treatment protocol.

Does 1064nm penetrate deeper than 810nm?

1064nm has optical characteristics that may support light delivery to relatively deep treatment targets. However, actual light transmission depends on tissue composition, wavelength, treatment parameters, and application technique.

Is 650nm only for superficial tissues?

650nm is generally associated with more surface-oriented light delivery, but it should not be considered exclusively a skin-only wavelength.

Is higher laser power better?

Not necessarily. Higher power increases the rate of energy delivery, but treatment response also depends on wavelength, irradiance, fluence, treatment time, treatment area, and tissue condition.

Does coat color affect veterinary laser therapy?

Yes. Research in dogs has shown that coat color, coat length, shaving status, wavelength, and power can affect light transmission.

Why use a multi-wavelength veterinary laser?

Multi-wavelength systems provide greater flexibility when treating different tissues, anatomical depths, species, and clinical objectives.

 

Conclusion

Wavelength is a fundamental parameter in veterinary laser therapy because it influences how therapeutic light interacts with tissue.

However, wavelength should not be treated as a simple measurement of penetration depth. Actual light delivery depends on the interaction between wavelength, tissue properties, treatment parameters, patient characteristics, and application technique.

For veterinary professionals, the most useful approach is therefore not to ask which wavelength is universally best, but:

Which wavelength and treatment parameters are appropriate for this patient, target tissue, and clinical objective?

Understanding these principles can help veterinary professionals evaluate laser specifications, interpret research, and make more informed decisions when considering wavelength and other treatment parameters.

 

References

1. Hochman L. Photobiomodulation Therapy in Veterinary Medicine: A Review. Topics in Companion Animal Medicine. 2018;33(3):83–88.

2. Hochman-Elam LN, Heidel RE. Effects of laser power, wavelength, coat length, and coat color on tissue penetration using photobiomodulation in healthy dogs. Canadian Veterinary Medical Association. 2020;84(2):131–137.

3. Berrueta L, et al. A Systematic Literature Review of Complementary and Alternative Veterinary Medicine: Laser Therapy. Animals. 2023;13(4):667.

4. Bunch J. Photobiomodulation (Therapeutic Lasers): An Update and Review of Current Literature. Veterinary Clinics of North America: Small Animal Practice. 2023;53(4):783–799.