Treatment Room Reference Guide

Laser & IPL
Quick Reference

Essential parameters, safety rules, chromophore targets, skin types, contraindications, and key formulas — everything you need at a glance.

Based on Murphy & Torstensson — The Laser-IPL Guys

⚠ The Most Critical Parameter

Energy Density (Fluence)

The amount of energy delivered per unit area. Understanding this is ABSOLUTELY CRITICAL before treating any patient.

Fluence (J/cm²) = Energy (J) ÷ Spot Area (cm²) RADIANT EXPOSURE · Must be verified before every treatment

Fluence Quick-Calc (Circular Spot)

Spot Ø (mm)	Multiply Joules by	Example (0.5 J)
3	14.1	7.1 J/cm²
4	8.0	4.0 J/cm²
5	5.1	2.5 J/cm²
6	3.5	1.8 J/cm²
7	2.6	1.3 J/cm²
8	2.0	1.0 J/cm²
10	1.27	0.6 J/cm²

e.g. 0.4 J into 6 mm spot → 0.4 × 3.5 = 1.4 J/cm²

Parameter Definitions

Wavelengthnm	Distance between wave peaks. Determines which chromophore is targeted.
Pulse Durationms / µs / ns	How long the light pulse lasts. Must be ≤ TRT of target for selective damage.
Spot Sizemm	Diameter of the beam. Larger spots penetrate deeper; smaller = higher fluence for same energy.
PowerWatts (W)	Rate of energy delivery. Power (W) = Energy (J) ÷ Time (s)
Power DensityW/cm²	How fast fluence is delivered. Short pulses → very high power density.
Rep RateHz	Number of pulses per second. Higher rate = faster treatment coverage.
Pulse Train—	A sequence of pulses fired in rapid succession. Common in IPL systems.

Thermal Relaxation Time (TRT)

The time for a target to lose 50% of its heat to surrounding tissue. Pulse duration should be ≤ TRT for selective injury.

Melanosomes~1 µs	Very fast cooling — use short pulses.
Hair follicle~40–100 ms	Slow cooling — longer pulses acceptable.
Blood vessel~1–10 ms	Depends on vessel diameter.
Tattoo ink~10 ns	Extremely fast — requires Q-switched lasers.

Selective Photothermolysis — The Core Principle

Match the wavelength of light to the absorption peak of the target chromophore, use a pulse duration ≤ TRT, and deliver sufficient fluence — to heat the target selectively without damaging surrounding tissue.

400 nm (UV)700 nm1100 nm (NIR)

        ←  Visible Light  →
        Near-Infrared →
      

Melanin (Hair & Pigmentation)

Best wavelengths	694 nm (Ruby) · 755 nm (Alex) · 810 nm (Diode) · 1064 nm (Nd:YAG)
IPL range	500–950 nm with appropriate cut-off filters
Notes	Eumelanin absorbs strongly in 400–700 nm. Darker hair = better absorption. Lighter skin = safer margins.
Pulse duration	Hair removal: 10–100 ms · Pigmented lesions: 2–20 ms

Oxyhaemoglobin (Vascular)

Best wavelengths	532 nm (KTP) · 577–585 nm · 595 nm (PDL) · 1064 nm (deep vessels)
IPL range	515–600 nm (superficial) · 590–950 nm (deeper)
Notes	Oxy-Hb has strong absorption at 418, 542 & 577 nm. Vessel depth determines wavelength choice.
Pulse duration	Small telangiectasia: 1–3 ms · Leg veins: 10–50 ms

Tattoo Ink (Multi-colour)

Black / dark	1064 nm (Nd:YAG) · 694 nm (Ruby)
Red	532 nm (KTP/frequency-doubled Nd:YAG)
Blue / green	694 nm · 755 nm (Alexandrite)
Yellow / orange	Difficult — 532 nm may help
Pulse duration	Must be in nanoseconds (Q-switched) or picoseconds — ink particles have ~10 ns TRT

Common Aesthetic Laser Wavelengths

532 nm KTP	Vascular, red tattoo, superficial pigment
585 / 595 nm PDL	Pulsed dye — vascular lesions, rosacea, PWS
694 nm Ruby	Hair, pigment, blue/black tattoo
755 nm Alexandrite	Hair (light–medium skin), tattoo (blue/green)
800–810 nm Diode	Hair removal (all skin types if cooled)
1064 nm Nd:YAG	Deep vascular, dark tattoo, hair (darker skin)
2940 nm Er:YAG	Ablative skin resurfacing (water absorption)
10,600 nm CO₂	Ablative resurfacing — very strong water abs.

Water (Ablative Targets)

Best wavelengths	2940 nm (Er:YAG) · 10,600 nm (CO₂)
Target	Water in skin cells — used for resurfacing, wrinkle reduction, lesion removal
Notes	CO₂ = more thermal damage / collagen stimulation. Er:YAG = more precise ablation, faster healing.

Remember: The chromophore must absorb the wavelength used. Always check absorption spectra for your target. IPL uses a broad spectrum (typically 500–1200 nm) with cut-off filters to select the desired range.

Fitzpatrick Scale — At a Glance

Type	Appearance	Sun Response	Melanin Level	Laser/IPL Risk	Key Considerations
I	Very pale / ivory	Always burns, never tans	Very low	LOW	Widest treatment margins; minimal competing epidermal melanin
II	Fair / beige	Usually burns, tans minimally	Low	LOW	Good candidate for most treatments; still caution with high fluences
III	Medium / olive	Sometimes burns, tans gradually	Moderate	MODERATE	Reduce fluence; use longer wavelengths; avoid recent sun exposure
IV	Olive / light brown	Rarely burns, tans easily	Moderate–high	MODERATE	Higher PIH risk; use 1064 nm; test patch essential; active cooling required
V	Brown	Very rarely burns, tans darkly	High	HIGH	Significant PIH risk; only 1064 nm Nd:YAG or specialist diode; longer pulses essential
VI	Deep brown / black	Never burns	Very high	HIGH	Most challenging; experienced practitioner only; risk of burns, scarring, PIH/PIH; 1064 nm preferred

⚠ PIH — Post-Inflammatory Hyperpigmentation

Melanin-rich skin (Types IV–VI) is at significant risk of PIH following laser/IPL. The epidermal melanin competes with the target chromophore — absorbing energy and overheating.

Always perform a test patch 4–6 weeks before treatment
Avoid treatment on recently tanned skin
Use the longest appropriate wavelength
Apply active cooling (contact, cryogen spray, or cold air)
Reduce fluence significantly for darker types

Wavelength Selection by Skin Type

Types I–III	Most wavelengths suitable. Start conservatively.
Type III–IV	Prefer 755–810 nm for hair; reduce visible wavelengths
Type IV–V	1064 nm Nd:YAG preferred; avoid 532–694 nm
Type V–VI	1064 nm only, with aggressive cooling & low fluence

Tanning — Key Rule

A tan increases epidermal melanin in Fitzpatrick Types I–IV, effectively shifting them toward darker types. Do not treat recently tanned skin. Wait 4–6 weeks post-sun/sunbed exposure. Sunscreen advice is mandatory pre- and post-treatment.

The Four Main Photoreactions

⚡ Photo-thermal

Light energy is absorbed and converted to heat. The most common mechanism in aesthetic lasers. Basis of Selective Photothermolysis. Degree of damage depends on temperature reached and duration.

💥 Photo-mechanical (Photoacoustic)

Ultra-short pulses (ns/ps) create rapid thermal expansion → shockwaves. Primary mechanism in tattoo removal with Q-switched/picosecond lasers. Shatters ink particles mechanically.

✂ Photo-ablation

High-fluence UV/IR energy breaks molecular bonds directly, vaporising tissue layer by layer. Used in CO₂ and Er:YAG resurfacing. Requires precise fluence control.

🔆 Photo-chemical (PDT)

Light activates a photosensitising agent (e.g. ALA), producing reactive oxygen species that destroy target cells. Used in photodynamic therapy for acne, pre-cancerous lesions.

What Happens to Light in Skin

Reflection	~4–7% reflected at skin surface. Higher for darker skin (back-scattering). This energy never reaches the target.
Scattering	Photons collide with dermal structures and change direction. Causes beam spread with depth. Can redirect photons back out of skin (back-scatter).
Absorption	Photon energy is transferred to the absorbing molecule (chromophore), causing heating. Probabilistic — even weak absorbers absorb some photons.
Transmission	Photons that pass through without absorption or scattering. Longer wavelengths penetrate deeper (less scatter).

Depth rule of thumb: Longer wavelength → deeper penetration. 532 nm targets superficially; 1064 nm reaches deep dermis and subcutaneous vessels.

Treatment Applications Quick Ref

Hair removal	Target: melanin in follicle bulge/bulb. Wavelength: 755–1064 nm. Pulse: 10–100 ms. Multiple sessions (hair cycle).
Vascular lesions	Target: oxyhaemoglobin. Wavelength: 532–1064 nm. PDL 595 nm gold standard for PWS. Coagulation endpoint.
Pigmentation	Target: epidermal/dermal melanin. Wavelength: 532–755 nm. Short pulses. Test patch critical for darker types.
Tattoo removal	Target: ink particles. Q-switched (ns) or pico (ps) lasers. Multiple sessions. Ink colour determines wavelength.
Skin rejuvenation	Non-ablative: sub-threshold heating of dermis. Ablative (CO₂/Er:YAG): vaporises epidermis, stimulates collagen.
Acne	PDT, IPL (420–950 nm), or 1450 nm diode. Targets sebaceous glands and P. acnes porphyrins.

Laser vs IPL — Key Differences

LASER

Single wavelength (monochromatic)
Coherent, collimated beam
Very precise target matching
Higher peak powers possible

IPL

Broad spectrum (500–1200 nm)
Filtered to select range
More versatile, less selective
Larger treatment areas

⚠ Class 4 Warning

All medical/aesthetic lasers are Class 4 (output > 500 mW). They can cause permanent eye injury — including blindness — from direct, reflected, or scattered beams. Appropriate eye protection is MANDATORY for all persons in the treatment room.

International Laser Classification (IEC 60825-1)

Class	AEL Limit	Hazard Level	Examples / Notes
Class 1	< 0.039 mW	Safe under all conditions	CD players, printers. Laser is enclosed.
Class 1M	< 0.039 mW	Safe without optical aids	Dangerous if viewed through lens/binoculars.
Class 2	< 1 mW	Low risk — blink reflex protects	Visible lasers only. Barcode scanners.
Class 3R	< 5 mW	Small risk if viewed directly	Laser pointers. Avoid direct eye exposure.
Class 3B	< 500 mW	Hazardous — direct or specular reflection	Research/display lasers. Eyewear required.
Class 4	> 500 mW	Severe hazard — all reflections dangerous	All medical/aesthetic lasers. Burns skin and eyes. Eyewear mandatory. Fire risk.

Optical Density (OD) — Eye Protection

OD is the logarithmic measure of light attenuation by safety glasses. The higher the OD, the more protection provided.

OD = log₁₀(Incident Power ÷ Transmitted Power) OD 4 = blocks 99.99% · OD 5 = blocks 99.999%

OD Value	Attenuation Factor	% Blocked
OD 1	10×	90%
OD 2	100×	99%
OD 3	1,000×	99.9%
OD 4	10,000×	99.99%
OD 5	100,000×	99.999%
OD 6	1,000,000×	99.9999%

Glasses must be rated for the specific wavelength of your laser. Check the markings on the frame. OD alone is not sufficient — wavelength range must match.

⚠ Eyewear Rules — Non-Negotiable

Operator, patient AND any observer must wear appropriate eyewear
Glasses must match the laser wavelength AND be rated for pulsed outputs
IPL requires dedicated IPL goggles — laser glasses are NOT equivalent
Patient eye shields (internal) required for periorbital treatment
Inspect eyewear before every session — discard if damaged
Never rely on ordinary sunglasses

NOHD — Nominal Ocular Hazard Distance

The distance within which the beam intensity exceeds the MPE for the eye. Anyone inside the NOHD must wear appropriate laser safety eyewear. For a 1 W Class 4 laser with low divergence, NOHD can exceed 200 metres.

Room rule: Assume the NOHD covers the entire treatment room. All persons present must wear appropriate eyewear whenever the laser is armed or firing.

Absolute Contraindications

Do NOT treat if any of these are present:

Active infection / open wounds in treatment area

Photosensitising medications (e.g. tetracyclines, isotretinoin within 6 months)

Known photosensitivity disorders (e.g. lupus, porphyria)

Active herpes simplex in treatment zone

Pregnancy (ablative & most treatments)

Undiagnosed pigmented lesions — refer for dermatology review

Fitzpatrick V–VI without specialist training & appropriate equipment

Epilepsy triggered by flashing lights (IPL)

Current or recent radiotherapy to the area

Active vitiligo in treatment zone

Cautions — Assess & Discuss

Recent sun/sunbed exposure — wait 4–6 weeks, ensure SPF50 compliance
Anticoagulants (aspirin, warfarin) — increased bruising/purpura risk
Diabetes — impaired wound healing; lower fluence, monitor closely
Gold implants (RF devices) — avoid over implant area
Tattoos in treatment field — risk of pigment explosion
History of keloid/hypertrophic scarring — approach cautiously
Immunosuppressive medications — slower healing, increased infection risk
Fitzpatrick III–IV — require test patch, reduced fluence, cooling
PCOS / hormonal imbalance — affects hair removal outcomes
Botulinum toxin or fillers recently — delay 2–4 weeks

Pre-Treatment Session Checklist

Consent form signed and dated
Medical history form reviewed & updated
Contraindications and cautions confirmed absent or documented
Test patch performed and reviewed (if required)
Fitzpatrick type assessed
Area free of makeup, creams, deodorant
Treatment area shaved (hair removal) or appropriate prep completed
Recent sun exposure / tan confirmed absent

Equipment calibration verified and log checked
Correct wavelength / handpiece selected for treatment
Parameters (fluence, pulse duration, spot size) set and confirmed
Operator eyewear (correct OD & wavelength) worn
Patient eyewear / shields fitted
Laser warning signs displayed, door locked / controlled
Cooling system checked and active
Treatment notes and parameters recorded

⚠ Designated Laser Room Requirements

Door must be locked or controlled during treatment — no unauthorised entry
Warning signs posted on all entry points (laser type, wavelength, class)
Windows covered / blacked out to prevent external beam escape
Non-reflective surfaces (matte) on walls, instruments, and fittings in beam path
No flammable materials or oxygen supplies near beam
Fire extinguisher accessible
Appropriate eyewear for each laser wavelength readily available at entry
Emergency stop / key-switch accessible to operator at all times

Plume & Air Quality

Laser/IPL treatment of tissue generates a smoke plume containing particulates, toxic gases (CO, HCN, benzene) and viable biological material. This is a documented health hazard.

Dedicated smoke evacuator with HEPA & activated carbon filtration required
Nozzle positioned 1–2 cm from treatment site
Surgical masks are insufficient — appropriate respirators recommended for ablative procedures
Room ventilation should be verified regularly

Multiple Lasers in One Room

Each laser requires its own appropriate safety eyewear — do not mix
Label each pair of glasses clearly with wavelength
Only one laser should be armed and ready at any time
Interlock systems should prevent simultaneous operation

Essential Glossary

Absorption Transfer of photon energy to a molecule, raising it to an excited state — converted to heat.

AEL Accessible Emission Limit — the maximum permitted emission for each laser class.

Chromophore A molecule that selectively absorbs a specific wavelength of light (e.g. melanin, haemoglobin, water, tattoo ink).

Coherence All photons in a laser beam are in phase — a unique property distinguishing lasers from other light sources.

Fluence Energy density, measured in J/cm². The most critical treatment parameter.

MPE Maximum Permissible Exposure — the highest level of laser radiation to which the eye or skin can be exposed without harm.

NOHD Nominal Ocular Hazard Distance — within which beam intensity exceeds MPE; eyewear mandatory.

Optical Density (OD) Log₁₀ measure of protective eyewear attenuation. Must match wavelength.

Photothermal Light converted to heat in tissue. Principal mechanism of most aesthetic laser treatments.

PIH Post-Inflammatory Hyperpigmentation — darkening of skin after trauma, especially in darker skin types.

Scattering Redirection of photons as they travel through tissue, reducing penetration depth and spreading energy.

Selective Photothermolysis Matching wavelength to chromophore + pulse ≤ TRT = selective heating of target without collateral damage.

TRT Thermal Relaxation Time — time for target to lose 50% heat. Pulse duration must be ≤ TRT.

Wavelength Distance between wave peaks, measured in nm. Determines penetration depth and chromophore target.

Calibration — Why It Matters

A laser or IPL that is not correctly calibrated may be delivering significantly different fluence than the display shows — higher or lower. Treating with a miscalibrated machine is potentially dangerous.

Always verify calibration before treating patients
Use a calibrated power/energy meter at regular intervals
Learn to read and interpret your calibration chart — actual output vs. set output
Document calibration checks in your equipment log
If actual output differs materially from set value, do not use the machine — contact manufacturer

Analogy: Driving with a faulty speedometer is dangerous — the reading isn't what you think. Same applies to an uncalibrated laser.

Spot Size Effect on Fluence & Penetration

Halving the spot diameter quadruples the fluence for the same energy output
Doubling the spot diameter quarters the fluence
Larger spot sizes allow deeper penetration due to reduced scattering at the edges
Always recalculate fluence when changing handpieces or spot sizes

Area (cm²) = π × (r in cm)² r = half the spot diameter · 1 cm = 10 mm · 1 mm = 0.1 cm

One-Page Treatment Decision Guide

Step 1	Identify the target chromophore (melanin / Hb / water / ink)
Step 2	Select wavelength that matches chromophore absorption peak
Step 3	Assess Fitzpatrick type — adjust wavelength and fluence accordingly
Step 4	Choose pulse duration ≤ TRT of the target structure
Step 5	Calculate fluence for chosen spot size — verify calibration
Step 6	Check all contraindications; complete pre-treatment checklist
Step 7	Ensure eyewear correct for wavelength — operator, patient, observers
Step 8	Perform test patch if new patient, new parameters, or darker skin type
Step 9	Treat conservatively — it is easier to do more than to undo damage
Step 10	Document all parameters, patient response, and any adverse reactions

⚠ If You Are Uncertain

If you are unsure about any parameter, the patient's suitability, the machine's calibration, or an unusual skin response — stop and seek advice before proceeding. The consequences of incorrect laser/IPL treatment can be permanent. "When in doubt, don't" is a sound clinical principle.

FURTHER READING

For full explanations of all concepts in this booklet, refer to the complete eBook: An Introduction to Medical/Aesthetic Lasers and IPL Systems by Michael J. Murphy & Per-Arne Torstensson (The Laser-IPL Guys). Available at online.flipbuilder.com/rbhw/bwhw

⚡

Laser & IPLQuick Reference

Energy Density (Fluence)

⚡ Photo-thermal

💥 Photo-mechanical (Photoacoustic)

✂ Photo-ablation

🔆 Photo-chemical (PDT)

LASER

IPL

⚠ Class 4 Warning

Laser & IPL
Quick Reference