What are the best parameters to adjust to improve outcomes for patients when using pulsed light? How do we maintain safety, yet ensure we are delivering the most comprehensive treatments?
You may be asking: why don’t my recommended protocols deliver consistently on every patient? Different equipment manufacturers will utilise their own recommended parameter settings for varying indications when it comes to vascular and pigmented. The commonality across all pulsed light devices is physics. What I mean by this is, regardless of the pulsed light modality you are using in your practice, the following advice will be relevant and applicable to help optimise the outcomes you are achieving with your treatments and are therefore the fundamentals of pulsed light treatments.
I consider the five most important factors for enhanced patient outcomes using pulsed light treatments are:
1. Spot Size
What is it?
Spot size determines the treatment area and is where the headpiece’s treatment window makes contact with the skin.
Why is it important?
The contours of the area you are looking to treat should always be considered with the most suitable spot size, to ensure the best contact in the
treatment zone. Lack of contact can lead to adverse events, which often can be avoided with appropriate spot sizes.
How can I use this to my advantage?
If treating a forehead, nose or the area around the mouth, it is better to treat with a smaller spot size. For example, if you use a spot of 15mm x 15mm, this will ensure best contact with the contours of the forehead. This is opposed to larger spot sizes, which will give better surface contact on the broader more fleshy areas. Additionally, some platforms o er smaller treatment areas, between 7-11mm to ensure high energy delivery to spot treat indications, without potentially compromising skin across the whole window.
2. Fluence
What Is It?
Fluence is the energy delivered per unit area and is measured in joules per square centimetre. So the power of 1 watt is equivalent to 1 joule per second, though typically pulsed light devices opt for a measure of fluence on the screen.
Why is it important?
Fluence will determine how much output energy is delivered to ensure adequate absorption into the targeted chromophore (along with the correct wavelength and pulse duration). Fluence selection will be subject to Fitzpatrick skin type, with higher fluence on lighter skin, and lower fluence on darker skin. Additionally, when treating with pulsed light ‘o face’, you would typically use 1 to 2 joules less than the facial settings, due to increased sun exposure in that area.
How can I use this to my advantage?
Ability to specifically adjust fluence will enhance patient outcomes, so adjustment of this parameter is essential. Typically, increasing fluence by 1 joule is the first step and preferred option when looking to treat pigmentation. Try a test patch with your recommended settings, then try +1 joule for a comparison on skin reaction. Keep in mind that 1 joule of fluence is a big increment with pulsed light, so be careful.
3. Wavelength
What is it?
Wavelength (measured in nanometers) will determine the depth of penetration of the pulsed light. Think of it like a tinted window; the darker the tint,
the less the light will pass through.
The lighter the tint, the further it will penetrate. Pulsed light wavelength cut-off filters typically range from 420nm through to 800nm. Remember, the lower the nm rating, the more aggressive; so always consider your energy settings and target.
Why is it important?
Wavelength cut-off filters allow more specific absorption in the preferred chromophore. Determining the correct filter should always be considered when deciding what chromophore you intend to treat for the best efficacy.
For example, a 515nm wavelength is optimal to treat pigmentation, as this is more super cial than vascular (560nm) or hair (590-695nm). This is directly in line with the laser absorption scale. At the wavelength of 515nm, you will see the best isolation for the melanin chromophore with the least con ict from the vascular targets. The same can be said for the 560nm for vascular; there is less con ict with pigment at this wavelength. (Note we would use longer wavelength when treating darker Fitzpatrick skin types.)
How can I use this to my advantage?
Assuming that using a 590nm wavelength should have some efficacy on both pigment and vascular targets is correct. After all, the light will be absorbed in both. One of
the most common treatments performed in light-based clinics is a ‘one pass treatment’ for photo rejuvenation. Physics tells us this
is in fact a sub-optimal approach to treatment for patients. A more clinically efficient approach would be to treat (on separate occasions, four weeks apart) pigment and vascular independently – starting with the dominant chromophore first. This ensures the highest level of concentrated energy is delivered selectively into specific targets.
4. Pulse Duration
What is it?
Pulse duration (measured in milliseconds or ms) is the amount of time the light is on for the pulse.
Why is it important?
This is another critical parameter that should be fully adjustable on a pulsed light system for best practice. Lets say we have two options to treat a vascular patient. If we have a treatment setting at 15 j/cm2, with a 20ms pulse duration and another treatment setting at 15 j/cm2 with a 10ms pulse, which one is going to allow the highest level of energy into to the target, and why? Both are the same fluence. The 20ms option, will deliver 15 joules to the target in 20ms. If we deliver the same amount of energy, in a shorter timeframe (10ms) this will have a faster temperature rise, as it allows the target less time to cool, providing a more efficient energy absorption.
How can I use this to my advantage?
Try shortening the pulse duration (instead of increasing fluence) when treating vascular indications. Shortening the pulse duration by 5ms from your recommended protocols can have a more prominent impact than increasing joules. If the skin is still responding safely but you’re not achieving the desired result, consider adding another j/cm2 for that ‘wow’ result.
5. Cooling
What is it?
There are many methods of cooling with light-based devices.
The most common with pulsed light devices is direct contact cooling. This means the immediate treatment area will be cooled, to protect the epidermis when the light is delivered to the skin. In my opinion, sapphire tips are the preferred option in pulsed light systems as sapphire is more conductive and doesn’t pit.
Why is it important?
Safety and comfort! If we don’t cool the epidermis, we are not able to deliver high energy levels safely to the target chromophores without risk of burns. However, having the temperature too cold can also obstruct efficient temperature rise of the target chromophore. Let’s consider treating a patient for pigment. If you use cooling at 3 degrees Celsius (on a Fitzpatrick skin type 2) with 12 joules and a 10ms pulse, you can be con dent this is highly efficient to manage patient safety. Unfortunately, this means the temperature of the target chromophore will also be much lower. Therefore, heat to the target from energy output is compromised by over cooling, and this jeopardises results. Remember, the body’s average temperature should be around 37 degrees Celsius. To ensure safe cooling for the skin, while balancing effective temperature rise in our target, an optimal temperature for contact cooling should be 15-25 degrees.
How can I use this to my advantage?
Sometimes it can be di cult to achieve the desired response when adjusting fluence or pulse duration alone. I recommend trying to increase the temperature; usually +4 to 5 degrees to ensure a better absorption to the target chromophore, with less cooling conflict for lighter skin types. For darker skin types, try reducing the cooling, and increasing pulse duration (and energy if needed). This allows delivery of more energy, more safely to darker skin types.
With an understanding of these 5 key factors of pulsed light, we can refine our approach to treating patients and, in time, use all 5 of these factors together to create highly bespoke treatment plans for every patient and deliver the best outcomes, more safely and effectively every time. AMP
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