Intense Pulsed Light: A Methodical Approach to Understanding Clinical Endpoints

February 2021 | Volume 20 | Issue 2 | Case Reports | 203 | Copyright © February 2021


Published online January 10, 2021

Michael B Lipp DO, Kunal Angra MD, Douglas C Wu MD PhD, Mitchel P Goldman MD

Cosmetic Laser Dermatology: A West Dermatology Company, San Diego, CA

Abstract
Background: Intense Pulsed Light (IPL) is a non-coherent polychromatic broadband filtered flashlamp that emits light in the spectrum of approximately 400–1200 nm. Its effects on photorejuvenation are well documented. The goal of this study is to help practitioners better conceptualize and fine tune IPL device settings in order to produce the most effective and safest clinical outcome.
Materials/Methods: This was a prospective study testing several filters (515 nm; 560 nm; 590 nm and 530–650; 900–1200 nm vascular filter), fluences, pulse durations, and pulse numbers (ie, multiple sequence pulsing or MSP) with a new IPL system.
Results: Post-procedure erythema response was more pronounced with increasing fluence, decreasing wavelength, fewer pulses and shorter pulse duration. The exception was the 515 nm filter with regard to pulse duration, which was observed to have a more pronounced response with longer pulse durations. The overall clinical outcome at the 4-week follow-up visit demonstrated greatest improvement in erythema and pigmentation using the 515 nm filter on a Fitzpatrick Skin Type III individual.
Conclusion: Greatest clinical endpoint response at 4-week follow-up was observed with more robust initial responses. This was most apparent at higher fluence levels and fewer pulse counts. However, when the IPL is pushed to aggressive parameters, there is risk of hypopigmentation and hair loss as seen in this case study. Skin type is an important consideration when using IPL and MSP adds to its safety profile.

J Drugs Dermatol. 20(2):203-207. doi:10.36849/JDD.2020.5638
Intense Pulsed Light (IPL) is a non-coherent polychromatic broadband filtered flashlamp that emits light in the spectrum of approximately 400–1200nm. Cut-off filters are placed over the window of an optical treatment head or embedded into a quartz or sapphire light guide to block wavelengths lower than the filter. Cut-off filters allow for preferential selection of various chromophores including melanin (400–755 nm), oxyhemoglobin (600–630 nm; peaks 418, 542, and 577 nm) and deoxyhemoglobin (600–750 nm). They can also be selected to adjust for both depth of penetration and different skin types.

Originally developed to treat leg telangiectasias,1 IPLs soon found other applications including other types of vascular lesions, hair removal, destruction of benign pigmented lesions, and overall photorejuvenation.2-10 One of the main advantages of the IPL is its ability to simultaneously treat both benign pigmented lesions such as solar lentigines and ephelides, as well as vascular lesions such as telangiectasia and erythema with minimal to no patient downtime. In addition, histologic analysis of the papillary and reticular dermis has shown that dermal heat produced from IPL treatments induce new collagen production.11-14 This may account for the improved skin texture, fine wrinkles and pore size.15 The combination of beneficial effects has been termed “photorejuvenation”.16,17

IPLs typically feature integrated cooling via filtered cooling crystals.14 A thin layer of chilled transparent water-based gel is applied to the skin for optical coupling with the crystal, allowing for optimal transmission of light by decreasing the refractive index of light to the skin. Cold-air cooling can also be applied during the treatment to enhance patient comfort. Studies have demonstrated increased thermal protection of the epidermis, allowing use of higher fluence parameters (15–30%) while reducing side effects.18

Numerous IPL devices exist in the current marketplace, and each has a unique set of parameters; thus, the efficacy and safety profile may not be reproducible between devices. In general Fitzpatrick skin types I–III can be safely treated with a 560 nm filter while skin types IV–V are often treated with longer wavelength filters. Correction of red vascular lesions and erythema where oxygenated hemoglobin predominates can be achieved by using 515–590 nm cut-off filters while blue vascular lesions or purpuric patches where deoxygenated hemoglobin predominates are better targeted with filters of 590 or higher.

IPLs emit pulse durations in the millisecond range, which is longer than the thermal relaxation time (TRT) of melanosomes (TRT is ~200–400 nanoseconds). However, reports have