— —Pathologic analysis of the biologic effects and mechanisms of laser–tissue interactions requires correlation of the irradiation parameters with the biologic status and response of the target tissues over time. The photobiologic mechanisms of laser-induced tissue injury can be separated into three categories, photochemical, photothermal and photomechanical. Anatomic pathologic analysis of laser-induced lesions reveals alterations that represent either specific markers of the photobiologic mechanism or non-specific reactions to tissue injury. Repair, regeneration and wound healing of laser induced lesions appear to be non-specific responses to the type of tissue damage rather than the photobiologic mechanism producing the lesion.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1751-1097.1991.tb09897.x

Pathologic analysis of photothermal and photomechanical effects of laser-tissue interactions.

Hemangiomas are the most common soft-tissue tumors of infancy, occurring in approximately 5 to 10 percent of one-year-old children. Despite the frequency of these tumors, their pathogenesis is not completely understood, and the best approach to their management remains controversial. Research on angiogenesis, an improved knowledge of the classification of the vascular anomalies of infancy, advances in imaging techniques, recently identified complications, and new therapeutic approaches, such as treatment with interferon and lasers, have altered our understanding of this common childhood problem and the way we approach it. The term hemangioma has traditionally been applied to a variety of vascular . . .

https://www.nejm.org/doi/pdf/10.1056/NEJM199907153410307

Hemangiomas in Children

Laser-tissue interactions

Thirty-five children, three months to 14 years of age, with disfiguring port-wine stains were treated with a flashlamp-pulsed tunable dye laser. All had complete clearing of the stains after an average of 6.5 laser treatments to each lesional area; skin over bony prominences required approximately half as many sessions as skin on the cheek. Children less than seven years old required fewer sessions (mean ±SD, 5.8±1.1) than older children (7.1±1.1; P<0.05). Treated skin was identical in texture and color to adjacent normal skin in 33 (94.3 percent) of the children, whereas 2 (5.7 percent) had small, isolated, depressed scars in areas accidentally traumatized soon after laser treatment. The only other side effect was transient hyperpigmentation, which occurred in 20 patients (57 percent). These results can be attributed to two distinguishing characteristics of the flashlamp-pulsed tunable dye laser: an emission wavelength of 577 nm, theoretically ideal for selective absorption by the intravascular ...

Treatment of children with port-wine stains using the flashlamp-pulsed tunable dye laser.

https://www.jidonline.org/article/0022-202X(89)90079-1/pdf

Selective photothermolysis of cutaneous pigmentation by Q-switched Nd: YAG laser pulses at 1064, 532, and 355 nm.

Action spectrum of vascular specific injury using pulsed irradiation.

Of 310 patients with port-wine stains, 68% had more than one dermatome involved; 85% had unilateral and 15% had a bilateral distribution of their port-wine stain. At the time of examination, 8% of all patients with trigeminal port-wine stains had evidence of eye and/or central nervous system (CNS) involvement. Extensive involvement, with port-wine stain over the trunk and extremities as well as the head and neck, was observed in 12%. Patients who did not have port-wine stains on the areas served by branches V1 and V2 of the trigeminal nerve had no signs or symptoms of eye and/or CNS involvement. Port-wine stains of the eyelids, bilateral distribution of the birthmark, and unilateral port-wine stains involving all three branches of the trigeminal nerve were associated with a significantly higher likelihood of having eye and/or CNS complications. Twenty-four percent of those with bilateral trigeminal nerve port-wine stains had eye and/or CNS involvement compared with 6% of those with unilateral lesions. All those who had eye and/or CNS complications had port-wine stain involvement of the eyelids; in 91% both upper and lower eyelids were involved, whereas in 9% only the lower eyelid was involved. None of those with upper eyelid port-wine stains alone had eye and/or CNS complications. In addition, 3 (75%) of the 4 subjects with seizures alone had bilateral port-wine stain involvement. A third group, these with unilateral V1, V2, and V3 port-wine stains, had eye and/or CNS complications in 3 (19%) of 16 subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Location of Port-Wine Stains and the Likelihood of Ophthalmic and/or Central Nervous System Complications

Although the flashlamp-pulsed-dye laser has been successfully used for the treatment of port-wine stains (PWS) at 577 nm, a number of adult patients had incomplete clearance of their birthmarks with this treatment modality because of residual vessels lying beyond the 0.75-mm penetration depth of 577-nm irradiation. Fifteen adult patients, of whom nine were previously treated with limited success at 577 nm (group A), and six untreated patients (group B) were included in the study. For the group A patients, treatment with 585 nm produced successful clearance of the birthmark. For the six patients in group B, parallel treatment of different sites of the same lesion coupled with skin biopsies and histologic examination revealed that a change in the wavelength from 577 to 585 nm allowed the laser light to penetrate from the midreticular dermis into the subcutaneous fat. This explained the clearance achieved at 585 nm and not at 577 nm.

Oon Tian Tan

Papers

Treatment of children with port-wine stains using the flashlamp-pulsed tunable dye laser.

Action spectrum of vascular specific injury using pulsed irradiation.

Location of Port-Wine Stains and the Likelihood of Ophthalmic and/or Central Nervous System Complications

585 nm for the treatment of port-wine stains.

Effect of wavelength on cutaneous pigment using pulsed irradiation