Safety & Skin Types
Yellow (577nm) is a photoselective wavelength that targets blood vessels with minimal impact on skin pigment. Hence, professionals can now safely treat both a broader range of skin skin types (I to V, including Asian, Middle Eastern and South American skin types).
"Selective photothermolysis" ensures effective injury to targeted lesions, while avoiding damage to healthy skin tissue. Targeted chromophores within tissue (e.g. water, haemoglobin / blood, melanin / pigment) absorb light at different wavelengths more or less effectively.
For targeting haemoglobin (Hb, or blood), Dermatologists have long recognized 577nm as the ideal wavelength for treatment of vascular lesions. And until the advent of 577nm lasers, green lasers (532nm) represented the standard of care.
Yellow (577nm) is primarily absorbed by haemoglobin; whereas, green (532nm) is equally absorbed by both haemoglobin and melanin (chart below). Melanin absorption increases risk of post-inflammatory hyperpigmentation (PIH). Hence, green laser treatments of patients with dark skin types IV to VI are contraindicated. And people with Asian skin and skin type III must be carefully treated.
Chart: Absorption of wavelength by skin structure.
Although limited in scope, 532nm lasers are preferred for removal of benign, superficial pigmented lesions where both haemoglobin and melanin are primary targets.
For selective photothermolysis of haemoglobin, 577nm laser technology is a safer alternative, with fewer side effects for both light and dark skin types (I to V).