Laser Therapy for the Treatment of Telangiectasias and Reticular Veins in the Lower Extremity
- Joseph J. NaoumEmail Joseph J. Naoum
- Abdalrahman Ahmed Alghendy
Introduction: Principles of Laser Therapy
The term laser is an acronym for light amplification by stimulated emission of radiation. A typical laser emits light in a narrow, low-divergence monochromatic beam with a well-defined wavelength. Therapeutic effects are the result of a combination of unique laser properties and complex laser/tissue interactions. For a clinical effect to take place, laser light must be absorbed by chromophores such as water, melanin, and oxyhemoglobin in the case of vascular lesions. Each chromophore preferentially absorbs a specific wavelength of the laser light. When laser light is absorbed by the target chromophores, it has a photochemical, photothermal, and photomechanical effect1 on tissues.
The output energy of the laser is referred to as the energy density or fluence and is measured in joules/centimeter squared (J/cm2). The depth of penetration of the laser light depends on its wavelength. Increasing the wavelength will lead to an increase in the depth of penetration and a decrease in scattering, which is more prevalent in the dermis due to its high collagen content. Thermal destruction of a target lesion can be achieved without damage of the surrounding normal tissue.2 To achieve selective photothermolysis, three basic elements must be considered: 1) selection of a wavelength of light that is preferentially absorbed by the intended tissue target, which in the case of vascular lesions is oxyhemoglobin; 2) the pulse duration of the laser, or the exposure time of the tissue to the laser energy, must be shorter than or equal to the chromophore’s thermal relaxation time (defined as the time required for the targeted site to cool to one-half of its peak temperature immediately after laser irradiation); and 3) the energy density delivered by the laser must be sufficient to irreversibly damage the target within the allotted time.3 In this manner, the laser parameters can be adjusted to target specific vascular lesions, leading to their maximal destruction with minimal damage to the surrounding tissues.
The need for epidermal protection to avoid collateral damage to basal keratinocytes prompted the development of epidermal cooling devices.4, 5 Selective cooling of the epidermis has been shown to minimize epidermal injury and can be achieved by using various systems. Chill tips, cooled glass chambers, sapphire windows, cold sprays or halogenized hydrocarbons, liquid nitrogen, and the pulsed delivery of cryogen spray have been employed to increase the safety profile of commercially available laser devices approved for the treatment of vascular lesions.2, 6
In dermatologic laser therapy, the use of cold air in analgesia can be considered as effective and inexpensive as current treatment alternatives. Raulin and colleagues7 showed that 86 to 97% of patients preferred the cold air analgesia. The analgesic effect was 37% better than cooling with ice gel. The authors also showed that due to the increased thermal protection of the epidermis, they were able to use higher energy levels and reduce the rate of erythema, purpura, and crusting. Similarly, Greve and associates8 showed that purpura, erythema, edema, and pigmentation were much less marked in the air-cooled areas. In their report, 69% of patients felt that the laser impulses accompanied by cold air were significantly less painful. The authors conclude that cold air is a safe, effective, economical, and environmentally friendly alternative to a cryogen spray cooling system.
- Published on 1 Jan 2009
- Peer Reviewed