What is a laser?
LASERs (light amplification by stimulated emission of radiation) are sources of high-intensity monochromatic (single wave length) coherent light that can be used for the treatment of various dermatologic conditions. How they are used depends on the wavelength, pulse characteristics, and fluence (energy output) of the laser being used, and the nature of the condition being treated.
Various kinds of lasers are available; they are differentiated by the medium that produces the laser beam. Each of the different types of lasers has a specific range of utility, depending on its wavelength and penetration.
What is a ruby laser?
A ruby laser is a solid-state laser that uses a synthetic ruby crystal as its laser medium. The active laser medium (laser gain/amplification medium) is a synthetic ruby rod that is energised through optical pumping (typically by a xenon flashtube).
The wavelength of a laser is measured in namometres (nm). Ruby lasers produce pulses of visible light of a deep red colour, at a wavelength of 694.3 nm. Typical ruby laser pulse lengths are of the order of a millisecond.
How does the ruby laser work?
- The Q-switched ruby laser (QSRL) used for dermatological applications works on the principle of selective thermolysis. Q-switching refers to the technique of producing high intensity laser beams in very short pulses.
- The active medium (a ruby crystal) enables high output energy (100–200 MW) at extremely short pulse times (20–80 nanoseconds) at a wavelength of 694 nm.
- The selected wavelength of laser light is absorbed to a high degree by the target structure (called a chromophore) compared to surrounding tissue.
- The pulse duration of laser energy is shorter than the target structure’s thermal relaxation time – this is the time taken for the target to cool by 50% of its peak temperature after irradiation.
- This shorter pulse duration ensures that the impact of thermal energy is limited to the target structure and does not affect the surrounding tissue.
- When ruby laser light hits the skin, it may be reflected, transmitted, or absorbed. Absorbed energy is most responsible for the clinical effect because it is converted to thermal energy (heat) by the intended targets (chromophores) thereby killing the diseased cells.
- The skin chromophores commonly targeted by the ruby laser are haemoglobin, melanin, and tattoo ink, each of which has its own unique absorption spectrum of laser light.
- Complications result when energy intended for the target chromophore is nonselectively diffused and absorbed by surrounding tissues and structures.
What is ruby laser used for?
The following skin disorders may be treated with ruby laser beams.
- Age spots (solar lentigines ), freckles / ephelides, naevus of Ota/Ito, flat congenital melanocytic naevi like nevus spilus (speckled lentiginous naevus) and cafe-au-lait macules.
- Light pulses (694 nm) target melanin (brown pigment) at variable depth on or in the skin.
- Satisfactory clearing of skin lesions can be achieved after around 1–6 ruby laser sessions at fluence levels of 8–10 J/cm2.
- Treatment may be repeated every 8 weeks.
Hair removal in hypertrichosis (excessive body hair)
- In the non-Q-switched mode, the ruby laser (694 nm wavelength, 3 ms pulse duration, energy fluence 46.5 J/cm2) has been tested as a device for epilation (hair extraction) in patients with hypertrichosis.
- Light pulses target the hair follicle causing the hair to fall out and minimising further growth.
- The percentage of hairs removed per session varies by location on the body, with thinner-skinned areas (eg armpits and bikini area) generally responding better than thick-skinned areas (eg back and chin).
- In general, 3 or more treatments are required to achieve permanent hair growth reduction.
- Treatments are repeated every 4 to 8 weeks.
- The laser treatment is generally ineffective for light-coloured (blonde/grey) hair, but effective for treating dark (brown/black) hair in patients of Fitzpatrick types I to III, and perhaps light-coloured type IV skin.
- Extreme caution is recommended in tanned or darker skinned patients, as the laser can also destroy melanin in normal skin, which results in white patches of skin.
- Patients should avoid sun exposure and use a broad-spectrum sunscreens with a Sun Protection Factor (SPF) of 50 or higher following the procedure.
- The responsiveness of the tattoos to Q-switched ruby laser treatment depends largely on the ink or dye used.
- Blue/black tattoos respond well to ruby laser treatment because they strongly absorb the red laser light. The responsiveness of green tattoo inks varies. Yellow and red tattoos usually do not respond well to the ruby laser.
- In at least one study, the Q-switched ruby laser had the highest clearance rate in blue/black tattoos versus the Q-switched Nd:YAG laser (1064 nm, 10–20 nanoseconds, 3.0 mm spot size, 5–10 J/cm2); and Q-switched alexandrite laser (755 nm, 50–100 nanoseconds, 3.0 mm spot size, 6–8 J/cm2).
- Typical settings for Q-switched ruby laser for tattoo removal are wavelength 694 nm, pulse 25–40 nanoseconds, 5.0 mm spot size and fluence 4–10 J/cm2.
- Four to six treatment sessions at 3-week intervals are necessary for the complete removal of amateur tattoos.
- Owing to their greater pigment density, more treatment sessions are usually required for the complete removal of professionally applied (machine pierced) tattoos (around 6–10 sessions).
- Patients with skin types IV–VI, in particular, show a slower response to the ruby laser than fair-skinned patients. This is because the epidermal melanin, located above the tattoo ink, absorbs a significant portion of the laser light.
- Laser treatment involves the selective destruction of ink molecules that are then absorbed by macrophages (immune cells) and eliminated.
Melasma is an acquired pigmentary disorder characterised by brownish hyperpigmented macules that usually appear on the face. The role of ruby laser in melasma treatment is controversial, as studies showing conflicting results. However, at least one study has shown that 6 sessions of low-dose fractional QSRL (694 nm) treatment at 2-week intervals with fluence of 2-3 J/cm2 and pulse duration of 40 nanoseconds is effective in the treatment of patients with melasma.
What does the laser procedure involve?
It is important that the correct diagnosis has been made by the clinician prior to treatment, particularly when pigmented lesions are targeted to avoid mistreatment of skin cancer such as melanoma. The patient should wear eye protection consisting of an opaque covering or goggles throughout the treatment session.
- Treatment consists of placing a hand piece against the surface of the skin and activating the laser. Many patients describe each pulse to feel like the snapping of a rubber band against the skin.
- Topical anaesthetic may be applied to the area but is not usually necessary.
- Skin surface cooling is applied during all hair-removal procedures. Some lasers have built-in cooling devices.
- Immediately following treatment, an ice pack may be applied to soothe the treated area.
- Care should be taken in the first few days following treatment to avoid scrubbing the area, and/or use of abrasive skin cleansers.
- A bandage or patch may help to prevent abrasion of the treated area.
- During the course of treatment patients should protect the area from sun exposure to reduce the risk of postinflammatory hyperpigmentation.
Are there any side effects from ruby laser treatment?
Side effects from ruby laser treatment are usually minor and may include:
- Pain during treatment (reduced by contact cooling and if necessary, topical anaesthetic)
- Redness, swelling and itching immediately after the procedure that may last a few days after treatment.
- Rarely, skin pigment may absorb too much light energy and blistering can occur (laser burn). This recovers without specific treatment.
- Changes in skin pigmentation. Sometimes the pigment cells (melanocytes) can be damaged leaving darker (hyperpigmentation) or paler (hypopigmentation) patches of skin. Generally, cosmetic lasers are less likely to result in these effects in people with lighter rather than darker skin tones.
- Bruising affects up to 10% of patients. It usually fades on its own.
- Bacterial infection.