The technique of Q switching provides the principle of selective photo thermolysis can be applied to the pigmented lesions to achieve the desired clinical results without much damage to the surrounding area. Most pigmentary skin lesions, whether epidermal or dermal, acquired or congenital, can be treated with Q-switched lasers of blue, green, and infrared light. The clinical indications of a Q-switched NdYAG laser are:

Pigmented Lesions

While the epidermal lesions respond best to 532 nm (frequency-doubled NdYAG) the dermal lesions are better treated with 1064 nm. Q-switched lasers are the gold standard for the treatment of tattoos.

Lentigines:

usually, 1-2 sessions are enough to clear lentigines at 532 nm.

Cafe-au lait macules:

these can be treated effectively in 1-2 sessions, but recurrence is common which requires multiple treatments

Freckles

Dermal pigmented lesions: Nevus of Ota, Nevus of Ito, Mongolian spots, Hori’s nevus. Multiple sessions are usually required with the near-total clearing of the lesion in most cases.

Medium depth nonablative skin resurfacing

Frequency-doubled 532 nm Q switched is a well-established technology for treating aging. When used at lower fluences with larger spot size, it is a medium depth laser peel, with less downtime and high patient satisfaction. However, due to the risk of post-inflammatory pigmentary changes in Indian skins, it should be used only after a test patch and adequate sun protection advice to the patient.

Melasma

Lower energy and fewer repetitions are adequate to produce a marked improvement. Improvement will need to be maintained by repeated treatments. However, recurrence is common in melasma.

Tattoos

Q-switched NdYAG 1064 nm, due to its longer wavelength, higher fluence, and shorter pulse, has emerged as a better laser for the black and dark blue/ black tattoo pigment.

Professional tattoos:

Most of such tattoos have an even distribution of ink, mainly in subcutaneous tissue. Ink quality is good; hence, 4-6 treatments are usually required. Amateur tattoos: Usually these are easy to remove, but in some cases, if the ink is a deeper level, a few extra sessions could be required.

Cosmetic tattoos:

Cosmetic tattoos like eyebrows and eye and lip lines are mostly made of iron-based inks. This can sometimes oxidize and turn black, so a test patch must be given.

Laser-assisted Hair Reduction

Though the long-pulsed lasers are gold standards for the removal of terminal hair, Q-switched laser has been tried with and without topical carbon suspension. Q-switched pulses produce a photomechanical impact on the tissue and also on the hair shaft and hair follicle, causing reduction as well as delay in the hair growth cycle. Since it is not color-dependent, it can be suited for all skin types, even on tanned skins without fear of pigmentary changes.

Dark lips

Dark lips are a common cosmetic concern in India. Two to four sessions of Q-switched 532 nm is an effective treatment for lip lightening.