Fractional ablative lasers are traditionally considered the "gold standard treatment" for atrophic acne scars. Of these, fractional CO2 lasers have deeper reach than fractional erbium yag lasers. Intense beams of laser ablate or vaporise tiny "pixels" of surface skin and scar tissue like an ultra-fine airbrush, triggering skin renewal and collagen remodelling to resurface scars and rejuvenate skin.
In general, faster and more improvements in sunken scars are expected with these ablative resurfacing lasers, as compared to non-ablative lasers like Q-switched lasers.
However, the most common complaint with these lasers is skin recovery time - typically a sunburn-like sensation immediately after, skin redness and roughness for a few days to a week are expected as the skin renews and regenerates itself. There are also concerns such as possible skin darkening (post-inflammatory hyperpigmentation), especially in our darker Asian skin types, even though advancement in the ablative laser technology has improved this aspect. Acne should ideally be well-controlled as well before ablative scar resurfacing.
All in all, the patient needs to be prepared for the downtime and the investment in time and effort for careful skin care and sun avoidance with every session of ablative laser resurfacing, over a course of treatments recommended for their severity of scars.
The popular non-ablative Q-switched Nd-Yag "laser toning", on the other hand, is a relatively comfortable and simple treatment for patients that do not require much preparation or social downtime (mild transient flushing and mild pinpoint petechiae may occur).
Besides the convenience and relative lower risks in Asian skin, many patients find it helpful to control ongoing acne breakouts as well, while lightening the dark acne marks and promoting better healing of fresh scars (hence reducing the development of new permanent sunken scars).
There have been studies showing that non-ablative q-switched lasers can improve the appearance of atrophic acne scars as well, through collagen remodelling that take place over months after a course of treatment. From past experience, this is more likely to yield results in mild to moderate scars.
Adjunct treatments, such as subcision, Rejuran S and fillers, can be used to enhance the results for some scars without causing prolonged downtime. Other patients may opt to undergo ablative resurfacing on the residual deeper scars whenever they can take a little downtime, after improving their overall skin condition and gaining better acne control with the non-ablative lasers.
Of course, the quality of the actual CO2 or Q-swtiched laser being used is very important, as with the hands deciding the parameters and doing the procedure. Other non-ablative lasers, micro-needle radiofrequency and nitrogen plasma treatments are also now available to fulfil the different needs, lifestyle preferences and expectations of patients.