Introduction to scar removal using lasers

Scars are a permanent mark left on the skin due to wound healing. Most scars are harmless but some scars that cause pruritus, pain, disfigurement or are disabling need to be removed. There are mainly three types of scars, needing removal; hypertrophic and atrophic scars, and keloids.

The advent of lasers has led to improved treatment of scars. Laser treatments commonly used for scar removal for decades include continuous wave CO2, argon, Nd: YAG and Er: YAG lasers. The choice of laser depends on absorption characteristics of the target, type of scar, and histories of the scar, trauma and previous therapy.

Hypertrophic and keloids treatment

CO2, argon and Nd: YAG lasers have been used for a long time to treat these scars. However, the improvements were temporary and recurrences were frequent. The CO2 laser moreover aerosolized hepatitis B and C, and HIV, and other viruses, putting the surgeon at risk. Use of these lasers were therefore, soon discontinued.

Later, the vascular specific 585 nm flash-pumped PDL was found better in treating these scars. Hypertrophic scars, less than a year old, responded better and needed fewer treatments, compared to older scars. Scars in dark skinned patients also showed better responses to treatment. Lower fluences were associated with more rapid response and multiple treatments with greater clinical improvements. However, no fluence dependence was noted.

Many aspects of the scar condition show imrovements with combined therapies. PDL combined with intralesional corticosteoids showed reduced pruritus in one study. Another study found increased pliability, and reduced pruritus and sclerosis with or without steroids, though addition of corticosteroids did show more improvements. PDL with CO2 lasers, showed better results in nonerythemous and minimally hypertrophic scars.

Atrophic scars are more difficult to treat. Traditional methods used various means to mask the scars but the side effects limited their use. Today, lasers offer a better alternative. Resurfacing may be done by ablative or non-ablative laser systems.

Ablative resurfacing of atrophic scars

Atrophic scars are treated by CO2 and Er: YAG lasers.

CO2 laser: The latest laser technology allows a more selective ablation of the water containing tissues, resulting in a more predictable and reproducible tissue vaporization. The new system also softens the transition between the atrophied skin of the scar and the normal skin around it. They may also trigger increased collagen production.

An adverse effect of old CO2 laser treatment was char formation. The development of lasers with high energy densities and ultra-short pulse durations allowed controlled heat delivery and absorption, resulting in char-free ablation. While most adverse effects of the old CO2 lasers have been eliminated by the new system, short-term problems like, transient erythema, pruritis and transient scarring remain. The single pass system, with fewer side effects, may be safer than the multi pass system. One study reported a more natural skin condition with single-pass resurfacing. High fluences did not show more thermal damage than average fluences.

Er: YAG resurfacing: Pulsed Er: YAG lasers, at selected wavelengths are 10 times more selective in targeting the water than CO2 lasers. They are also more penetrating and may cause pinpoint bleeding. However, although overall they cause less thermal damage, the clinical improvement is less. This laser is recommended for treating superficial atrophic scars as they give results similar to CO2 lasers and have reduced healing time.

Combined Er: YAG/ CO2 laser: This combined system can deliver the ablation of the erbium wavelength and the deeper penetration of CO2 laser. Studies show reduced duration of crusting, swelling and itching. This system seems to deliver just enough non-specific energy to stimulate neocollagen production and also vaporize enough tissue. The final word on combined Er: YAG/ CO2 laser system must await more trials.

Non-ablative resurfacing of atrophic scars

This system has lately become fairly popular due to mainly little or no downtime involved. The Nd: YAG was the first laser system developed exclusively for non-ablative skin resurfacing.

It employs light from the visible and mid infrared sections of the spectrum. Non- ablative lasers have been very successful in treating acne scars. There are enough studies to corroborate this. The ability of these lasers to improve skin texture has also been well demonstrated.

The future may see non-ablative laser systems combined with subcutaneous incision, punch excision and fat grafting, in the treatment of acne scars.

Laser treatment for hypertrophic burn scars

These scars are more difficult to treat because of their proliferative nature. Several trials have proved the flash pumped 585nm PDL laser quite effective in reducing pruritis, tenderness and burning, with minimum pain and invasiveness. In future the benefits, if any, of combined therapies or shorter pulse widths in hypertrophic burn scars may be explored.