Much of the research relating to the effects of the PDL on scars has been led by Dr Tina Alster in Washington, DC. She noted (Alster et al, 1993) that the PDL was able to alter argon laser-induced scars, which are often erythematous and hypertrophic. By using optical profilometry measurements she demonstrated a trend toward more normal skin texture as well as reduction in observed erythema. This work was extended to the treatment of erythematous and hypertrophic scars (Alster and Williams, 1995) using objective measurements; clinical appearance (colour and height), surface texture, skin pliability and pruritus could all be improved.
It is not known how the PDL improves the appearance of hypertrophic and keloidal scars. Microvascular damage may effect collagen or collagenase activity within the scar. Thermal damage to abnormal collagen within the hypertrophic scar may allow remodelling, and reduction in endothelial cell volume can affect type V collagen, which is increased in hypertrophic scars (Hering et al, 1983). Mast cell alterations after laser irradiation may also be of importance.
Although established hypertrophic scars can respond to treatment, early treatment of scars within the first months might prevent hypertrophy in individuals who are keloid-prone. I have certainly seen the benefits of early PDL treatment of excised recurrent keloids (Smith, Lanigan and Murison, unpublished observations). In a group of 11 patients treated in this way, none had a recurrent keloidal scar. Treatment at 6.5-7.5Jcm2 with a 5mm spot or 6-6.75Jcm2 with a 7mm spot is usually used. Treatment is repeated at 6- to 8- weekly intervals depending on clinical response. Keloidal scars require multiple treatments and the response is unpredictable. There may be additional benefits from using newer PDL with wavelengths of 590 or 595 nm but there is no published work to confirm this.
Alster’s work has been confirmed by Dierickx et al (1995), who treated 15 patients with erythematous/hypertrophic scars and obtained an average improvement of 77% after an average of 1.8 treatments. Goldman and Fitzpatrick (1995) also treated 48 patients with similar laser parameters. Scars less than 1 year old did better than those more than 1 year old and facial scars did better there was an 88% average improvements, with total resolution in 20% after 4.4 treatments. Similar results were also seen in erythematous and hypertrophic facial acne scars by Alster and McMeekin (1996). Combinations of CO2¬ and PDL treatment of hypertrophic non-erythematous scars have also shown additional benefit of the PDL compared to the CO2 laser alone (Alster et al, 1998).
For persistent scars combinations of intralesional corticosteroid injections, steroid impregnated tapes and laser therapy may be necessary (Sawcer et al, 1998).
More recent work by Manuskiatti et al (2001) showed improvement in scarring following treatment with the pulsed dye laser at varying fluences of 3, 5 and 7 Jcm-2. There was a trend for lower fluences to show most improvement and multiple treatments were required.
Two studies have compared the effects of pulsed dye laser treatment with other treatment modalities, particularly intralesional steroids. Alster (2003) compared pulsed dye laser treatment alone with laser therapy combined with intralesional corticosteroid treatment. Both treatment arms produced improvement in scars and there was no significant difference between the two treatments. Manuskiatti and Fitzpatrick (2002) compared scar treatment with intralesional corticosteroids alone or combined with 5-fluorouracil or 5-fluorouracil alone or the pulsed dye laser using fluences of 5 Jcm-2. All treatment areas were improved compared to baseline, there was no significant difference in treatment outcome compared to method of treatment. The highest risk of adverse sequelae occurred in the corticosteroid intralesional group. They concluded that treatment with intralesional corticosteroid alone or in combination with 5-fluorouracil or 5-fluorouracil alone and pulsed dye laser treatment are comparable.
Other studies however, have failed to demonstrate substantial effects of the pulsed dye laser on scars (Allison et al 2003; Paquet 2001; Whittenberg et al 1999;). Paquet assessed laser treated scars using remittance spectroscopy. Although a discrete decrease in redness of the scars was reported clinically this was not confirmed by objective data. Whittenberg et al, in a prospective single blind randomized controlled study compared laser treatment with silicon gel sheeting and controls. Although there was an overall reduction in blood volume and flow and scar pruritis over time, there were no differences detected between the treatment arms and the control groups. Allison et al, treating old and new scars with the pulsed dye laser with fluences of 5 to 6 Jcm-2 were unable to demonstrate any statistical differences between treatment and control by photographic assessments nor surface profile measurements. However, they did notice a significant improvement in scar pruritis in the active group compared with the controlled group.
In conclusion, there are now multiple studies assessing the effects of the pulsed dye laser in the treatment of scars. Although results are conflicting, particularly when controlled studies are performed, it would appear that in some cases laser therapy can be beneficial in the treatment for scars. It is likely that redness and pruritis are the two parameters that are most likely to significantly improve with this treatment.
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