Biomedical Engineering Reference
In-Depth Information
(
A
)
(
B
)
Figure 9.8
(
A
) Thyroidectomy scar at least 5 years after surgery. (
B
) Signifi cant improvement is seen 6 weeks after a single treatment with Fraxel Re:Pair using
20 mJ and 15% density. Although early treatment is preferable, even older scars such as this may respond extremely well. Only the scar was treated, not the
photodamaged neck.
(
A
)
(
B
)
Figure 9.9
Sharply defi ned ice-pick and small crater scars are visible (
A
) prior to treatment. (
B
) Improvement in scars was achieved in a step-wise fashion using
punch excision followed by AFR over the full cheeks and then NAFR using Fraxel Re:Store 50 mJ, 35% density in multiple sessions confi ned to the visible scars.
in line with that of the blinded evaluators who found mini-
mal change with subcision at 3 and 6 months (108,109) in
20 patients. It would be unusual for subcision to result in sig-
nifi cant improvement as an isolated single treatment as done
in this study. Once of these adjunctive surgical procedures
have been performed, then laser treatment should be more
effective (Fig. 9.9).
In evaluating acne scarring, there are two types of dyspig-
mentation that are particularly bothersome to patients.
Although they are not truly scars, they may persist for as long
as a year or more and should be treated to hasten their resolu-
tion. These two macular dyspigmentations follow infl amma-
tory acne and are postinfl ammatory erythema and PIH
(107-110). PIH generally occurs in patients with Fitzpatrick
skin types III and IV. Topical therapy with retinoids and hydro-
quinone is often effective, but at times it is necessary to treat
with lasers. Generally, spot treatment is done with Q-switched
alexandrite or ruby lasers or IPL. It is best to treat at low
fl uences as too aggressive an approach is likely to result in the
recurrence of PIH. Therefore, two to four sessions are planned
at 2- to 4-week intervals.
When the patient has red macules that are secondary to the
healing phase of infl ammatory acne, there is usually some
active acne as well. The PDL and the IPL have both been used
in managing this condition. The mechanism of action is
thought to be absorption of light energy by porphyrins pro-
duced by
Propionibacterium acnes
, which induces bacterial
death (111).
There are confl icting reports in the literature regarding effi -
cacy. One controlled study of 40 patients treated with one or
two sessions of subpurpuric dosing using 585-nm PDL showed
no benefi t (112). However, a very similar study of 41 patients
by a different group found signifi cant improvement (113).
A study performed in 2006 (114) demonstrated a signifi cant
increase in TGF-
1 messenger RNA levels induced by 585-nm
PDL treatment. This may be signifi cant as far as promoting
β