Lasers in Medical Science

 Photodynamic therapy (PDT) has developed into an important new clinical treatment for cancer during the past 30 years. The method is non-invasive and based on the photochemical activity of a photosensitising agent present in cells and tissues. In so-called ALA-PDT, protoporphyrin IX (Pp IX) is induced from aminolaevulinic acid (ALA) applied topically or systemically. It has been shown that Pp IX is photodegraded by a photo-oxidation process and that its photoproducts have a characteristic absorption band around 670 nm, as observed both in solution and in cells incubated with ALA. In this study, the involvement of oxygen in the photobleaching process was verified by studying the effect of oxygen depletion using the freeze–pump–thaw (FPT) method. A solution of Pp IX in dimethylformamide (DMF) was exposed to light in the wavelength region 600–700 nm (peak centred at 620 (±25) nm) both in the presence and in the absence of oxygen. The bleaching process was observed by absorbance and fluorescence measurements. Photobleaching was observed in the presence of oxygen, as verified by the build-up of a photoproduct absorbing at 670 nm. When the sample was deoxygenated with the FPT method, the photoproduct absorption peak at 670 nm was missing. These results confirm that the formation of photoprotopor-phyrin is a photo-oxidation process and that no photobleaching takes place in the absence of oxygen. When comparing our results to the studies carried out by N2 bubbling, the N2 bubbling seems to be insufficient to remove the oxygen completely from the solution.

The aims of this study are to generate subtraction images of blue-light autofluorescence (BL-AF) and near-infrared autofluorescence (NIR-AF) from normal eyes, eyes with full thickness macular holes, and eyes with irregular foveal contour, and to compare their autofluorescence patterns. This retrospective study included 44 normal eyes of 22 health individuals, 32 eyes with full thickness macular holes of 32 patients, and 36 eyes with irregular foveal contour of 36 patients. BL-AF and NIR-AF were obtained from all patients and used to generate subtraction images using the Image J software. The decreased signal of central patch was recorded. The central foveal thickness (CFT) and outer nucleus layer (ONL) thickness of fovea were measured to calculate the ONL thickness/CFT ratio. The subtraction images showed regularly increased signal in the central macula of all normal eyes. In contrast, decreased signal of central patch was detected in all full thickness macular holes eyes and 26 out of 36 eyes with irregular foveal contour. No significant difference of the ONL thickness/CFT ratio (F = 2.32, P = 0.113) was observed between normal and irregular foveal contour eyes with or without decreased signal of central patch. Both regularly increased signal and decreased signal of central patch were detected in the eyes with irregular foveal contour. Our results suggest that subtraction images are useful for the assessment of certain macular conditions by providing supplementary information to the green-light autofluorescence and BL-AF.

Laser-assisted thinning (LAT) and laser-assisted opening (LAO) are performed as part of human in vitro fertilization (IVF) to increase the implantation rate in patients with a poor prognosis and in cases of repeated implantation failure. However, an insufficient number of studies have directly compared LAT and LAO using the same methods. Therefore, we compared the effects of LAT and LAO on clinical outcomes according to maternal age in patients with repeated implantation failure. This retrospective study was performed in 509 IVF cycles (458 patients). The cycles were divided based on maternal age and the method used (< 38 years LAT, n = 119 vs. LAO, n = 179 and ≥ 38 years LAT, n = 72 vs. LAO, n = 139). Cleavage-stage embryos before transfer were either thinned or opened using a 1.46-μm noncontact diode laser. We compared the implantation rates and pregnancy outcomes of cycles between LAT and LAO according to maternal age. The characteristics of patients did not differ significantly among the groups (p > 0.05), with the exception of mixed factor infertility, which was more common in the LAT group than in the LAO group among patients < 38 years of age (10.1% vs. 2.8%, p = 0.008). The LAT and LAO groups showed similar rates of biochemical pregnancy, clinical pregnancy, ongoing pregnancy, abortion, implantation, singleton pregnancy, and twin pregnancy (p > 0.05). In conclusion, LAT and LAO had similar clinical outcomes. Therefore, we did not find any evidence that LAT is superior to LAO. In fact, the patients ≥ 38 years of age who underwent LAO tended to have a lower abortion rate. Further study is necessary to confirm these results in a larger population.

To evaluate efficacy and safety of picosecond 755 nm alexandrite laser as compared to 1064 nm QS-Nd:YAG laser for melasma treatment in Asians. Twelve patients received 4 sessions of treatments at 1-month interval in a split-face manner. The right side of each patient’s face received 755 nm picosecond laser, and the other side received 1064 nm QS-Nd:YAG laser. Zoom handpiece of 755 nm picosecond laser at fluence of 0.88–1.18 J/cm2 was applied. The treatment protocol used for 1064 nm QS-Nd:YAG laser was 8 mm spot size at fluence of 2.0 J/cm2 initially followed by 6 mm spot size at fluence of 3.5 J/cm2, and finishing with 4 mm spot size at 3.2 J/cm2. For both 755 nm picosecond laser and 1064 nm QS-Nd:YAG laser, the endpoint was mild erythema and swelling without petechiae. Objective evaluation with visual analogue score was conducted by two independent physicians. Subject self-assessment for each patient was conducted as well. Statistical results showed that higher pigmentation clearance rate was achieved at the 755 nm picosecond laser side after the second treatment. At the 3 months follow-up, greater clearance was observed at the 755 nm picosecond laser side compared to the 1064 nm QS-Nd:YAG side. 755 nm alexandrite picosecond laser has been observed to achieve a faster and better clearance rate for melasma compared to 1064 nm QS-Nd:YAG laser. We conclude that the 755 nm picosecond laser could be a safe and effective modality for melasma treatment in Asians.

The published version contains a mistake in Figure 1. Below is the correct figure.

The aim of this study was to compare the efficacy of topical piroxicam and EMLA cream on pain control and subsequent inflammation in neodymium:yttrium–aluminum–garnet (Nd:YAG) 1,064 nm laser hair removal in female volunteers. Fifty female volunteers were enrolled in this prospective, randomized, double-blind, clinical study over a 6-month period. Patients were randomly assigned to receive topical piroxicam as group Piroxicam or EMLA cream as group EMLA. Topical analgesics were applied to the treatment sites for 60 min. The pain scores [on a visual analog scale (VAS)] and side effects were recorded before the hair removal, during the hair removal, at the end of the hair removal, and 1 h, 2 h and 24 h after the hair removal. Patients’ characteristics and the treatment settings of the Nd:YAG 1,064 nm laser were similar in the two groups. The pain scores (VAS) were similar, and satisfaction was high in both groups after the hair removal. The number of blanching and erythema episodes were significantly higher in group E than in group P (P < 0.001). Inflammatory side effects were less frequent in group P than in group E after the procedure (P < 0.001). This study showed that topical piroxicam and EMLA provided adequate and similar pain relief after Nd:YAG 1,064 nm laser hair removal in female volunteers. Topical piroxicam was associated with fewer inflammatory side effects than was EMLA cream, because of its anti-inflammatory effect after the procedure.

The present pilot study investigated the analgesic efficacy of light-emitting diode (LED). In view of a standardised and controlled pain reduction study design, this in vivo trial was conducted on experimentally induced delayed-onset muscle soreness (DOMS). Thirty-two eligible human volunteers were randomly assigned to either an experimental (n=16) or placebo group (n=16). Immediately following the induction of muscle soreness, perceived pain was measured by means of a visual analog scale (VAS), followed by a more objective mechanical pain threshold (MPT) measurement and finally an eccentric/concentric isokinetic peak torque (IPT) assessment. The experimental group was treated with infrared LED at one of both arms, the other arm served as control. Irradiation lasted 6 min at a continuous power output of 160 mW, resulting in an energy density of 3.2 J/cm2. The subjects of the placebo group received sham irradiation at both sides. In post-treatment, a second daily assessment of MPT and VAS took place. The treatment and assessment procedure (MPT, VAS and IPT) was performed during 4 consecutive days. Statistical analysis (a general linear model followed by post hoc least significant difference) revealed no apparent significant analgesic effects of LED at the above-described light parameters and treatment procedure for none of the three outcome measures. However, as the means of all VAS and MPT variables disclose a general analgesic effect of LED irradiation in favour of the experimental group, precaution should be taken in view of any clinical decision on LED. Future research should therefore focus on the investigation of the mechanisms of LED action and on the exploration of the analgesic effects of LED in a larger randomised clinical trial and eventually in more clinical settings.

The aim of this in-vitro study was to evaluate positive effects of the carbon dioxide laser (CO2, 10,600 nm) with acidulated phosphate fluoride (APF) gel on enamel acid resistance. Twenty extracted human third molars (40 surfaces) were randomly assigned into four groups: group C, untreated control; group L, CO2 laser alone group; group F, APF 1.23% fluoride gel; and group FL, APF 1.23% gel and laser. Samples from group L were irradiated with a CO2 laser for 30s. The parameter settings used were average power, 0.73 W; time on, 100 μs; time off, 40 ms; tip-to-tissue distance, 20 mm; tip diameter 700 μm; and energy density with movements, 5 J/cm2. Samples from group F were treated with the APF gel for 4 min, and the gel was washed off with distilled water. The enamel samples from group FL were treated with APF gel for 4 min and then irradiated with the CO2 laser for 30s without removing the gel. Each enamel sample was placed in 50 ml soft drink (pH = 2.75) for 10 min then rinsed with deionized water and stored in artificial saliva at 37 °C for 1 h. Samples were assessed for Vickers hardness number (VHN) before and after treatments and subjected to SEM analysis. Data were analyzed using a one-way analysis of variance (ANOVA) and Tukey’s test (α < 0.05). After the acid challenge, the untreated C group was demineralized to a great extent and the enamel surface was with the lowest mean score of microhardness. The observed VHN in the control (C group) had a mean value of 176.13, the scores in the CO2 laser group (L group) were with mean value of 238.40, the F group with a mean value of 218.45, and the fluoride-treated and laser-irradiated FL group—with a mean of 268.28 VHN. Paired t test performed to compare groups C, L, F, and FL has shown that group FL has greater resistance to decrease in microhardness of dental enamel (P ≤ 0.05) on exposure to acidic protocol. After the acid challenge, the fluoride-treated and laser-irradiated samples (group FL) showed the least diminution in enamel surface microhardness. The sub-ablative carbon dioxide laser irradiation in combination with fluoride treatment is more effective in protecting enamel surface and resisting demineralization than CO2 laser irradiation or fluoride alone.