Initial clinical experience with the picosecond Nd:YLF laser for intraocular therapeutic applications

AIMS/BACKGROUND—Compared with nanosecond (ns) pulses of conventional Nd-YAG lasers, picosecond (ps) laser pulses allow intraocular surgery at considerably lower pulse energy. The authors report initial clinical experiences using a Nd:YLF ps laser for the treatment of various indications for photodisruption.
METHODS—A Nd:YLF laser system (ISL 2001, wavelength 1053 nm) was used to apply pulse series of 100-400 µJ single pulse energy at a repetition rate of 0.12-1.0 kHz. Computer controlled patterns were used to perform iridectomies (n=53), capsulotomies (n=9), synechiolysis (n=3), and pupilloplasties (n=2). Other procedures were vitreoretinal strand incision (n=2) and peripheral retinotomy (n=1). For comparison, 10 capsulotomies and 20 iridotomies were performed with a Nd:YAG ns laser. The ps laser cut of an anterior capsule was assessed by scanning electron microscopy (SEM).
RESULTS—Open, well defined iridectomies (mean total energy 4028 mJ, mean diameter 724 µm) were achieved at first attempt in 92% of the cases. In 64% an iris bleeding and in 21% an IOP increase of >10 mm Hg occurred. All capsulotomies were performed successfully (mean energy 690 mJ/mm cutting length) but with a high incidence of intraocular lens damage. The attempted vitreoretinal applications remained unsuccessful as a result of optical aberrations of the eye and contact lens. Although ps laser capsulotomies and iridectomies required much higher total energy than ns procedures, the resulting tissue effects of the ps pulses were more clearly defined. SEM examination of a ps incision of the anterior lens capsule demonstrated, nevertheless, that the cut was more irregular than the edge of a continuous curvilinear capsulorhexis.
CONCLUSION—Series of ps pulses applied in computer controlled patterns can be used effectively for laser surgery in the anterior segment and are considerably less disruptive than ns pulses. The ps laser is well suited for laser iridectomies while the ns laser is preferable for posterior capsulotomies. As vitreoretinal applications remained unsuccessful, the range of indications for intraocular photodisruption could not be extended by the ps laser.

Keywords: picosecond laser; intraocular photodisruption; capsulotomy; iridotomy; iridectomy     

Treatment of pigmentary disorders using picosecond laser in Asian patients: A meta‐analysis and systematic review

There were many studies evaluating the effect of picosecond (PS) lasers, but no meta‐analysis examined the effects of PS laser in the treatment of pigmentary disorders in Asians. The aim of this article was to review the before‐after effect of PS laser in Asians for the treatment of pigmentary disorders. PubMed, Embase, and Cochrane library were searched for articles published up to May 2020. The evaluations were summarized into a 4‐point scale that ranged from <25% (poor), 25%‐50% (fair), 50%‐75% (good), and 75%‐100% (excellent). Effect sizes (ESs) were calculated according to laser wavelengths and lesion types. There were two randomized controlled trials, three single‐arm trials, and three case series, with 200 patients. At 3 months after treatment, of all included patients, 3% (95%CI: 1%‐6%) were evaluated as poor or worse, 9% (95%CI: 2%‐21%) as fair, 29% (95%CI: 12%‐50%) as good, and 56% (95%CI: 28%‐83%) as excellent. The 532 and 1064, and 755 nm PS lasers had similar ESs across all four response groups. This meta‐analysis suggested that 56% of Asian patients who underwent PS laser for the treatment of pigmentary disorders were evaluated as “excellent” about the pigment clearance by a dermatologist at least 3 months after treatment.     

Prospective study of removing solar lentigines in Asians using a novel dual‐wavelength and dual‐pulse width picosecond laser

Objectives

Quality‐switched (QS) lasers are known to be an effective treatment for removing solar lentigines, however, high incidence of post‐inflammatory hyperpigmentation (PIH) is a concern in darker skin types. The objective of this study was to evaluate the efficacy and safety of a dual‐wavelength and dual‐pulse width picosecond Nd:YAG laser for removing solar lentigines in Asians.

Methods

This was a prospective, IRB‐approved study. Twenty cases with solar lentigines on the face were enrolled for treatment and evaluated at 1‐ and 3‐month after the final treatment. Results were assessed by blinded evaluators using a 5‐grade percentage improvement scale and Melanin index (MI) measured by a reflectance spectrophotometer. A patient self‐assessment questionnaire was also administered using a 5‐grade improvement scale. Additional treatment was performed if the improvement was less than 75% or the lentigo partially remained after 4 weeks. Histological evaluation was performed to compare the differences between the current picosecond laser and a QS Nd:YAG laser 532‐nm using light and electron microscopy.

Results

Forty‐three lesions in 20 females, skin type III or IV, age 53.7 ± 9.75 were treated and evaluated. The laser setting was: 532‐nm, 750 picoseconds, average fluence of 0.35 ± 0.06 J/cm [2] using a spot size of 3 or 4 mm. Forty lesions (93.02%) achieved over 75% clearance with a single treatment and the other three lesions (6.98%) needed two treatments. PIH occurred only in 4.65% of lesions. The average score of the blinded evaluators’ assessment was 4.77 and 4.58 on a 5‐grade percentage improvement scale. The patients’ self‐assessment rating was 4.76 and 4.67 on a 5‐grade scale at 1‐ and 3‐month follow‐up, respectively. The improvement rate of relative MI (MI in the lesion minus that of the normal area) was 77.60 ± 36.27% and 76.93 ± 20.95% at 1‐and 3‐month follow‐up. Histology showed vacuolar formation by both lasers in the epidermis that were different sizes between lasers. Electron microscopy showed destruction of melanosomes with surrounding tissue damage with the QS laser and without particular damage with the picosecond laser.

Conclusions

To the best of our knowledge, this is the first study using a picosecond Nd:YAG laser 532‐nm for removing solar lentigines in darker skin types that includes histological evaluation. Although there are many options to treat solar lentigines, our results suggest that picosecond laser with preferable endpoint determination can be a safer and more effective treatment over conventional treatments in Asian patients. Lasers Surg. Med. 50:851–858, 2018. © 2018 Wiley Periodicals, Inc.     

1064-nm Nd:YAG皮秒点阵激光与超脉冲CO2点阵激光治疗面部萎缩性痤疮瘢痕的临床比较

目的 探究1064-nm Nd:YAG皮秒点阵激光与超脉冲CO2点阵激光治疗面部萎缩性痤疮瘢痕的疗 效与安全性。方法 选取2021年6月-2023年6月于我院激光科接受治疗的62例面部萎缩性痤疮瘢痕患者作 为研究对象,按照不同的治疗方法分为皮秒点阵激光组和CO2点阵激光组,各31例。皮秒点阵激光组给予 1064-nm Nd:YAG皮秒点阵激光治疗,CO2点阵激光组给予超脉冲CO2点阵激光治疗,比较两组ECCA权 重评分、疗效自评分、满意度评分及术后不良反应发生情况。结果 两组治疗后ECCA权重评分均较治疗 前降低（P ＜0.05）,且皮秒点阵激光组的ECCA权重评分高于CO2点阵激光组（P ＜0.05）;CO2点阵激光 组疗效自评分高于皮秒点阵激光组（P ＜0.05）;皮秒点阵激光组不良反应发生情况低于CO2点阵激光组 （P ＜0.05）;两组满意度比较,差异无统计学意义（P＞0.05）。结论 1064-nm Nd:YAG皮秒点阵激光与 超脉冲CO2点阵激光均能有效改善面部萎缩性痤疮瘢痕,超脉冲CO2点阵激光疗效更好,而皮秒点阵激光 不良反应发生情况更少。     

Additive Manufacturing of Dense Ti6Al4V Layer via Picosecond Pulse Laser

Ultrashort pulse laser shows good potential for heat control improvement in metal additive manufacturing. The challenge of applying ultrashort pulse laser as the heat source is to form a fully melted and dense microstructure. In this study, a picosecond pulse laser is introduced for fabricating single layer Ti6Al4V samples. The results, by examining through X-ray computed tomography (X-CT), scanning electron microscopy (SEM), show that highly dense Ti6Al4V samples were fabricated with optimized process parameters. The analysis of the cross section presents a three-zones structure from top to bottom in the sequence of the fully melted zone, the partially melted zone, and the heat-affected zone. A semi-quantitative study is performed to estimate the thermal efficiency of melted pool formation. The mechanical properties of the samples are tested using nano-indentation, showing an elastic modulus of 89.74 ± 0.74 GPa. The evidence of dense melted pool with good mechanical properties indicates that the picosecond laser can be integrated as the heat source with the current metal additive manufacturing to fabricate parts with accuracy control for the smaller size of thermal filed.     

Successful and quick treatment of nevus of Ota with 755nm picosecond laser in Chinese

ABSTRACT

Nevus of Ota, also known as nevus fusco-caeruleus ophthalmo-maxillaris, is a benign dermal melanocytosis. In the past, this disease was usually treated by Q-switched laser therapy, but the course of treatment was relatively long. In recent years, it has been reported that 755nm picosecond laser, which was firstly reported to treat tattoos, is also effective in the treatment of nevus of Ota. Here, we report six cases of nevus of Ota which were treated with 755nm picosecond laser in Chinese people. We find amazingly that these lesions almost disappeared after only one or two sessions of treatment.