Nd:YAG/Er:YAG dual laser compared with topical steroid to treat vulvar lichen sclerosus: A randomised controlled trial.

OBJECTIVE: To evaluate the efficacy and safety of a novel non-ablative Nd:YAG/Er:YAG dual laser treatment for vulvar lichen sclerosus (LS) in comparison with the recommended first-line therapy with topical steroid. DESIGN: A randomised investigator-initiated active-controlled trial. SETTING: Single tertiary referral centre. POPULATION: Women with vulvar LS. METHODS: Randomisation (2:1) to Nd:YAG/Er:YAG laser therapy or topical clobetasol proprionate therapy. Four laser treatments at 0, 1, 2 and 4 months or decreasing doses of steroid for 6 months. MAIN OUTCOME MEASURES: The primary outcome was the change in objective validated clinical LS score in the laser arm between baseline and 6 months. Secondary outcomes were laser tolerability/safety, symptom scores and patient satisfaction. RESULTS: Sixty-six women were included, 44 in the laser group and 22 in the steroid group. The total LS score decreased by -2.34 ± 1.20 (95% CI -2.71 to -1.98) in women treated with laser compared with a decrease of -0.95 ± 0.90 (95% CI -1.35 to -0.56) in those receiving steroid applications (p < 0.001). Laser treatment was safe and well tolerated. Subjective severity scores (on visual analogue scale) and vulvovaginal symptoms questionnaire scores improved similarly for the laser and steroid arms without significant differences between the two treatments. Patient satisfaction was higher in the laser arm than in the steroid arm (p = 0.035). CONCLUSIONS: Non-ablative dual Nd:YAG/Er:YAG laser therapy was safe and significantly improved clinical outcome and subjective symptoms at the 6-month follow up. This suggests that laser may be a promising alternative to corticosteroid therapy. However, the authors caution regular follow ups because of the premalignant nature of the disease.

Red light instruments for myopia exceed safety limits.

PURPOSE: Low-level red light (LLRL) therapy has recently emerged as a myopia treatment in children, with several studies reporting significant reduction in axial elongation and myopia progression. The goal of this study was to characterise the output and determine the thermal and photochemical maximum permissible exposure (MPE) of LLRL devices for myopia control. METHODS: Two LLRL devices, a Sky-n1201a and a Future Vision, were examined. Optical power measurements were made using an integrating sphere radiometer through a 7-mm diameter aperture, in accordance with ANSI Z136.1-2014, sections 3.2.3-3.2.4. Retinal spot sizes of the devices were obtained using a model eye and high-resolution beam profiler. Corneal irradiance, retinal irradiance and MPE were calculated for an eye positioned at the oculars of each device. RESULTS: Both devices were confirmed to be Class 1 laser products. Findings showed that the Sky-n1201a delivers laser light as a point source with a 654-nm wavelength, 0.2 mW power (Ø 7 mm aperture, 10-cm distance), 1.17 mW/cm2 corneal irradiance and 7.2 W/cm2 retinal irradiance (Ø 2 mm pupil). The MPE for photochemical damage is 0.55-7.0 s for 2-7 mm pupils and for thermal damage is 0.41-10 s for 4.25-7 mm pupils. Future Vision delivers the laser as an extended source subtending 0.75 × 0.325°. It has a 652-nm wavelength, 0.06 mW power (Ø 7 mm aperture, 10 cm distance), 0.624 mW/cm2 corneal irradiance and 0.08 W/cm2 retinal irradiance (Ø 2 mm pupil). MPE for photochemical damage is 50-625 s for 2-7 mm pupils. DISCUSSION: For both of the LLRL devices evaluated here, 3 min of continuous viewing approached or surpassed the MPE, putting the retina at risk of photochemical and thermal damage. Clinicians should be cautious with the use of LLRL therapy for myopia in children until safety standards can be confirmed.

Thermal eye injuries from dermatologic laser treatments-an experimental study.

In recent years, severe ocular complications after dermatological laser therapies have been reported. One hypothesis is thermal damage due to heating of the metal eye shields. The aim of the present study is to evaluate the safety of ocular metal eye shields during laser therapy of the periocular region. For the experimental study, porcine eyelids were exposed to continuously increasing laser energy and multiple pulses using a number of dermatologic laser systems. Temperature differences of the convex and concave surface of metal eye shields were constantly measured using a thermocouple. Maximum increase of the convex surface of shields was + 8.9 °C (± 0.1 °C) provided by the long-pulsed alexandrite laser (20-25-J/cm2 energy, 15-mm spot size, 20-ms pulse duration, 1 Hz). Present data indicate that metal eye shields provide sufficient thermal protection when clinically used laser parameters are applied. Other safety precautions continue to be essential to protect both the patient and the laser operator. These include the use of nonreflective metal eye shields, precise knowledge of laser physics, and a clear understanding of how they interact with ocular and periocular anatomy.

Laser Safety-What Is the Laser Hazard Distance for an Electro-Optical Imaging System?

Laser safety is an important topic. Everybody working with lasers has to follow the long-established occupational safety rules to prevent people from eye damage by accidental irradiation. These rules comprise, for example, the calculation of the Maximum Permissible Exposure (MPE), as well as the corresponding laser hazard distance, the so-called Nominal Ocular Hazard Distance (NOHD). At exposure levels below the MPE, laser eye dazzling may occur and is described by a quite new concept, leading to definitions such as the Maximum Dazzle Exposure (MDE) and to its corresponding Nominal Ocular Dazzle Distance (NODD). In earlier work, we defined exposure limits for sensors corresponding to those for the human eye: The Maximum Permissible Exposure for a Sensor, MPES, and the Maximum Dazzle Exposure for a Sensor, MDES. In this publication, we report on our continuative work concerning the laser hazard distances arising from these exposure limits. In contrast to the human eye, unexpected results occur for electro-optical imaging systems: For laser irradiances exceeding the exposure limit, MPES, it can happen that the laser hazard zone does not extend directly from the laser source, but only from a specific distance to it. This means that some scenarios are possible where an electro-optical imaging sensor may be in danger of getting damaged within a certain distance to the laser source but is safe from damage when located close to the laser source. This is in contrast to laser eye safety, where it is assumed that the laser hazard zone always extends directly from the laser source. Furthermore, we provide closed-form equations in order to estimate laser hazard distances related to the damaging and dazzling of the electro-optical imaging systems.

Segmentation of laser induced retinal lesions using deep learning (December 2021).

OBJECTIVE: Detection of retinal laser lesions is necessary in both the evaluation of the extent of damage from high power laser sources, and in validating treatments involving the placement of laser lesions. However, such lesions are difficult to detect using Color Fundus cameras alone. Deep learning-based segmentation can remedy this, by highlighting potential lesions in the image. METHODS: A unique database of images collected at the Air Force Research Laboratory over the past 30 years was used to train deep learning models for classifying images with lesions and for subsequent segmentation. We investigate whether transferring weights from models that learned classification would improve performance of the segmentation models. We use Pearson's correlation coefficient between the initial and final training phases to reveal how the networks are transferring features. RESULTS: The segmentation models are able to effectively segment a broad range of lesions and imaging conditions. CONCLUSION: Deep learning-based segmentation of lesions can effectively highlight laser lesions, making this a useful tool for aiding clinicians.

Estimation of Lens Stray Light with Regard to the Incapacitation of Imaging Sensors-Part 2: Validation.

Recently, we developed a simple theoretical model for the estimation of the irradiance distribution at the focal plane of commercial off-the-shelf (COTS) camera lenses in case of laser illumination. The purpose of such a model is to predict the incapacitation of imaging sensors when irradiated by laser light. The model is based on closed-form equations that comprise mainly standard parameters of the laser dazzle scenario and those of the main devices involved (laser source, camera lens and imaging sensor). However, the model also includes three non-standard parameters, which describe the scattering of light within the camera lens. In previous work, we have performed measurements to derive these typically unknown scatter parameters for a collection of camera lenses of the Double-Gauss type. In this publication, we compare calculations based on our theoretical model and the measured scatter parameters with the outcome of stray light simulations performed with the optical design software FRED in order to validate the reliability of our theoretical model and of the derived scatter parameters.

A Contact-Sensitive Probe for Biomedical Optics.

Capacitive proximity sensing is widespread in our everyday life, but no sensor for biomedical optics takes advantage of this technology to monitor the probe attachment to the subject's skin. In particular, when using optical monitoring devices, the capability to quantitatively measure the probe contact can significantly improve data quality and ensure the subject's safety. We present a custom novel optical probe based on a flexible printed circuit board which integrates a capacitive contact sensor, 3D-printed optic fiber holders and an accelerometer sensor. The device can be effectively adopted during continuous monitoring optical measurements to detect contact quality, motion artifacts, probe detachment and ensure optimal signal quality.

Requirements for Automotive LiDAR Systems.

Light detection and ranging (LiDAR) are fundamental sensors that help driving tasks for autonomous driving at various levels. Commercially available systems come in different specialized design schemes and involve plenty of specifications. In the literature, there are insufficient representations of the technical requirements for LiDAR systems in the automotive context, such as range, detection quality, resolving power, field of view, and eye safety. For this reason, the requirements above require to be derived based on ADAS functions. The requirements for various key LiDAR metrics, including detection range, field of view, angular resolution, and laser safety, are analyzed in this paper. LiDAR systems are available with various radiation patterns that significantly impact on detection range. Therefore, the detection range under various radiation patterns is firstly investigated in this paper. Based on ADAS functions, the required detection range and field of view for LiDAR systems are examined, taking into account various travel speeds to avoid collision and the coverage of the entire lane width. Furthermore, the angular resolution limits are obtained utilizing the KITTI dataset and exemplary 3D detection algorithms. Finally, the maximum detection ranges for the different radiation patterns are compared under the consideration of derived requirements and laser safety.

Management and prevention of laser complications in aesthetic medicine: An analysis of the etiological factors.

Growing popularity of laser treatment has understandably resulted in increased incidence of potential complications. The analysis of complications, taking into account the causes of their occurrence, is of particular interest. The identification of etiological factors and the development of a step-by-step prophylactic algorithm with their consideration is the way to reduce the number of possible complications in future practice. In this article, we present a classification of the causes of complications associated with various types of laser procedures. This classification was developed on the basis of a review of last 20 years' literature and our own experience in a network of clinics "Linline" in Russia. We identified six groups of the etiological classification of laser complications: errors of patient selection, errors of treatment tactics, wrong choice of device and technology, neglect of treatment protocol, inadequate post-procedural care, individual response of the patient. The causes of all specified groups of complication, except the last one, are preventable causes.

Estimation of Lens Stray Light with Regard to the Incapacitation of Imaging Sensors.

We present our efforts on estimating light scattering characteristics from commercial off-the-shelf (COTS) camera lenses in order to deduce thereof a set of generic scattering parameters valid for a specific lens class (double Gauss lenses). In previous investigations, we developed a simplified theoretical light scattering model to estimate the irradiance distribution in the focal plane of a camera lens. This theoretical model is based on a 3-parameter bidirectional scattering distribution function (BSDF), which describes light scattering from rough surfaces of the optical elements. Ordinarily, the three scatter parameters of the BSDF are not known for COTS camera lenses, which makes it necessary to assess them by own experiments. Besides the experimental setup and the measurement process, we present in detail the subsequent data exploitation. From measurements on seven COTS camera lenses, we deduced a generic set of scatter parameters. For a deeper analysis, the results of our measurements have also been compared with the output of an optical engineering software. Together with our theoretical model, now stray light calculations can be accomplished even then, when specific scatter parameters are not available from elsewhere. In addition, the light scattering analyses also allow considering the glare vulnerability of optical systems in terms of laser safety.

Adherence to optical safety guidelines for laser-assisted hair removal.

BACKGROUND: In recent years, there was a rise in ocular injuries secondary to cosmetic laser-assisted hair removal. PURPOSE: To assess the level of adherence to optical safety guidelines during laser-assisted hair removal performed by nurses or physicians in private practice. METHODS: A cross-sectional study was conducted at thirty-one private laser-assisted hair removal clinics. An electronic random number generator using a cluster random sampling technique was used to select the clinics. The Alexlazr™ (Candela Corp.) device operator's manual checklist was modified to collect data from laser device operators and patients by surveying the laser rooms, interviewing the patients, and observing the treatments. RESULTS: Ninety-four patients treated by different service providers were included from 31 private centers. All treatment sessions were delivered by trained nurses. Only 9.5% had acceptable adherence to optical safety guidelines during hair removal treatment, while the majority (90.5%) of service providers were poorly adherent. None of the providers achieved excellent adherence to optical safety guidelines. The item with the least adherence was the lack of non-reflective floors inside laser rooms in 72.3% of centers. All service providers were familiar with the laser system controls and emergency shutdown (100% adherence). CONCLUSION: There is a significant deficiency in the safety precautions at laser-assisted hair removal centers that can result in devastating ophthalmic injuries. Companies providing laser-assisted hair removal machines should be involved in aiding these centers to implement safety procedures.

Laser Safety Calculations for Imaging Sensors.

This publication presents an approach to adapt the well-known classical eye-related concept of laser safety calculations on camera sensors as general as possible. The difficulty in this approach is that sensors, in contrast to the human eye, consist of a variety of combinations of optics and detectors. Laser safety calculations related to the human eye target terms like Maximum Permissible Exposure (MPE) and Nominal Ocular Hazard Distance (NOHD). The MPE describes the maximum allowed level of irradiation at the cornea of the eye to keep the eye safe from damage. The hazard distance corresponding to the MPE is called NOHD. Recently, a laser safety framework regarding the case of human eye dazzling was suggested. For laser eye dazzle, the quantities Maximum Dazzle Exposure (MDE) and the corresponding hazard distance Nominal Ocular Dazzle Distance (NODD) were introduced. Here, an approach is presented to extend laser safety calculations to camera sensors in an analogous way. The main objective thereby was to establish closed-form equations that are as simple as possible to allow also non-expert users to perform such calculations. This is the first time that such investigations have been carried out for this purpose.

Femtosecond Laser Eyewear Protection: Measurements and Precautions for Amplified High Power Applications.

Ultrafast lasers have become increasingly important as research tools in laboratories and commercial enterprises suggesting laser safety, personal protection and awareness become ever more important. Laser safety eyewear are typically rated by their optical densities (OD) over various spectral ranges, but these measurements are usually made using low power, large beam size, and continuous beam conditions. These measurement scenarios are vastly different than the high power, small beam size, and pulsed laser beam conditions where ultrafast lasers have extremely high peak powers and broad spectra due to the short pulse durations. Many solid-state lasers are also tunable over a broad wavelength range, further complicating the selection of adequate laser safety eyewear. Eighteen laser eyewear filter samples were tested under real-world conditions using a Ti:Sapphire regenerative amplifier with output pulses centered at 800 nm running from 2 Hz to 1 KHz repetition rate. The typical maximum peak laser irrandiance employed was ca. 3 TW/cm2 (800 nm wavelength, 450 uJ/pulse with 80 fs FWHM pulse duration) or less when damage occurred, depending on the sample. While many samples maintained their integrity under these test conditions, many plastic samples showed signs of failure which reduced their OD, in some cases transmitting 4 to 5 orders of magnitude higher than expected. In general, glass filters performed significantly better than plastic filters, exhibiting less physical damage to the substrate and less absorber degradation.

CO2 laser stapedotomy safety: influence of laser energy and time on bone-conduction hearing levels.

Total laser energy in CO2 stapedotomy depends on the laser settings and the amount of applications. It is unclear if the amount of total laser energy affects bone-conduction hearing thresholds and if possible effects are temporary or permanent. Alterations of bone-conduction hearing thresholds after single or multiple-shot CO2 laser stapedotomy were analyzed between 1 and 3 weeks and 1.5-6 months after primary (n = 501) or revision surgeries (n = 153) and correlated to time, laser energy, frequency, surgical technique, and pathology encountered in revision stapedotomy. In both time periods, most patients showed a lower bone-conduction threshold in the four-tone puretone average (PTA) at frequencies of 0.5, 1, 2, and 3 kHz that further improved over time. Between 1 and 3 weeks, the improvement was significant in subgroups with cumulative energies lower 1 J and successful one-shot technique or in revisions without laser application. The remaining subgroups with higher total energies showed significant improvements between 1.5 and 6 months. At 4 and 8 kHz, significant improvements were found during 1.5-6 months after primary and revision surgery independent of the used energy. Repeated CO2 laser applications showed no impairment in bone-conduction thresholds and can thus be considered as safe. In most patients, significant, yet unexplained, improvements in bone-conduction hearing thresholds were noticed in a time- and energy-related pattern.

Patient safety in otolaryngology: a descriptive review.

Human evaluation and judgement may include errors that can have disastrous results. Within medicine and healthcare there has been slow progress towards major changes in safety. Healthcare lags behind other specialised industries, such as aviation and nuclear power, where there have been significant improvements in overall safety, especially in reducing risk of errors. Following several high profile cases in the USA during the 1990s, a report titled "To Err Is Human: Building a Safer Health System" was published. The report extrapolated that in the USA approximately 50,000 to 100,000 patients may die each year as a result of medical errors. Traditionally otolaryngology has always been regarded as a "safe specialty". A study in the USA in 2004 inferred that there may be 2600 cases of major morbidity and 165 deaths within the specialty. MEDLINE via PubMed interface was searched for English language articles published between 2000 and 2012. Each combined two or three of the keywords noted earlier. Limitations are related to several generic topics within patient safety in otolaryngology. Other areas covered have been current relevant topics due to recent interest or new advances in technology. There has been a heightened awareness within the healthcare community of patient safety; it has become a major priority. Focus has shifted from apportioning blame to prevention of the errors and implementation of patient safety mechanisms in healthcare delivery. Type of Errors can be divided into errors due to action and errors due to knowledge or planning. In healthcare there are several factors that may influence adverse events and patient safety. Although technology may improve patient safety, it also introduces new sources of error. The ability to work with people allows for the increase in safety netting. Team working has been shown to have a beneficial effect on patient safety. Any field of work involving human decision-making will always have a risk of error. Within Otolaryngology, although patient safety has evolved along similar themes as other surgical specialties; there are several specific high-risk areas. Medical error is a common problem and its human cost is of immense importance. Steps to reduce such errors require the identification of high-risk practice within a complex healthcare system. The commitment to patient safety and quality improvement in medicine depend on personal responsibility and professional accountability.

Femtosecond Laser Eyewear Protection: Measurements and Precautions.

Ultrafast laser systems are becoming more widespread throughout the research and industrial communities yet eye protection for these high power, bright pulsed sources still require scrupulous characterization and testing before use. Femtosecond lasers, with pulses naturally possessing broad-bandwidth and high average power with variable repetition rate, can exhibit spectral side-bands and subtly changing center wavelengths, which may unknowingly affect eyewear safety protection. Pulse spectral characterization and power diagnostics are presented for a 80 MHz, Ti+3:Sapphire, ≈ 800 nm, ≈40 femtosecond oscillator system. Power and spectral transmission for 22 test samples are measured to determine whether they fall within manufacturer specifications.

A contrastive analysis of laser heating between the human and guinea pig cochlea by numerical simulations.

BACKGROUND: The photo-thermal effect has been hypothesised to be one of the most possible biophysical mechanisms for laser-cochlea stimulation. However, there is a lack of studies to date for direct assessing laser heating in humans due to the large body of evidence required to demonstrate safety and efficacy. Instead, the majority focus on animals like the guinea pig, from which a number of valuable results have been gained. However, in light of the increasing need to improve laser safety, it has became necessary to find out whether studies on animals can shed light on safe laser parameters in the human cochlea. Hence, we conducted this contrastive analysis of laser heating between the human and guinea pig cochlea with the aim of assisting further investigations in this field. METHODS: In this work, a 3D symmetrical model was adopted to simplify the spiraled cochlea. With attention focused on the effect of heat conduction, the time-dependent heat equation was solved using finite element method with the COMSOL Script. In the simulations, cochleae with different sizes and various boundary thermal conditions were utilized. RESULTS: Laser heating in both cochleae has a similar trend. In the first stage, or at the beginning of the laser heating, both cochleae increased their temperatures rapidly. In the second stage in which the laser heating reached a quasi-steady stage, the peak temperatures began to rise slowly as more laser pulses were applied. However, three differences of the laser heating were observed. The first is regarding the temperature rise. The results show that laser heating in guinea pig is higher than that in human under the same laser parameters. The second difference is the fluctuation of temperature rise at the center of the modiolus. There is a larger fluctuation of temperature rise in the guinea pig cochlea, compared with that in the human cochlea. The third one is the time for reaching a steady thermal state. The results show that the guinea pig cochlea takes longer time to reach a steady thermal state than the human cochlea. Those differences are mainly attributed to the distinctive thermal boundaries and the various sizes of the two cochleae. CONCLUSIONS: This study finds that the laser heating in the guinea pig cochlea is higher than that in the human cochlea under the condition of the same laser parameters. However, laser stimulation still displays a high spatial selectivity in both cochleae despite the effects of heat conduction. The results indicate that experimental studies on the guinea pig could appropriately be an alternative model for the sake of laser safety.

Strategies for CO2 Laser Use in Laryngeal Microsurgery: A Systematic Review.

OBJECTIVE: We aim to systematically review the literature addressing perioperative practices for optimal use of the CO2 laser in laryngeal transoral laser microsurgery (TOLMS), with a focus on safety. DATA SOURCES: A systematic review of publications indexed in Medline, Embase, and EBM reviews-Cochrane Central Register of Controlled Trials which evaluated perioperative strategies for the use of CO2 laser in laryngeal TOLMS was conducted. REVIEW METHODS: Records obtained from the search strategy were assessed for eligibility in a 2-step process by 2 independent researchers using the Covidence software. RESULTS: Among 2143 identified records, 103 were included in this study. The majority of studies (n = 25) focused on the use of the CO2 laser in oncologic resection, while 20 addressed the treatment of vocal cord paralysis, 16 discussed the treatment of pediatric or congenital pathologies, 11 detailed the management of benign lesions, and 31 studies tackled other surgical indications. Strategies for safe CO2 TOLMS were highly heterogeneous across studies and included preoperative measures (ie, related to the environment, staff preparation, patient protection, and ventilation), intraoperative precautions (ie, protection of nontarget structures, technical considerations, topical and systemic medications), and postoperative strategies (ie, related to airway protection, oral intake, vocal rest, hospitalization duration, drug regimen, and consultant follow-up). CONCLUSION: The results provided in this study can be used as a framework to guide the creation of laser safety protocols across institutions, guide quality improvement initiatives, the development of simulation training activities, and as a tool to facilitate resident teaching and skill assessment.

Cost-effective, open-source light shutters with Arduino control.

In optical experiments, shutters are devices that open or close a path of light. They are often used to limit the duration of light exposure onto a target or onto a detector to reduce possible light-induced damage. Many commercial shutters are available for different applications - some provide very fast opening and closing times, some can handle large optical powers, and others allow for fail-safe operation. Many of these devices are costly and offer limited control options. Here we provide an open-source design for a low-cost, general purpose shutter system based on ubiquitous actuators (servo motors or solenoids) that are connected to an Arduino-based controller. Several shutters can be controlled by one controller, further reducing system cost. The state of the shutters can be controlled via a display built into the controller, by serial commands via USB, or by electrical control lines. The use of a microcontroller makes the shutter controller adaptable - only control options that are used need to be included, and the design accommodates a selection of display and actuator options. We provide designs for all required components, including 3D print files for the actuator holders and cases, the Arduino code, libraries for serial communication (C and python), and example graphical user interfaces for testing.