Search Results (22)

Background/Objectives: Myopia progression is strongly associated with axial length (AL) elongation, and orthokeratology (Ortho-K) lens design may influence treatment outcomes. This study has the aim to evaluate the impact of lens customization as optical zone diameter between specific higher-order aberrations (HOA) and axial length (AL) changes in myopic children. Methods: This retrospective study evaluated 66 Caucasian myopic children (mean age, 13.3 ± 1.4 years, 60% male) fitted with Ortho-K lenses with varying back optic zone diameters (BOZD, 4.7–6.0 mm) in a Spanish optometric clinic. Baseline mean spherical equivalent (sphere + 1/2 cylinder) was −2.94 ± 1.24 D and AL = 24.52 ± 0.80 mm. Results: After 12 months, children fitted with smaller BOZDs showed significantly less axial elongation than those with larger BOZDs (0.08 ± 0.12 mm vs. 0.15 ± 0.10 mm, p < 0.001) and smaller plus power ring diameter (PPRD). Differences in AL change were observed between PPRD subgroups (larger and smaller than 4.5 mm). HOA revealed distinct patterns: vertical coma increased significantly only in the PPRD > 4.5 mm group (p = 0.003), horizontal coma increased significantly only in the PPRD < 4.5 mm group (p = 0.004), while total coma increased in both, without intergroup differences. Both PPRD subgroups demonstrated significant increases in spherical aberration (p < 0.001). Conclusions: These findings suggest that reducing BOZD, and consequently PPRD, can slow AL elongation more effectively than standard designs, although optical side effects require consideration. Further studies should clarify the interplay of BOZD, PPRD, and pupil size in myopia control. Full article

Using micro-structure components in spectacle lenses has enabled myopia progression control in children and teenagers. However, the optical design of these spectacle lenses has never been discussed, leading to a lack of correct understanding of the underlying optical treatment principles. In this work, array-patterned hexagonal lenslets with two powers of opposite signs were proposed to construct a lenslet array-integrated (LARI) spectacle lens developed for an ongoing, randomized, controlled clinical trial and to support the optical approach to myopia control leveraging retinal image blur. We found that the phase modulation induced by the micro-structures of the lenslet array contributes to the increase in RMS wavefront aberrations, leading to image blur, further inspiring the novel array-patterned micro-structure design with high-order phase elements (HOPEs). The optical performance of both LARI and HOPE spectacle lenses was investigated by simulation and experiment. Full article

Power distribution of progressive power lenses provides usable regions based on power distribution analysis. However, recent studies demonstrated that these regions are not always used for certain tasks as predicted. This work determines the concordance between the actual region of lens use and compares it with the theoretically located regions. The pupil position of 26 subjects was recorded using an eye-tracking system (Tobii-Pro-Glasses 3) at distance and near-reading tasks while wearing a general use progressive power lens. Subjects were asked to read aloud a text showed on a screen placed at 5.25 m and 37 cm while looking though the central and lateral regions of the lens. The pupil position was projected onto the back surface of the lens to obtain the actual region of use for each fixation. Results showed that the actual region of use matched with the theoretically located. On average, the concordance between the actual and theoretical regions of use was 85% for a distance-reading task and 73% for a near-reading task. In conclusion, the proposed method effectively located the actual regions of the lens used, revealing how users’ posture affects lens usage. This insight enables the design of more customized progressive lenses based on the areas used during vision-based tasks. Full article

Cataract disease is strongly associated with progressively accumulating oxidative damage to the extremely long-lived crystallin proteins of the lens. Cysteine oxidation affects crystallin folding, interactions, and light-scattering aggregation especially strongly due to the formation of disulfide bridges. Minimizing crystallin aggregation is crucial for lifelong lens transparency, so one might expect the ubiquitous lens crystallin superfamilies (α and βγ) to contain little cysteine. Yet, the Cys content of γ-crystallins is well above the average for human proteins. We review literature relevant to this longstanding puzzle and take advantage of expanding genomic databases and improved machine learning tools for protein structure prediction to investigate it further. We observe remarkably low Cys conservation in the βγ-crystallin superfamily; however, in γ-crystallin, the spatial positioning of Cys residues is clearly fine-tuned by evolution. We propose that the requirements of long-term lens transparency and high lens optical power impose competing evolutionary pressures on lens βγ-crystallins, leading to distinct adaptations: high Cys content in γ-crystallins but low in βB-crystallins. Aquatic species need more powerful lenses than terrestrial ones, which explains the high methionine content of many fish γ- (and even β-) crystallins. Finally, we discuss synergies between sulfur-containing and aromatic residues in crystallins and suggest future experimental directions. Full article

OBJECTIVE: To evaluate the effect of the orthokeratology (OK) lens design, used in the Montreal Experience cohort, on corneal treatment zone characteristics and their relationship to the pupil. METHODS: This retrospective study follows previously published work and refers to the analysis of 4 different OK lenses. Tangential topography maps were obtained at baseline and after 1 month of OK lens wear. The extracted parameters are: distance treatment zone diameter (DTZD (mm)); relative peripheral power (RPP (D)); mid-peripheral width (MPW (mm)); a new concept, the plus power ratio (PPR (%)), corresponding to the coverage of the pupil area by the positive power zones. RESULTS: DTZD and MPW were significantly different between the lens designs (Welch’s ANOVA). (DTZD (OK 1: 3.68 ± 0.46 mm; OK 2: 3.06 ± 0.67; OK 3: 2.83 ± 0.54; OK 4: 3.20 ± 0.53) MPW (OK 1: 1.65 ± 0.21 mm; OK 2: 1.31 ± 0.40 mm; OK 3: 1.46 ± 0.17 mm; OK 4: 1.57 ± 0.17 mm)). PPR was significantly lower in OK 1 (40.1 ± 22.1%) than the other designs (OK 2: 53.8 ± 18.4%; OK 3: 60.3 ± 13.6; OK 4: 54.7 ± 15.3). CONCLUSION: This study shows that the corneal response to OK lens wear varies with lens design. When analyzed, topographic analysis shows that OK 1 is associated with a larger DTZD, which produces a lower PPR. This may explain why previously published results showed significantly faster axial length (AL) progression with this lens. Full article

This review covers the recent achievements in high-power rare earth (RE)-doped fiber lasers, Raman fiber lasers, and Brillouin fiber lasers. RE-doped fiber lasers have many applications such as laser cutting, laser welding, laser cleaning, and laser precision processing. They operate in several wavelength ranges including 1050–1120 nm (ytterbium-doped fiber lasers), 1530–1590 nm (erbium- and erbium–ytterbium-doped fiber lasers), and 1900–2100 nm (thulium- and holmium-doped fiber lasers). White spaces in the wavelength spectrum, where no RE-doped fiber lasers are available, can be covered by Raman lasers. The heat power generated inside the laser active medium due to the quantum defect degrades the performance of the laser causing, for example, transverse-mode instability and thermal lensing. It can even cause catastrophic fiber damage. Different approaches permitting the mitigation of the heat generation process are considered in this review. Brillouin fiber lasers, especially multiwavelength Brillouin fiber lasers, have several important applications including optical communication, microwave generation, and temperature sensing. Recent progress in Brillouin fiber lasers is considered in this review. Full article

Concentration of solar energy may be obtained by reflection, refraction, or a combination of the two. The collectors of a reflection system are designed to concentrate the sun’s rays onto a photovoltaic cell or steam tube. Refractive lenses concentrate light by having it travel through the lens. The sun’s rays are partially reflected and then refracted via a hybrid technique. Hybrid focus techniques have the potential to maximize power output. Fresnel lenses are an efficient tool for concentrating solar energy, which may then be used in a variety of applications. Development of both imaging and non-imaging devices is occurring at this time. Larger acceptance angles, better concentration ratios with less volume and shorter focal length, greater optical efficiency, etc., are only some of the advantages of non-imaging systems over imaging ones. This study encompasses numerical, experimental, and numerical and experimental studies on the use of Fresnel lenses in various solar energy systems to present a comprehensive picture of current scientific achievements in this field. The framework, design criteria, progress, and difficulties are all dissected in detail. Accordingly, some recommendations for further studies are suggested. Full article

The precision needed in optometric measurements for the correct customization of progressive lenses usually falls short of what is required for accurate prescriptions. This usually stems from the fact that most measurements are obtained using outdated methods, employing either rulers or protractors. While there is equipment available for precise measurements, the cost of purchase and ownership is usually prohibitive. In this context, due to constant progress in high-resolution cameras along with the processing power of handheld devices, another solution has presented itself in different iterations in the past decade, as put forward by different manufacturers of optical lenses. Such a system comprises a mobile computing device with image capture and processing capabilities (tablet or smartphone), along with a marker support system to be mounted on the user’s glasses frames. Aside from cost, the ease of implementation and usage, the advantage of such a system is that the parameters, as measured, allow for better customization, since the eyewear is already in the position in which it will be used. It allows the optometrist to measure parameters such as interpupillary distance, pantoscopic angle and the curvature of the eyewear in relation to the user’s own specific shape and size. This paper proposes a model of a marker support system that is easy to use, precise, low in cost and has minimal impact on the measurements obtained by the optometrist. As such, this paper examines the steps for determining the shape needed for supports in relation to the measurements that need to be taken; a finite element analysis of the support was proposed, along with various tests and modifications that were made to the device until a specific shape and material combination was found that satisfied all of the parameters required. An experimental model of the system was produced and tested on a wide variety of glasses frames with good results, as presented in the following work. Full article

The glacial and torrential basin of Taconnaz (Mont-Blanc massif, France) dominates the Chamonix valley. It is one of the major paths for snow avalanches in the Alps, often triggered by serac falls from the Taconnaz glacier. On 24 November 2018, the basin’s multi-risk nature was further accentuated by a new type of hazard with a rockfall triggered at c. 2700 m a.s.l. It travelled down over a distance of 1.85 km and stopped 165 m away from the construction site of a micro-hydroelectric power station. We studied the triggering conditions at the permafrost lower limit, the effects of the supra-glacial path on the flow patterns, and the fate of the scar and the deposit on torrential activity. By comparing a pre-event Structure from Motion model with a post-event LiDAR model, we estimated the volume of the scar to be 42,900 m³ (±5%). A numerical model was employed to simulate the rapid runout. It revealed the complexity of the flow, attributed to the sequestration of a part of the deposit in crevasses, the incorporation of a significant volume of ice resulting in a transition from a dry granular flow to a mud-like flow, and the presence of numerous deposit zones. Subsequent monitoring of the area after the event allowed for the documentation of the scar’s evolution, including a landslide, as well as the progressive degradation and evacuation of the deposit by the torrent without producing debris flow. The study of the triggering factors indicated glacial retreat as the probable main cause, assisted by the melting of ice lenses left by the permafrost disappearance. Finally, we present replicable methods for managing risks at the site following the event. This event improves the understanding of cascading processes that increasingly impact Alpine areas in the context of climate change. Full article

The management of cataracts in keratoconus patients poses a challenge due to the irregular corneal shape and variability in corneal topography, which may lead to errors in determining corneal power. In this report, we present a case of a 48-year-old male with a history of keratoconus and prior Visian Implantable Collamer lenses and Corneal Allogenic Intrastromal Ring Segments procedures, who presented with a nuclear cataract in his right eye. To address this patient’s complex case, he underwent ICL explantation, cataract extraction, and intraocular lens (IOL) implantation, utilizing the Johnson & Johnson Sensar AR40 monofocal 3-piece lens with a power of −9.5. The Barrett True K formula predicted a spherical equivalent of −1.76, and at the post-operative one-month follow-up, the uncorrected distance visual acuity (UDVA) was 20/60, with pinhole improvement to 20/50. The manifest refraction was −2.50–3.25 × 145, and the best corrected visual acuity was 20/25. This case report highlights the unique challenges encountered in managing keratoconus patients with a history of prior ICL and CAIRS procedures, followed by cataract extraction. Our findings underscore the importance of a comprehensive approach in the management of progressive keratoconus and cataracts to ensure optimal outcomes. Full article

Due to the lack of sensitivity of visual acuity (VA) measurement to quantify differences in visual performance between progressive power lenses (PPLs), in this study, we propose and evaluate an eye-tracking-based method to assess visual performance when wearing PPLs. A wearable eye-tracker system (Tobii-Pro Glasses 3) recorded the pupil position of 27 PPL users at near and distance vision during a VA test while wearing three PPL designs: a PPL for general use (PPL-Balance), a PPL optimized for near vision (PPL-Near), and a PPL optimized for distance vision (PPL-Distance). The participants were asked to recognize eye charts at both near and distance vision using centered and oblique gaze directions with each PPL design. The results showed no statistically significant differences between PPLs for VA. However, significant differences in eye-tracking parameters were observed between PPLs. Furthermore, PPL-Distance had a lower test duration, complete fixation time, and number of fixations at distance evaluation. PPL-Near has a lower test duration, complete fixation time, and number of fixations for near vision. In conclusion, the quality of vision with PPLs can be better characterized by incorporating eye movement parameters than the traditional evaluation method. Full article

This study aimed to evaluate the peripheral defocus induced with a novel perifocal ophthalmic lens for myopia progression control and the potential impact on visual function. This experimental, non-dispensing crossover study evaluated 17 myopic young adults. The peripheral refraction was measured using an open-field autorefractor, at 2.50 m from the target point, in two eccentric points, 25° temporal, 25° nasal, and central vision. Visual contrast sensitivity (VCS) was measured at 3.00 m with a Vistech system VCTS 6500 in low light conditions. Light disturbance (LD) was assessed with a light distortion analyzer 2.00 m away from the device. Peripheral refraction, VCS, and LD were assessed with a monofocal lens and perifocal lens (with an add power of +2.50 D on the temporal side of the lens, and +2.00 D on the nasal side). The results showed that the perifocal lenses induced an average myopic defocus of −0.42 ± 0.38 D (p-value < 0.001) in the nasal retina, at 25° The changes induced by the lower add power in the nasal part of the lens did not induce statistically significant changes in the refraction of the temporal retina. The VCS and LD showed no significant differences between the monofocal and perifocal lenses. Full article

Magneto-optical materials are the fundamental component of Faraday isolators; therefore, they are significantly important for solid-state laser systems. Fluoride magneto-optical crystals such as CeF₃, KTb₃F₁₀ and LiTbF₄ exhibit advantages of wide transmittance range, high optical homogeneity, smaller thermal lensing and weaker thermal induced depolarization effect, and thus are promising candidates for Faraday isolators in high-power solid-state lasers. Recent progress in crystal growth and characterizations of these fluoride magneto-optical crystals are introduced. Possible applications of Faraday isolators based on various fluoride crystals are discussed, especially for solid-state lasers in the ultraviolet (UV) or infrared (IR) spectral region. Full article

As an evolutionary success in life science, wearable biosensor systems, which can monitor human health information and quantify vital signs in real time, have been actively studied. Research in wearable biosensor systems is mainly focused on the design of sensors with various flexible materials. Among them, 2D materials with excellent mechanical, optical, and electrical properties provide the expected characteristics to address the challenges of developing microminiaturized wearable biosensor systems. This review summarizes the recent research progresses in 2D-materials-based wearable biosensors including e-skin, contact lens sensors, and others. Then, we highlight the challenges of flexible power supply technologies for smart systems. The latest advances in biosensor systems involving wearable wristbands, diabetic patches, and smart contact lenses are also discussed. This review will enable a better understanding of the design principle of 2D biosensors, offering insights into innovative technologies for future biosensor systems toward their practical applications. Full article

The purpose of this study is to determine if there is any correlation between the characteristics of the user’s eye movements (EMs) and the preference of the user when wearing different Progressive power lenses (PPLs) distributions. An eye-tracker system with a sample rate of 120Hz and temporal resolution of 8.3 ms (Tobii-X3-120) was used to register EMs of 38 PPL users when reading in a computer screen with 2 types of PPLs (PPLsoft and PPL-hard). Number of fixations, complete fixation time, fixation duration mean, saccade duration mean, saccade distance mean, and number of regressions were analyzed for 6 different regions of the computer screen. A statistically significant difference was observed between the characteristics of the user’s EMs and the user’s PPL subjective preference (p < 0.05*). Subjects that preferred the PPL-hard presented significantly lower complete fixation time, lower fixation duration mean and lower number of regressions than those subjects indicating a preference for the PPL-soft. Results of this study suggest that eye-tracking systems can be used as PPL design recommendation systems according to the user EMs performance. Full article