Search Results (694)

In this paper, the problem of assessing the twistability of a given bona fide cross-spectral density is tackled for the class of Schell-model sources, whose shift-invariant degree of coherence is represented by a real and symmetric function, denoted as μ(−r)=μ(r). By employing an abstract operatorial language, the problem of determining the highly degenerate spectrum of a twisted operator W^u is addressed through a modal analysis based on the complete knowledge of the spectrum of the sole twist operator T^u, as found by R. Simon and N. Mukunda. To this end, the evaluation of the complete tensor of the matrix elements ⟨n′,ℓ′|W^u|n,ℓ⟩ is carried out within the framework of the so-called extended Wigner distribution function, a concept recently introduced by M. VanValkenburgh. As a nontrivial application of the algorithm developed here, the analytical determination of the spectrum of saturated twisted astigmatic Gaussian Schell-model sources is also presented. Full article

Background and Objectives: Amblyopia is a condition where children undergo unilateral or bilateral vision loss due to a variety of disorders that impact the visual pathway. The assessment of retinal nerve fiber layer (RNFL) thickness in amblyopia has made optical coherence tomography (OCT) a useful technique for studying the pathophysiology of this condition. This study was conducted to assess OCT results for various forms of amblyopia, including macular thickness and peripapillary RNFL thickness. It is the first of its kind in Jordan. Materials and Methods: Sixty-one individuals, aged 14 to 67, who had been diagnosed with unilateral amblyopia participated in a prospective study. Both eyes underwent spectral-domain OCT imaging, and clinical and demographic information was gathered. Relationships between different types of amblyopia and OCT measurements were investigated. Results: Compared to the contralateral fellow eyes, the amblyopic eyes showed thicker fovea, and there were differences in foveal and macular thickness observed between the sexes. Individuals with anisometropic amblyopia exhibited a greater central macular thickness. While nasal optic nerve thickness was adversely correlated with age, inferior optic nerve thickness was considerably lower in amblyopia. Conclusions: This research indicates unique OCT traits in amblyopic eyes, which may have a role in amblyopia diagnosis and treatment. The prevention of long-term visual impairment depends heavily on early detection and care. More studies using larger cohorts and longitudinal designs are necessary to improve our knowledge of the pathogenesis of amblyopia and to provide the best possible clinical management approaches. Full article

Bulk 2D electronic–vibrational (2D-EV) and 2D vibrational–electronic spectroscopies (2D-VE) were previously developed to correlate the electronic and vibrational degrees of freedom simultaneously, which allow for the study of couplings between electronic and vibrational transitions in photo-chemical systems. Such bulk-dominated methods have been used to extensively study molecular systems, providing unique information such as coherence sensitivity, molecular configurations, enhanced resolution, and correlated states and their dynamics. However, the analogy of interfacial 2D spectroscopy has fallen behind. Our recent work presented interface-specific 2D-EV spectroscopy (i2D-EV). In this work, we develop interface-specific two-dimensional vibrational–electronic spectroscopy (i2D-VE). The fourth-order spectroscopy is based on a Mach–Zehnder IR interferometer that accurately controls the time delay of an IR pump pulse pair for vibrational transitions, followed by broadband interface second-harmonic generation to probe electronic transitions. We demonstrate step-by-step how a fourth-order i2D-VE spectrum of AP3 molecules at the air/water interface was collected and analyzed. The line shape and signatures of i2D-VE peaks reveal solvent correlations and the spectral nature of vibronic couplings. Together, i2D-VE and i2D-EV spectroscopy provide coupling of different behaviors of the vibrational ground state or excited states with electronic states of molecules at interfaces and surfaces. The methodology presented here could also probe dynamic couplings of electronic and vibrational motions at interfaces and surfaces, extending the usefulness of the rich data that are obtained. Full article

Purpose: Choroidal thickness (ChT) is an important measurement for evaluating eye and systemic disorders, but it is influenced by numerous elements, especially axial length (AL). It is known that the presence of a linear relationship between ChT and AL exists, but recently it has been shown that the AL measurement obtained with the current optical biometry is not very precise and needs to be corrected. This study aimed to verify if a similar correlation also persists with this corrected AL (ALc). Methods: All subjects underwent a complete eye examination, including spectral domain optical coherence tomography (OCT) with enhanced depth image (EDI) mode and AL measurement with IOLMaster. After a normality check of the data, the correlations between ChT with AL and ALc were investigated through the Pearson correlation coefficient. p values < 0.05 were considered statistically significant. Results: In total, 100 eyes of 50 healthy patients were evaluated. The mean AL was 24.36 ± 1.23 mm and mean ALc was 24.25 ± 1.22 mm. The mean nasal ChT, subfoveal ChT, and temporal ChT were, respectively, 250.57 ± 93.93 µm, 307.18 ± 101.66 µm, and 313.72 ± 88.86 µm. A significant negative linear correlation was found by comparing both AL and ALc to ChT (all r < −0.500, all p < 0.050). The negative linear correlation was stronger between nasal ChT and both AL and ALc (all r = −0.581). Conclusions: Through OCT and optical biometry, we confirmed that a statistically significant correlation persists between ALc and ChT, equal to the uncorrected AL. On these bases, in ChT studies or protocols, we recommend stratifying population according to ALc because linear correlation is still present; however, the cut-off values should be changed according to the systematic errors in optical biometry. In addition, both AL and ChT changes should be evaluated according to ALc. Full article

Background/Objectives: The interphotoreceptor matrix proteoglycans 1 and 2 (IMPG1 and IMPG2) are two interdependent proteoglycans of the interphotoreceptor matrix (IPM). Mutations in IMPG1 or IMPG2 are linked to retinal diseases such as retinitis pigmentosa (RP) and vitelliform macular dystrophy (VMD), yet the specific mutations responsible for each condition remain undefined. This study identifies mutations in IMPG1 and IMPG2 linked to either RP or VMD. It also provides an in-depth in silico analysis of these mutations’ structural and functional impact on protein domains, alongside a detailed examination of the corresponding disease phenotypes. Methods: From a cohort of 480 patients with inherited retinal diseases (IRDs), we identified seven patients with mutations in IMPG1 or IMPG2. Multimodal imaging was performed to assess the clinical phenotypes, including fundus photography, fundus autofluorescence, fluorescein angiography, and spectral domain optical coherence tomography (SD-OCT). We provide structure modeling and analysis of each variant. Results: Our findings indicate a prevalence of 1.45% of IRD patients being affected by IMPG mutations; two were diagnosed with RP and five with VMD. One VMD patient carried a novel IMPG1 p.Asp423Glu mutation. Most patients exhibited heterozygous mutations, and one RP patient presented a compound heterozygous mutation in IMPG2. Conclusions: This work describes a novel mutation and expands our understanding of the specific IMPG protein domains implicated in RP and VMD. Furthermore, it establishes, for the first time, the prevalence of IMPG mutations in an IRD population. Full article

A low-cost, wavelength-tunable single-longitudinal-mode (SLM) thulium–holmium co-doped fiber laser (THDFL) in a 2 μm band with a simple structure is described in the present paper. To obtain a stable SLM and narrow laser linewidth, a five-coupler-based three-ring (FCTR) filter is utilized in the ring cavity of the fiber laser. Tunable SLM wavelength output from THDFLs with kHz linewidths can be achieved by designing the FCTR filter with an effective free-spectral range and a 3 dB bandwidth at the main resonant peak. The measurement results show that the laser is in the SLM lasing state, with a highly stabilized optical spectrum, a linewidth of approximately 9.45 kHz, an optical signal-to-noise ratio as high as 73.6 dB, and a relative intensity noise of less than −142.66 dB/Hz. Furthermore, the wavelength can be tuned in the range of 2.6 nm. The proposed fiber laser has a wide range of applications, including coherence optical communication, optical fiber sensing, and dense wavelength-division-multiplexing. Full article

Background/Objectives: Inherited retinal diseases (IRDs) represent a diverse group of genetic disorders characterized by degeneration of the retina, leading to visual impairment and blindness. IRDs are heterogeneous, sharing common clinical features that can be difficult to diagnose without knowing the genetic basis of the disease. To improve diagnostic accuracy and advance understanding of disease mechanisms, genetic testing was performed for 103 unrelated patients with an IRD at a single clinical site between 30 August 2022 and 5 February 2024. Methods: Informed consent was obtained before buccal samples were collected for panel-based sequencing at BluePrint Genetics (BpG), sponsored by the Foundation Fighting Blindness MyRetina Tracker program. A retina specialist performed standard visit assessments, including visual acuity (Snellen chart), slit lamp examination, fundus photography (Optos^®, Dunfermline, UK), and spectral-domain optical coherence tomography (SD-OCT; Zeiss). Results: From 103 patients, genetic findings were reported for 70 individuals. Among these included 20 novel variants. Conclusions: These results clarify and confirm clinical diagnoses, aid in counseling patients on prognosis and family planning, and guide treatment options. This study not only holds promise for affected individuals but also expands the mutation spectrum to guide understanding of IRD. Full article

Background: To investigate functional and anatomical outcomes after pars plana vitrectomy (PPV) for lamellar macular hole (LMH) with a long-term follow-up. Methods: An interventional study on 14 patients (16 eyes) with LMH was conducted. The inclusion criteria included a minimum 36-month follow-up after PPV. The preoperative and postoperative best-corrected visual acuity (BCVA) and spectral domain optical coherence tomography parameters were examined. Results: Preoperatively, the mean BCVA was 0.46 ± 0.22 LogMAR. Epiretinal proliferation (ERP) was visible in 81.25% of eyes. Outer retinal disruption was present in 31.25% of LMH cases. The average central foveal thickness (CFT) measured 183.68 ± 61.73 microns. The mean BCVA improved at each follow-up time point: it was 0.24 ± 0.16 LogMAR at 1 month, 0.18 ± 0.15 LogMAR at 6 months, and 0.09 ± 0.11 LogMAR at the last follow-up. There was a statistically significant improvement between BCVA at 1 month and BCVA at 6 months and between BCVA at 6 months and BCVA at the last follow-up (p < 0.001). BCVA improved in all eyes, with 87.5% achieving at least 0.3 LogMAR improvement. The mean CFT at the 1-month follow-up was 211.45 ± 43.55 microns, increased to 248.81 ± 48.51 microns at 6 months, and further increased to 278.37 ± 45.50 microns at the last follow-up. Foveal contour restoration was achieved in all eyes, and those with preoperative ellipsoid zone alterations demonstrated a complete repair of the external retinal layers. No intra or postoperative complications were recorded. Conclusions: In our series, PPV had a high success rate and was associated with a substantial functional improvement in LMH treatment, and this result was maintained and kept increasing until the last follow-up. Long-term follow-up is crucial for a comprehensive evaluation of the healing process and to assess the benefits of the surgical intervention. Full article

Objectives: The objectives of this study were to evaluate the structural and functional outcomes after the loading phase with brolucizumab in switched patients with diabetic macular edema (DME) and to identify potential predictive biomarkers of treatment response. Methods: A total of 28 eyes with DME, switched to brolucizumab, were retrospectively reviewed. Main outcomes during the follow-up period, up to 6 weeks after the fifth injection, included changes in best-corrected visual acuity (BCVA), central subfield thickness (CST), macular volume, subfoveal choroidal thickness, intraretinal and subretinal fluid (IRF and SRF), cyst dimension including maximal horizontal cyst diameter (MHCD), maximal vertical cyst diameter (MVCD), width-to-height ratio (WHR), foveal avascular zone (FAZ) dimension, and vessel density (VD). Results: At the last follow-up, BCVA was significantly improved (p = 0.003). Significant reduction of CST was demonstrated after each injection time point (p < 0.05), and a dry macula was detected in 64.3% of patients at the last follow-up. The WHR was 1.23 ± 0.46, and a negative correlation to final CST (p < 0.0001) was found. In FAZ and VD analysis, no significant variation was detected. At the last disease activity assessment, the treatment regimen was q12 in 64% of patients. Conclusions: Brolucizumab leads to anatomical and functional improvements in switched eyes affected by DME. WHR may represent a predictive biomarker of treatment response. Full article

Myopic eye growth induces mechanical stretch, which can lead to structural and functional retinal alterations. Here, we investigated the effect of lens-induced myopic growth on the distribution of retinal ganglion cells (RGCs), glial fibrillary acidic protein (GFAP) expression and intensity, and peripapillary retinal nerve fiber layer (ppRNFL) thickness in common marmosets (Callithrix jacchus) induced with myopia continuously for six months, using immunohistochemistry and spectral-domain optical coherence tomography. We also explored the relationship between cellular structural parameters and the photopic negative response (PhNR) using full-field electroretinography. Marmosets induced with myopia for six months developed axial myopia, had a thinner ppRNFL, reduced peripapillary ganglion cell (≈20%) and astrocyte density (≈42%), increased panretinal GFAP expression (≈42%) and nasal mid-periphery staining intensity (≈81%) compared to age-matched controls. Greater degrees of myopia and vitreous elongation were associated with reduced peripapillary RGCs and astrocyte density, and increased GFAP expression and intensity. These cellular structural changes did not show a significant relationship with the features of the PhNR, which remained unchanged. The outcomes of this study suggest that myopia induces a reorganization of the peripapillary inner retina at the cellular level that may not result in measurable functional repercussions at this stage of myopia development. Full article

Here, we report a numerical study of supercontinuum generation in an antiresonant optical fiber with a hollow core filled with a mixture of deuterium (D₂) and hydrogen (H₂). For 1 ps pulses at a wavelength of 1.03 μm with different chirp values, we demonstrate a possibility of obtaining a mid-IR coherent supercontinuum with a spectral width of 2300 nm, initiated by cascade processes at resonance frequencies of vibrational and rotational levels of D₂ and H₂. We show that an increase in the chirped pulse duration to 25 ps while maintaining the energy and spectral width allows increasing the quantum conversion efficiency in the mid-IR from 10 to 50% and expanding the range of optimal fiber lengths at which a high degree of supercontinuum coherence is achieved. Full article

Colorectal cancer is one of the most prevalent forms of cancer globally. The most common routine diagnostic methods are the examination of the interior of the colon during colonoscopy or sigmoidoscopy, which frequently includes the removal of a biopsy sample. Optical methods, such as Raman spectroscopy (RS) and optical coherence tomography (OCT), can help to improve diagnostics and reduce the number of unnecessary biopsies. For in vivo use, we have developed fiber-optic probes, one for single-point Raman measurements and one for volumetric OCT. Here, we present the results of a clinical study using these fiber-optic probes in an ex vivo setting. The goal was to evaluate the beneficial effect of combining these two modalities on the AUC ROC score of the machine learning models for the discrimination of cancerous and healthy tissue. In the initial stage of the investigation, both modalities were validated separately using linear discriminant analysis. RS was subjected to spectral preprocessing, while OCT underwent texture feature extraction. Subsequently, both modalities were integrated using the Bayes rule, resulting in an enhanced area under the curve score of 0.93, representing an improvement over the 0.77 score for Raman spectroscopy and 0.86 for OCT. Full article

A novel class of random sources with a twisted multi-cosine Gaussian Schell model correlation function is introduced, termed the TMCGSM array. The spectral density and spectral degree of coherence of the TMCGSM array field upon propagation are investigated thoroughly. Numerical examples illustrate that such beams are capable of producing a non-uniform lattice profile in the far zone and exhibits an unusual rotation behavior. It is revealed that the twist factor can not only induce the array to rotate as a whole, but also has a modulation effect on the intensity of element lobes in the central area. We also demonstrated that an obvious twist effect could be observed in the coherence curves under certain conditions. Full article

Neuro-ophthalmological changes have been reported after prolonged exposure to microgravity; however, the pathophysiology remains unclear. Furthermore, several countermeasures have been suggested to counteract the side effects of microgravity. The objectives of the present study were twofold: (1) to assess the neuro-ophthalmological impact of 60 days of head-down bed rest (HDBR) and (2) to determine the potential effects of an antioxidant cocktail. In this case, 20 healthy male subjects completed a 60-day HDBR and were randomly allocated into two groups: a control condition without an antioxidant cocktail (CON) and a condition with an antioxidant cocktail (NUT). The retinal nerve fibre layer thickness (RNFLT) and central retinal thickness (CRT) were assessed with spectral domain optical coherence tomography. The optic nerve sheath diameter (ONSD) was measured by ocular ultrasonography and used to assess indirect changes in the intracranial pressure (ICP). The intraocular pressure (IOP) was assessed by Goldmann applanation tonometry. The CRT tended to be reduced after HDBR. The ONSD was increased at the end and after HDBR. The IOP tended to decrease after HDBR. Finally, the antioxidant cocktail had minor impacts on the ophthalmological changes induced by HDBR. It is worth noting that two participants presented peripapillary edema. Full article

Since the advent of Fourier Domain Mode-Locked (FDML) lasers, they have demonstrated outstanding performance in several fields. They achieve high-speed, narrow-linewidth laser output with the new mode-locking mechanism, which has been intensively researched in the past decades. Compared with conventional wavelength-scanning light sources, FDML lasers have successfully increased the scanning rate of frequency-sweeping lasers from kHz to MHz. They are widely used in optical coherence tomography, spectral analysis, microscopy, and microwave photonics. With the deepening research on FDML lasers, several performance metrics have been optimized and improved, offering superior performance for FDML laser-based applications. This paper reviews the principles and key performance indicators of FDML lasers, as well as the recent progress made in some important applications, and highlights further research directions for FDML lasers in the future. Full article