Search Results (83)

This study describes and validates a novel method for assessing anterior crystalline lens curvature along vertical and horizontal meridians using radial measurements derived from Scheimpflug imaging. The aim was to evaluate whether pupil diameter (PD), anterior lens curvature, and anterior chamber depth (ACD) change during accommodation and whether these changes are age-dependent. A cross-sectional study was conducted on 104 right eyes from healthy participants aged 21–62 years. Sixteen radial images per eye were acquired using the Galilei Dual Scheimpflug Placido Disk Topographer under four accommodative demands (0, 1, 3, and 5 dioptres (D)). Custom software analysed lens curvature by calculating eccentricity in both meridians. Participants were analysed as a total group and by age subgroups. Accommodative amplitude and monocular accommodative facility were inversely correlated with age. Both PD and ACD significantly decreased with higher accommodative demands and age. Relative eccentricity decreased under accommodation, indicating increased lens curvature, especially in younger participants. Significant curvature changes were detected in the horizontal meridian only, although no statistically significant differences between meridians were found overall. The vertical meridian showed slightly higher eccentricity values, suggesting that it remained less curved. By enabling detailed, meridionally stratified in vivo assessment of anterior lens curvature, this novel method provides a valuable non-invasive approach for characterizing age-related biomechanical changes during accommodation. The resulting insights enhance our understanding of presbyopia progression, particularly regarding the spatial remodelling of the anterior lens surface. Full article

Purpose: Pellucid Marginal Degeneration (PMD) is a rare ectatic corneal disorder characterized by inferior peripheral thinning and significant irregular astigmatism. Despite its clinical similarities to keratoconus, PMD presents unique diagnostic and therapeutic challenges. This review aims to provide a comprehensive update on the pathophysiology, clinical features, diagnostic approaches, and management strategies for PMD, emphasizing the latest advancements in treatment options. Methods: A systematic literature search was performed in MEDLINE (via PubMed), Google Scholar, and Scopus up to February 2025 using the terms: “pellucid marginal degeneration,” “PMD,” “ectatic corneal disorders,” “keratoplasty in PMD,” “corneal cross-linking in PMD,” “ICRS in PMD,” “toric IOL PMD” and their Boolean combinations (AND/OR). The search was restricted to English-language studies involving human subjects, including case reports, case series, retrospective studies, clinical trials, and systematic reviews. A total of 76 studies met the inclusion criteria addressing treatment outcomes in PMD. Results: PMD is characterized by a crescent-shaped band of inferior corneal thinning, leading to high irregular astigmatism and reduced visual acuity. Diagnosis relies on advanced imaging techniques such as Scheimpflug-based corneal tomography, which reveals the characteristic “crab-claw” pattern. Conservative management includes rigid gas-permeable (RGP) lenses and scleral lenses, which provide effective visual rehabilitation in mild to moderate cases. Surgical options, such as CXL, ICRS, and toric IOLs, are reserved for advanced cases, with varying degrees of success. Newer techniques such as CAIRS, employing donor tissue instead of synthetic rings, show promising outcomes in corneal remodeling with potentially improved biocompatibility. Penetrating keratoplasty (PK) and deep anterior lamellar keratoplasty (DALK) remain definitive treatments for severe PMD, though they are associated with significant risks, including graft rejection and postoperative astigmatism. Conclusions: PMD is a complex and progressive corneal disorder that requires a tailored approach to management. Early diagnosis and intervention are critical to optimizing visual outcomes. While conservative measures are effective in mild cases, surgical interventions offer promising results for advanced disease. Further research is needed to refine treatment protocols and improve long-term outcomes for patients with PMD. Full article

This study proposes a deep learning-based, non-contact method for detecting elevated intraocular pressure (IOP) by integrating Scheimpflug images with corneal biomechanical features. Glaucoma, the leading cause of irreversible blindness worldwide, requires accurate IOP monitoring for early diagnosis and effective treatment. Traditional IOP measurements are often influenced by corneal biomechanical variability, leading to inaccurate readings. To address these limitations, we present a multi-modal framework incorporating CycleGAN for data augmentation, Swin Transformer for visual feature extraction, and the Kolmogorov–Arnold Network (KAN) for efficient fusion of heterogeneous data. KAN approximates complex nonlinear relationships with fewer parameters, making it effective in small-sample scenarios with intricate variable dependencies. A diverse dataset was constructed and augmented to alleviate data scarcity and class imbalance. By combining Scheimpflug imaging with clinical parameters, the model effectively integrates multi-source information to improve high IOP prediction accuracy. Experiments on a real-world private hospital dataset show that the model achieves a diagnostic accuracy of 0.91, outperforming traditional approaches. Grad-CAM visualizations identify critical anatomical regions, such as corneal thickness and anterior chamber depth, that correlate with IOP changes. These findings underscore the role of corneal structure in IOP regulation and suggest new directions for non-invasive, biomechanics-informed IOP screening. Full article

The purpose of this study is to evaluate the potential impact of small aperture optics on corneal aberrations in post-RK patients. Preoperative data was evaluated from 32 eyes of 23 post-RK patients. Scheimpflug tomography was used to obtain measurements of corneal HOAs at 6-mm, 4-mm, and 2-mm corneal plane aperture diameters. The data was extrapolated using a non-linear fit to estimate HOAs that would be obtained with the 1.6 mm effective pinhole IOL aperture at the corneal plane for individual patients. The average RMS HOAs estimated for the 1.6 mm aperture was 0.063 ± 0.015 μm compared to 0.185 ± 0.029 μm for the natural pupil size. A postoperative RK case with an IC-8^® Apthera™ unilateral implantation demonstrated a 70% reduction in HOAs by objective measurement and prediction, plus a 2-line improvement in CDVA. Prediction modeling revealed that HOAs may be reduced in post-RK patients following pinhole IOL implantation, compared to the natural photopic pupil size. Furthermore, the approach can be used to guide which post-RK patients would benefit from a small aperture IOL during cataract surgery. Full article

Common surface temperature measurement techniques, when applied to monitoring the temperature of surfaces with complex morphology, suffer from reduced spatial resolution, which compromises the measurement accuracy of the system. To improve the spatial resolution of temperature measurement technology and maintain high temperature sensitivity, we designed a microscopic morphology thermometric LiDAR (MMTL) system based on the Scheimpflug principle, which realizes the real-time restoration of the 3D morphology and temperature of the surface of micro-structured objects. The 3D spatial resolution of the system is better than 3 μm. The theoretical resolution of the self-designed reflective spectrometer can reach 0.9 nm, which improves the sensitivity and accuracy of the upconversion hybrid nanomaterials thermometry based on the intensity ratio. In the wide temperature range of 373.15–508.15 K, the highest relative temperature sensitivity can reach 2.07%/K, the optimal temperature resolution is 0.0131 K, and the error is less than 1 K. Finally, the temperature change trend of the mold surface under different heating voltages is accurately restored. The MMTL system can provide accurate temperature distribution data and hotspot location identification for scenarios such as optimizing thermal management design and real-time risk monitoring, and it has application potential in industrial manufacturing and for electronic products. Full article

Lidar has emerged as a pivotal technique within the booming field of plant phenotyping, which has seen significant advancements in recent years. Beyond the conventional LiDAR systems that determine distance based on time-of-flight principles, Scheimpflug LiDAR, an emerging technique proposed within the past decade, has also expanded its field to plant phenotyping. However, early applications of Scheimpflug LiDAR were predominantly focused on aerosol detection, where stringent requirements for range resolution were not paramount. In this paper, a detailed description of a Scheimpflug LiDAR designed for plant phenotyping is proposed. Furthermore, to ensure high-precision scanning of plant targets, a distance-adaptive Gaussian fitting methodology is proposed to improve the spatial precision from 0.1781 m to 0.044 m at 10 m, compared with the traditional maximum method. The results indicate that the point cloud data acquired through our method yield more precise phenotyping outcomes, such as diameter at breast height (DBH) and plant height. This paves the way for further application of the Scheimpflug LiDAR on growth stages monitoring and precision agriculture. Full article

Background/Objectives: To evaluate the timing and extent to which late keratometric changes can occur between year 7 and 12 after corneal collagen crosslinking (CXL) in patients with keratoconus. Methods: A subgroup of a retrospective cohort study of all consecutive patients who underwent CXL at our cornea center between 2007 and 2011 was analyzed. The inclusion criteria consisted of CXL according to the Dresden protocol and a full set of keratometry parameters collected by Scheimpflug tomography preoperatively and at year 7, 9 and 12 after CXL. Results: A total of 46 eyes of 35 patients were included. The most relevant keratometric parameters (Kmax, TCT, K1, K2 and anterior astigmatism) decreased statistically significantly at year 7 after CXL, while there was no relevant difference for posterior astigmatism and the flat axes of anterior and posterior astigmatism. All keratometric parameters (except for K2) remained stable between year 7 and 12 without statistically significant change, according to mixed effect model regression analysis. BCVA improved statistically significant between the baseline and year 7 and remained stable until year 12. Suspected disease progression was noted in two patients (4.3%) between year 7, 9 and 12 post-CXL. Conclusions: Keratometric and functional results improve significantly 7 years after CXL in comparison to preoperative values and show very effective stabilization without clinically relevant changes up to year 12. However, while the risk of disease progression decreases remarkably after 7 years, in rare cases, suspected progression can occur even up to year 12. Therefore, regular control visits with keratometry measurements are advisable at least every 2 to 3 years in the late postoperative course. Full article

Background/Objectives: Childhood obesity is a significant health concern also capable of impacting ocular health. This study evaluates the effects of childhood obesity on corneal morphology, anterior chamber parameters, intraocular pressure (IOP), and corneal endothelial cell morphology. Understanding these relationships may contribute to early diagnosis and management strategies. Methods: This prospective, cross-sectional study was conducted at the Harran University Faculty of Medicine between January and December, 2024. Ninety children aged 7–17 years were included, with only the right eyes being analyzed. The participants were categorized into three groups based on body mass index (BMI) percentiles: normal weight (≤85th percentile), overweight (86–94th percentiles), and obese (≥95th percentile). All participants underwent comprehensive ophthalmological examinations, including IOP measurement with a non-contact tonometer, corneal topography assessment using a Scheimpflug camera, and endothelial cell morphology evaluation via specular microscopy. Results: IOP was significantly higher in the overweight and obese groups (p < 0.001). Central corneal thickness (CCT) also increased significantly in these groups (p < 0.05). Positive correlations were determined between BMI and IOP (r = 0.493, p < 0.001) and CCT (r = 0.345, p < 0.001). Additionally, waist circumference exhibited a strong correlation with BMI (r = 0.905, p < 0.001) and a significant association with IOP (r = 0.463, p < 0.001). No significant differences were observed among the groups in terms of other anterior chamber or endothelial parameters. Conclusions: Childhood obesity is associated with increased IOP and CCT, suggesting potential alterations in corneal biomechanics and ocular physiology. These findings highlight the importance of routine ophthalmological evaluation in obese children to detect early ocular changes and prevent long-term complications. Full article

We aimed to determine the effects of night-shift work on corneal parameters in thirty-five healthy individuals (24–59 years) in a retrospective cohort study. Among them, 12 hospital nurses regularly worked two shifts, spending a third of their nights awake, whereas 23 age-matched controls never worked shifts and slept regularly. Measurements were performed at least five times within 12 h. We analyzed the keratometric parameters of the corneal front (F) and back (B) surfaces, including the refractive power in the flattest and steepest axes (K1, K2), astigmatism (Astig); and corneal pachymetry (Pachy) at the thinnest corneal point and pupil center, volume relative to the 10 mm corneal diagonal (Vol D10); and surface variance index (ISV). A multilevel mixed-effects linear regression adjusted for age was applied to 905 measurements. All parameters exhibited significant periodic fluctuations (p ≤ 0.005). The two groups also showed significantly different periodic fluctuations (p ≤ 0.008), except in K1B and AstigB. K1/K2 (F and B), AstigF, Pachy, and ISV differed significantly (p < 0.0001). Surprisingly, prolonged night shift work did not increase the ISV, and no evidence of age-related corneal thinning was observed. Long-term night-shift exposures change various corneal parameters, reflecting both concomitant and adaptive effects. This study highlights the impact of consistent sleep deprivation on corneal properties, warranting further research into understanding the long-term effects of night-shift work. Full article

Background/Objectives: The evaluation of the differences in corneal epithelial thickness profiles in healthy eyes and eyes with mild and moderate stages of keratoconus, using optical coherence tomography (OCT). Methods: Fifty-two healthy eyes (group 0), forty-one eyes with mild keratoconus (group I), and thirty eyes with moderate keratoconus (group II) were included in this study. Only one of the patient’s eyes was enrolled, and they were divided into groups using the Amsler–Krumeich (A–K) classification—stage I and II. All patients underwent a visual acuity assessment, slit-lamp examination, corneal tomography, and automatic mapping of corneal thickness and epithelial thickness on a diameter of 9 mm. Corneal tomography with a Placido/Scheimpflug instrument (Sirius, CSO, Florence, Italy) and OCT with a corneal adaptor module (Avanti RTVue XR, Optovue, Lombard, IL, USA) were used. Results: Minimum corneal epithelium thickness was 49.5, 43, and 40 µm in groups 0, I, and II, respectively (Kruskal–Wallis test, p < 0.001). A moderate correlation was found between minimum epithelial thickness and the apex curvature (Pearsons’s coefficient r = −0.62, p < 0.001) and posterior radius of central corneal curvature (Pearsons’s coefficient r = 0.62, p < 0.001). The difference between minimum and maximum epithelial thickness showed a high correlation (r = −0.770, p < 0.001). In groups I and II, on corneal epithelial thickness maps the thinnest sector, located inferiorly and temporally to the center, was surrounded by sectors with increased thickness. Conclusions: At the apex of the cone, the corneal epithelium becomes thinner, and a thicker ring forms around the cone. Although there is a moderate-to-strong correlation to parameters linked with the severity of keratoconus, and minimum epithelial thickness as well as the minimum–maximum difference, it is not possible to establish cut-off values for stages I and II in the Amsler–Krumeich (A–K) classification. Full article

Repeatable and reliable assessment of corneal biomechanics with spatial resolution remains a challenge. Vibrational Optical Computerized Tomography (V-OCT), based on sound-wave elastography, has made it possible to investigate the natural resonant modes of the cornea and obtain the elastic moduli non-invasively. This pilot study presents a characterization of four corneal vibrational modes from aberrometric, geometrical, and biomechanical approaches in the living human cornea of five healthy volunteers by combining a corneal sound-wave generator, dual Placido–Scheimpflug corneal imaging, and the Ocular Response Analyzer (ORA) devices. Sound-induced corneal wavefront aberration maps were reconstructed as a function of sound frequency and isolated from the natural state. While maps of low-order aberrations (LOA) revealed symmetric geometrical patterns, those corresponding to high-order aberrations (HOA) showed complex non-symmetric patterns. Corneal geometry was evaluated by reconstructing corneal elevation maps through biconical fitting, and the elastic and viscous components were calculated by applying the standard linear solid model to the ORA measurements. The results showed that sound-wave modulation can increase high-order corneal aberrations significantly. Two frequencies rendered the corneal shape more prolate (50 Hz) and oblate (150 Hz) with respect to the baseline, respectively. Finally, both the elastic and viscous properties are sensitive to sound-induced vibrational modes, which can also modulate the corneal stress-strain response. The cornea exhibits natural resonant modes influenced by its optical, structural, and biomechanical properties. Full article

Nitrogen dioxide (NO₂) is broadly acknowledged as one of the six key air pollutants, posing a significant threat to environmental stability and human health. The profile of atmospheric nitrogen dioxide is required for quantifying NO₂ emissions from fossil fuel combustion and industry. In continuous-wave differential absorption lidar (CW-DIAL) systems, the laser sources employed are subject to the issues of varying output characteristics and poor instability. This study presents a CW-DIAL system for remote sensing of atmospheric NO₂ that employs a compact grating-based external cavity diode laser (ECDL) and Scheimpflug imaging. The laser in this system utilizes a piezoelectric transducer (PZT) for precise wavelength tuning, emitting at 448.1 nm and 449.7 nm with an output power of 2.97 W and a narrow linewidth of 0.16 nm. Signal capturing was achieved through a Newtonian telescope with a diameter of 200 mm and a 45° inclined CCD image sensor, satisfying the Scheimpflug principle. A case study near road traffic was used to verify the feasibility of ECDL-DIAL, which took place from 1 October to 2 October 2023 over an industrial park. The system generates precise NO₂ distribution maps with sub-50 m resolution over 3 km, updating every 10 min. Full article

Background: This study aims to evaluate the repeatability of the Pentacam HR, comparing two different measurement modes (50-cornea fine and 25-3D scan) in patients affected by keratoconus. Methods: Multicenter retrospective study, conducted at Eye Clinic of the ASST-Spedali Civili-University of Brescia, Italy, and St. Paul’s Eye Unit, Royal Liverpool University Hospital, United Kingdom. A total of 72 eyes from 72 patients with keratoconus underwent six consecutive measurements, three using the 25-3D scan mode and three with the 50-Cornea fine mode. Measurements were made by one single observer, using the Scheimpflug corneal tomographer camera (Pentacam HR, Oculus, Wetzlar, Germany). Repeatability was assessed using the within-subject SD (S_w) statistic from a two-way analysis of variance. Results: Both measurement modes had excellent repeatability. The interclass coefficient correlation (ICC) was excellent (>0.9) in all the parameters evaluated, apart from anterior and posterior astigmatic axes and posterior astigmatism (ICC > 0.8) and index of height asymmetry (IHA) (ICC < 0.6). However, in 18 of 29 parameters, the ICC was higher in case of 25-3D scan. Repeatability limit for Kmax was 1.00D in 25-3D scan mode and 1.02D in case of 50-cornea fine. Conclusions: 25-3D scan may be preferable to 50-Cornea fine, in view of having slightly higher ICC in case of patients with keratoconus. Repeatability limits reported may be helpful in clinical practice for assessing the progression of keratoconus. Full article

Background/Objective: The aim of this retrospective study was to compare corneal parameters and compliance using a Pentacam HR–Scheimpflug (Pentacam HR) and a swept-source OCT Casia (Casia) in keratoconus (KC) patients post penetrating keratoplasty (PKP) and KC patients without PKP, as well as a control group. Pachymetry measurements were also analyzed using a spectral domain OCT Solix (OCT Solix), Pentacam HR, and Casia. Methods: The study included 71 patients (136 keratoconic eyes; group A), 86 eyes with KC post-PKP (group B), 50 eyes with KC without PKP (group C), and 52 control participants (104 eyes). All participants were adults, Polish Caucasian, and met specific inclusion criteria. Patients with ophthalmological or systemic diseases, cognitive impairment, or pregnancy were excluded. Corneal parameters were measured using two devices (Casia and Pentacam HR), while pachymetry was assessed with three devices (Casia, Pentacam HR, and OCT Solix), with the inter-device agreement and group differences analyzed. Results: Significant differences (p < 0.05) were found across all groups. The post-PKP KC eyes showed significant differences in all front parameters and K2 and Astig. back, while the non-PKP KC eyes showed differences in the K1 back (p = 0.025). The controls displayed differences in all parameters except front astigmatism (p = 0.61). The Pentacam HR overestimated the thinnest corneal thickness (TCT) compared to the OCT Casia across groups. The inter-device agreement was excellent for the anterior parameters (ICC > 0.9) but good for the posterior parameters and TCT. Conclusions: This study highlights significant variability in corneal and pachymetry measurements across devices, with OCT Casia providing more consistent and clinically reliable results than Pentacam HR. Clinicians should exercise caution when using these devices interchangeably, particularly for posterior parameters and TCT. Full article

Background/Objectives: To determine the impact of corneal and biometry parameters on the normative root mean square (RMS) values of corneal aberrations measured at a 6 mm diameter. Methods: The RMS values for corneal aberrations (anterior, posterior, and total) were measured along with corneal parameters using Scheimpflug tomography on 770 normal subjects. The biometric parameters were measured with an optical biometer. A multiple linear regression model was used to assess the effect of these parameters on the RMS values for corneal aberrations. Results: The mean RMS values for low-order (LOAs) and high-order 6 mm aberrations (HOAs) were 1.883 ± 0.797 µm and 0.484 ± 0.173 µm, respectively, and for the anterior and posterior cornea, the values were 0.775 ± 0.166 µm and 0.189 ± 0.036 µm, respectively. For the anterior cornea, the main predictors of the RMS LOAs (R² = 69.8%) were anterior corneal astigmatism (ACA) and anterior corneal elevation (Ele F) on the apex (both p < 0.0001) and for the RMS HOAs (R² = 33.3%) the main predictors were age, ACA, and Ele F on the thinnest point (all p < 0.0001). For the posterior cornea, considering only the posterior corneal variables, the main predictors of the RMS LOAs (R² = 63.4%) were posterior corneal astigmatism and posterior corneal elevation (Ele B) on the thinnest point and apex (all p < 0.0001) and for the RMS HOAs (R² = 46%) the main predictors were the mean posterior keratometry and Ele B on the thinnest point and apex (all p < 0.0001). Conclusions: Normative data of RMS values for corneal aberrations measured over 6 mm are influenced by age and several corneal parameters, which should be considered when evaluating the diagnostic ability of the RMS values. Full article