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Corneal structure, transparency, thickness and optical density (densitometry), especially as relevant to contact lens wear—a review
摘要： Clinical instruments using Scheimpflug image-based methods to obtain optical sectional images of the cornea have been introduced in recent years along with proposals that it should be possible to routinely and reliably measure the optical density (referred to as the densitometry) of the human cornea in situ. Such a concept is reviewed from the perspective of what might be considered as the basic principles underlying the understanding of corneal transparency (from the 1950’s) and the progressive changes in these ideas from subjective slitlamp-based clinical observations from the late 1960’s, especially in contact lens wearers. Much more has been learned about the overall macrostructure (including corneal thickness) and the ultrastructure of the cornea from contemporary studies in the 1990’s, and these aspects of the cornea will be reviewed alongside consideration of the methods of assessing the optical characteristics of the cornea in the living eye. From these perspectives, in this review systematic consideration will be given to what objective (quantitative) output one of these Scheimpflug-based systems provides and how this information might be actually related to corneal transparency characteristics that might be observed clinically, particularly after long-term contact lens wear.
关键词： Corneal opacities,Corneal swelling,Contact lens wear,Corneal densitometry,Corneal oedema,Human,Corneal
更新于2025-09-10 09:29:36
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Design of a frequency spectrum-based versatile two-dimensional arbitrary shape filter bank: application to contact lens detection
摘要： A filter bank (FB) is an integral part of any image processing system. The designing of a FB generally involves modifying an existing FB or focusing on a particular property of the filter bank. Such FBs limit their use to a particular image. Through our work, we have devised a unique and novel approach for designing a two-dimensional arbitrary shape filter bank (2-D ASFB). This FB is inherently 2-D and eliminates the need for transforming a one-dimensional FB into 2-D. Its arbitrary nature expands its application to any image as compared to regular-shaped FBs currently in use. The novelty of the design lies in the fact that the designed FB can match the frequency spectrum of any image by reducing the error function between the frequency spectrum and the desired filter response of the FB. The error function has been minimized using the eigenfilter approach. After designing the low-pass analysis filter, perfect reconstruction constraint has been used to get a low-pass synthesis filter. In this paper, we have demonstrated the use of the 2-D ASFB specifically for contact lens detection (CLD). The proposed CLD system focuses on feature extraction using the 2-D ASFB. The support vector machine classifier is the same as in the existing systems. The results show improved correct classification rate as compared to the existing systems for IIITD and ND2013 contact lens database. This 2-D ASFB overcomes limitations posed by the existing filter banks with respect to separability, directionality, orthogonality, and shape. This FB can be effectively applied to any feature extraction application such as pattern recognition, biometrics, medical image processing.
关键词： Eigenfilter,Contact lens detection,Feature extraction,Filter bank,Frequency spectrum
更新于2025-09-09 09:28:46
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Evaluation of corneal optical properties in subjects wearing hydrogel etafilcon A contact lenses and the effect of administering mannitol-enriched sodium hyaluronate ophthalmic solution
摘要： The purpose of this study was to evaluate the effect of daily administration of mannitol-enriched sodium hyaluronate ophthalmic solution on the corneal optical properties of subjects wearing low Dk hydrogel (etafilcon A) contact lenses (CLs). Forty-five subjects wearing etafilcon A CLs daily for more than 6 months were recruited into this pilot study. Fifteen of the subjects administered a 10% mannitol-enriched 0.05% sodium hyaluronate solution (study group) once daily and 30 subjects did not administer any ophthalmic solution (control group). The subjects were examined at baseline and one month after recruitment. Changes in central corneal thickness (CCT) and corneal light backscatter were evaluated by Scheimpflug imaging (Pentacam HR). Changes in corneal total high-order aberration, corneal spherical aberration, coma, and trefoil were evaluated using the OPD scan II. At one month, corneal light backscatter decreased significantly in the study group (#18.30 arbitrary units; P,0.05) and this was highly correlated with a decrease in CCT (R=0.81; P=0.04). The decrease in corneal total high-order aberration, spherical aberration, and coma was significantly higher in the study group than in the control group (P,0.05). No changes in corneal light backscatter or CCT were found in the control group during follow-up. Once-daily administration of a mannitol-enriched lubricant ophthalmic solution was effective for improving the corneal optical quality and reducing corneal swelling in subjects wearing low Dk hydrogel (etafilcon A) CLs during one month follow-up.
关键词： Scheimpflug imaging,corneal optical quality,corneal backscattering,corneal high-order aberrations,contact lens,hypertonic lubricant solution
更新于2025-09-09 09:28:46
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Extended Release of an Anti–Heparan Sulfate Peptide From a Contact Lens Suppresses Corneal Herpes Simplex Virus-1 Infection
摘要： PURPOSE. To prolong the release of a heparan sulfate binding peptide, G2-C, using a commercially available contact lens as a delivery vehicle and to demonstrate the ability of the released peptide to block herpes simplex virus-1 (HSV-1) infection using in vitro, ex vivo, and in vivo models of corneal HSV-1 infection. METHODS. Commercially available contact lenses were immersed in peptide solution for 5 days prior to determining the release of the peptide at various time points. Cytotoxicity of the released samples was determined by MTT and cell cycle analysis, and the functional activity of the released samples were assessed by viral entry, and viral spread assay using human corneal epithelial cells (HCE). The ability to suppress infection in human and pig cornea ex vivo and mouse in vivo models were also assessed. RESULTS. Peptide G2-C was released through the contact lens. Following release for 3 days, the peptide showed significant activity by inhibiting HSV-1 viral entry and spread in HCE cells. Significant suppression of infection was also observed in the ex vivo and in vivo experiments involving corneas. CONCLUSIONS. Extended release of an anti–HS peptide through a commercially available contact lens can generate significant anti–HSV-1 activity and provides a new and effective way to control corneal herpes.
关键词： virus infection,corneal epithelium,peptide,contact lens
更新于2025-09-09 09:28:46
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Thermo‐sensitive nanogel‐laden bicontinuous microemulsion drug‐eluting contact lenses
摘要： The bicontinuous microemulsion contact lens (BMCL) has nanoporous biphasic structures (100–250 nm) that are interconnected via multiple nano-channels, providing suitable retention of various drugs for glaucoma. Timolol maleate (TM)-carried poly(N-isopropylacrylamide) (PNIPAM) nanogel (30–50 nm) was incorporated into BMCLs by soaking or by centrifuging plus soaking. Here, we present drug-loading and release in silicon- or polyethylene oxide-microemulsion BMCLs under various conditions. Nanoporous BMCLs containing thermosensitive TM-laden nanogel were capable of potent body-temperature-triggered release of TM. Daily drug release was controllable according to the initial volume of drug-loaded (VDL) and loading method for sustained drug release, making them reduce drug-loss during transportation or storage.
关键词： temperature-triggered drug release,sustained drug release,bicontinuous microemulsion,drug delivery,nanoporous contact lens,drug-eluting contact lens
更新于2025-09-04 15:30:14
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Contact Lenses || Contact Lens Materials
摘要： The chapter provides an overview of contact lens materials, focusing on their development, properties, and the ocular response they elicit. It discusses the evolution from glass and PMMA to silicone hydrogels, highlighting the importance of oxygen permeability, wettability, and mechanical properties in lens design. The chapter also explores the challenges in achieving biocompatibility and comfort, the impact of lens materials on ocular health, and the future directions in materials development to address issues like dry eye and the ageing ocular surface.
关键词： Oxygen Permeability,Dry Eye,Ocular Response,Ageing Anterior Eye,Silicone Hydrogels,Contact Lens Materials,Biocompatibility
更新于2025-09-04 15:30:14
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Cross-sensor iris spoofing detection using orthogonal features
摘要： Iris recognition systems face issues related to spoo?ng attacks that obfuscate the natural iris texture pattern. This makes it a challenging problem to be used for large-scale high security applications. The paper introduces a rotation-invariant feature-set comprising of Zernike moments and Polar harmonic transforms that extract local intensity variations for detection of iris spoo?ng attacks. Experimental results have been implemented on four publicly available iris spoo?ng databases: IIITD Contact Lens, IIITD Iris Spoo?ng, Clarkson LivDet-Iris 2015 and Warsaw LivDet-Iris 2015 that include both contact lens and print attack spoo?ng samples. Experiments demonstrate that the proposed system easily detects spoo?ng attacks even when acquired using multiple sensors.
关键词： Iris spoo?ng,Zernike moments,Print attacks,Contact lens,Polar harmonic transforms
更新于2025-09-04 15:30:14