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Objective: Unknown etiology Background: This case report illustrates the incidental detection of atypical hyporeflective bleb-like structures in an otherwise asymptomatic human cornea, highlighting the effectiveness of non-invasive biophotonic imaging techniques such as optical coherence tomography (OCT) and large-area confocal laser scanning microscopy (CLSM). Case Report: A 57-year-old man underwent a comprehensive ophthalmological examination, including slit-lamp biomicroscopy, corneal topography, and densitometry, as part of a clinical study. The patient presented with a clear cornea, a deep and optically empty anterior chamber, and a clear crystalline lens in both eyes. Best-corrected distance visual acuity was -0.1 logMAR. He denied ocular pain, tearing, or photophobia. There was no history of ocular trauma, infectious or genetic diseases, or ocular surgery. Further, OCT and large-area CLSM were employed for a more in-depth analysis of the corneal structure. Standard ophthalmological assessments indicated normal ocular health with no apparent corneal abnormalities. High-resolution OCT and large-area CLSM imaging revealed atypical hyporeflective bleb-like structures within the corneal epithelium and sub-basal nerve plexus but not in the stroma. Conclusions: The authors hypothesize that the observed findings may indicate an early stage of epithelial basement membrane dystrophy, potentially preceding the manifestation of clinical symptoms, detectable solely through advanced biophotonic imaging methods. It is important to emphasize that these observations do not represent a definitive diagnosis. Nevertheless, the discovery of these atypical structures via advanced imaging underscores the importance of incorporating non-invasive biophotonic techniques into preoperative eye examinations in certain situations. This approach could significantly improve the early detection and management of corneal diseases, leading to improved patient outcomes. [ABSTRACT FROM AUTHOR]

Hydrogels were introduced as suitable materials for applications in, e.g., medical, agriculture, or daily life areas. Swelling characteristics of a hydrogel are important and must be precisely known for various fields of application. In medicine, where hydrogels are used as implants or drug delivery systems, precise knowledge of the swelling behavior is essential. Especially in ophthalmology as part of cataract surgery, the visco‐elastic properties of the hydrogels could even allow for the restoration of accommodation. The easiest way to describe the swelling is by measuring the swelling ratio, generally done by scaling. Besides that, it can also be done by volume investigations. The similarities and differences are studied on five hydrogel samples made of methyl methacrylate and N‐vinyl pyrrolidone. Additionally, a first camera‐based approach, potentially providing an automated, quasi‐continuous non‐contact method for swelling kinetics investigations, is described. [ABSTRACT FROM AUTHOR]

Nowadays, CCD cameras can be found in every optical laboratory for highly diverse purposes. Measuring quantitatively spectral-dependent intensities implies that the spectral quantum efficiency (SQE) has to be taken into account, at least if the width of the spectrum is more than a few nm. The determination of the SQE is usually considered to be a tedious challenge with rather inaccurate results. However, we show in this paper that with calibrated photo diodes, this has become an affordable and straightforward task. In this paper, we examined the SQE of one front- and five back-illuminated electron multiplying CCD cameras from Andor Technology in the range of 350–1080 nm with a spectral resolution of up to 1 nm. The temperature dependence of the SQE has been investigated in the spectral interval given above between +20 and −80 °C. We observed unexpected oscillations in the SQE for the front-illuminated camera. For back-illuminated cameras with an ultraviolet conversion layer, the measured SQE turns out to be very different from the manufacturer data, which results from the transmittance spectrum of the conversion layer. For conventional back-illuminated cameras without a conversion layer, we observed interesting crossing behavior in the temperature-dependent measurements. [ABSTRACT FROM AUTHOR]

Use of Brillouin spectroscopy in ophthalmology enables noninvasive, spatially resolved determination of the rheological properties of crystalline lens tissue. Furthermore, the Brillouin shift correlates with the protein concentration inside the lens. In vitro measurements on extracted porcine lenses demonstrate that results obtained with Brillouin spectroscopy depend strongly on time after death. The intensity of the Brillouin signal decreases significantly as early as 5 h postmortem. Moreover, the fluctuation of the Brillouin frequency shift inside the lens increases with postmortem time. Images of lens tissue taken with a confocal reflectance microscope between measurements reveal a degenerative aging process. These tissue changes correlate with our results from Brillouin spectroscopy. It is concluded that only in vivo measurements appropriately reflect the rheological properties of the eye lens and its protein concentration. [ABSTRACT FROM PUBLISHER]

Background: The in vivo characterisation of corneal epithelial tissue morphology is of considerable importance for diagnosis, disease prognosis, and the development of a treatment strategy for ocular surface diseases. In contrast to many alternative methods, in vivo corneal confocal microscopy (CCM) not only provides a macroscopic description of the corneal tissue but also allows its visualisation with cellular resolution. However, the translation of CCM from research to clinical practice is significantly limited by the complex and still largely manual operation of available CCM systems. In addition, for cross-sectional images, and analogously to conventional slit lamp microscopy, volume data must be acquired in time-consuming depth scans due to the frontal orientation of the image field in CCM, from which depth slices can subsequently be calculated. The pure acquisition time is already in the range of seconds, and additionally, motion artefacts have to be corrected in a sophisticated way., Materials and Methods: This paper presents the concept and optics simulation of a new imaging technique based on a swept-source laser in combination with special chromatic optics. Here, the laser periodically changes its wavelength and is focused at different depths due to the wavelength-dependent aberration of the chromatic optics., Results: The optics simulation results promise good optical resolution at a total imaging depth of 145 µm., Conclusion: The long-term goal is cell-resolving in vivo corneal confocal microscopy in real time with differently oriented sectioning directions., Competing Interests: Die Autoren Allgeier und Reichert erklären, dass sie keine Interessenkonflikte haben. Die Autoren Sperlich, Bohn, Stolz, Guthoff und Stachs erklären, als Erfinder in einer Patentanmeldung der Universität Rostock aufgeführt zu sein, welche das hier vorgestellte Verfahren beschreibt., (Thieme. All rights reserved.)

To assess the structural integrity of the cornea, non-invasive methods are needed for the local measurement of its mechanical properties. Among a number of established techniques and their associated advantages and disadvantages, Brillouin spectroscopy is still a relatively new technique, capable of determining the compressive modulus of biological tissue, specifically the cornea, in vivo. In the present paper, these various existing and developing technologies for corneal biomechanics are discussed and correlated., Competing Interests: Die Autorinnen/Autoren geben an, dass kein Interessenkonflikt besteht., (Thieme. All rights reserved.)

Background: For quantitative and qualitative evaluation of the imaging properties of IOLs, axial cross-sectional images can be obtained from the 3-dimensional light distribution by means of an optical bench, as is known from light sheet recordings in fluorescein baths. This paper presents a new image-processing algorithm to enhance the quality of generated axial cross-sectional images, and the two methods are then compared., Material and Methods: The 3-dimensional point spread function of a diffractive trifocal IOL (AT LISA tri 839MP, Carl Zeiss Meditec AG, Jena, Germany) was recorded on an optical bench developed in Rostock for different pupil diameters. A specially adapted image processing algorithm was then applied to the measurements, allowing through-focus curves to be generated. In addition, cross-sectional images of the IOLs studied were acquired using the light sheet method in a fluorescein bath., Results: The study clearly shows the superiority of the newly developed method over the light sheet method in terms of image quality. In addition to the individual focal points, fine focal structures as well as halos can be made visible in the cross-sectional images obtained using the new method. In the generated through-focus curves, 3 intensity peaks can be identified, which represent the near, intermediate and far focus of the tested MIOL and cannot be represented by light sheet methods., Conclusion: The interaction of the optical bench with the developed image processing algorithm allows a more detailed understanding of the image formation and false light phenomena of IOLs, which was restricted by the technical limitations of the existing light sheet method. In addition, other quantities such as the through-focus curve can be derived quantitatively., Competing Interests: Die Autorinnen/Autoren geben an, dass kein Interessenkonflikt besteht., (Thieme. All rights reserved.)

The development of new optical designs for intraocular lenses (IOL) is a major challenge for lens manufacturers, as postoperative patient satisfaction is difficult to assess a priori with new concepts. Until now, invasive clinical investigations were carried out for this purpose. In contrast, the simulated implantation of IOLs allows a risk-free determination of the achievable visual performance and a subjective evaluation of the visual impression of new optical concepts. For intraocular lens manufacturers, this offers, on the one hand, the possibility to take the subjective perception of test persons into account during the development and optimization of novel lens designs and, on the other hand, to carry out comparative performance tests with known products before the first implantation. By means of simulated implantation, subjectively optimized IOLs may lead to a better postoperative visual quality for the patients and minimize the risk of a cost-intensive development of products with clinically unacceptable visual perception achievements due to optical side effects. The application of the simulated implantation during the preoperative patient consultation may enable the determination of the patient's subjective visual preferences and result in a targeted IOL selection recommendation. In addition to an improved selection from an existing IOL portfolio, IOL manufacturers could also offer individualized multifocal IOLs that match the patient's previous preference pattern. This article explains the technical background and application scenarios of the simulated implantation and introduces current procedures and devices., Competing Interests: Die Autoren geben an, dass kein Interessenkonflikt besteht., (Georg Thieme Verlag KG Stuttgart · New York.)

We present an in vivo confocal laser scanning microscopy based method for large 3D reconstruction of the cornea on a cellular level with cropped volume sizes up to 266 x 286 x 396 µm 3 . The microscope objective used is equipped with a piezo actuator for automated, fast and precise closed-loop focal plane control. Furthermore, we present a novel concave surface contact cap, which significantly reduces eye movements by up to 87%, hence increasing the overlapping image area of the whole stack. This increases the cuboid volume of the generated 3D reconstruction significantly. The possibility to generate oblique sections using isotropic volume stacks opens the window to slit lamp microscopy on a cellular level., Competing Interests: The authors declare that there are no conflicts of interest related to this article.

Elevated intraocular pressure (IOP) is accepted to be one important criterion for glaucoma and is usually measured by applanation or rebound tonometry. The individual uncertainty due to central cornea thickness (CCT) is thereby corrected, while the error induced by age-related elastic modulus (EM) change of the cornea is ignored. To investigate its influence on IOP measurement, we derive a model including also the elastic modulus. Our approach is based on known equations from experimental physics and several assumptions being justified in this paper. Our correction values are in good agreement with the Dresden correction table for low CCT values up to 650 µm using a mean EM of 0.29 MPa. An EM variation from 0.2 to 0.5 MPa, which relates to ages from infancy to 90 years, results in an IOP error of up to 10 mmHg. A variation of the cornea curvature from 7.4 mm to 8.0 mm results in a total IOP change of about 3 mmHg, which is usually neglected. The derived model shows that established correction formulas can be insufficient for a reliable IOP determination. In many cases, the conventionally measured IOP may be precise enough, but the uncertainty in IOP determination due to CCT and EM influence are almost in the same range. Measuring the IOP using applanation methods with established correction formulas should not be overestimated without to respect the EM of the cornea., Competing Interests: Interessenkonflikt: Die Autoren geben an, dass kein Interessenkonflikt besteht., (Georg Thieme Verlag KG Stuttgart · New York.)