Biomedical subjects

Oliver Stachs

Publications and source records attributed to Oliver Stachs.

7 recordsLinked to original sources

PubMed2006

In vivo three-dimensional confocal laser scanning microscopy of the epithelial nerve structure in the human cornea.

PURPOSE: Evaluation of a new method for in vivo visualization of the distribution and morphology of human anterior corneal nerves. METHOD: The anterior cornea was examined to a depth of 100 microm in four human volunteers with a confocal laser scanning microscope (CLSM) using a Rostock Cornea Module (developed in house) attached to a Heidelberg Retina Tomograph II (Heidelberg Engineering, Germany). Optical sections were digitally reconstructed in 3D using AMIRA (TGS Inc., USA). The scanned volumes had a greatest size of 300 x 300 x 40 microm and voxel size of 0.78 x 0.78 x 0.95 microm. RESULTS: The spatial arrangement of the epithelium, nerves and keratocytes was visualized by in vivo 3D-CLSM. The 3D-reconstruction of the volunteers' corneas in combination with the oblique sections gave a picture of the nerves in the central human cornea. Thin nerves run in the subepithelial plexus aligned parallel to Bowman's layer and are partially interconnected. The diameter of these fibres varied between 1.0 and 5 microm. Thick fibres rose out of the deeper stroma. The diameter of the main nerve trunks was 12+/-2 microm. Branches penetrating the anterior epithelial cell layer could not be visualized. CONCLUSIONS: 3D-CLSM allows analysis of the spatial arrangement of the anterior corneal nerves and visualization of the epithelium and keratocytes in the living human cornea. The developed method provides a basis for further studies of alterations of the cellular arrangement and epithelial innervation in corneal disease. This may help to clarify alterations of nerve fibre patterns under various clinical and experimental conditions.

Adult↗

PubMed2006

In vivo confocal microscopy of the ocular surface.

Over the past two decades, the applications of in vivo confocal microscopy to the investigation of ocular surface diseases in the living eye have been greatly extended. Confocal microscopy enables detailed investigation of tarsal and palpebral conjunctiva, central and peripheral cornea, tear film, and lids, and it allows evaluation of the ocular surface at the cellular level. High-quality imaging in both contact and noncontact modes has allowed new understanding of the functions of the ocular surface system, and in the coming years, such knowledge will become increasingly comprehensive and specific. Confocal microscopy may provide a link between well-established ex vivo histology and in vivo study of ocular pathology, not only in clinical science but also in clinical practice. The purpose of this review is to summarize the current knowledge about in vivo confocal microscopy of the ocular surface.

Conjunctiva↗

PubMed2006

Pharmacological-induced haptic changes and the accommodative performance in patients with the AT-45 accommodative IOL.

PURPOSE: To investigate the accommodative performance of the AT-45 (eyeonics Inc, Aliso Viejo, Calif) using three-dimensional ultrasound biomicroscopy. METHODS: The AT-45 haptic region was visualized in vivo 1 month after surgery in four patients using an in-house developed three-dimensional ultrasound biomicroscope. Haptic changes, axial shift, and accommodation amplitude were determined under pharmacologically induced accommodation. RESULTS: The angulation, depending on the accommodation state, could be distinguished and analyzed. In vivo a mean change in haptic angulation of 3.3 +/- 3.3 degrees (range: 0 degrees to 7 degrees) and a mean forward shift of 0.13 +/- 0.08 mm (range: 0.05 to 0.2 mm) were observed for the AT-45 using pharmacologically induced accommodation. A mean accommodative amplitude of 0.44 +/- 0.24 diopters (D) (range: 0.25 to 0.75 D) was found using a Hartinger coincidence refractometer. CONCLUSIONS: Minimal angulation changes and axial movements of the AT-45 have been demonstrated using pharmacological stimulation and objective measurement methods. The mechanical performance of the AT-45 in these eyes does not appear to provide the range of accommodation necessary for close work.

Accommodation, Ocular↗

PubMed2005

Three-dimensional ultrasound biomicroscopy, environmental and conventional scanning electron microscopy investigations of the human zonula ciliaris for numerical modelling of accommodation.

PURPOSE: Biomechanical modelling of the accommodation process is a useful tool for studying the mechanism of accommodation and presbyopia and can aid in the development of accommodative lens-replacing materials. Existing biomechanical models, however, use a very simplified zonula structure. The aim of this study was to use three-dimensional ultrasonic imaging and scanning electron microscopy to provide a more detailed, three-dimensional description of the structure of the human zonula to improve the modelling of accommodation. METHODS: Five human eyes were examined without invasive manipulation using a custom-made three-dimensional ultrasonic imaging technique that allows scanning of features with a spatial resolution of 30 microm. Environmental and conventional scanning electron microscopy (SEM) provided information to complement the ultrasonic images for use in development of a more anatomically correct finite-element model of the zonula structures. These data along with the material properties of the ocular tissue structures were used to construct an advanced geometric model for finite-element simulation of the accommodation process. RESULTS: Images were obtained through three-dimensional ultrabiomicroscopy (3D-UBM) of anatomical features heretofore not directly imagable in their native state. Ciliary processes and zonula structures were clearly separated by both the 3D-UBM and the SEM methods. It was found that fibres inserting on the anterior and posterior lens capsule emerge anteriorly at the ciliary body. Fibres emerging near the pars plana insert on the lens and the ciliary body. No X-shaped crossing fibres were found. Modelling of the accommodation process with both the simple and the more complex geometric models produced refractive power changes comparable with in vivo findings. CONCLUSIONS: The 3D-UBM allowed examination of zonula structures in their native state with minimized preparation artefacts. While these data were incorporated into a complex and more anatomically correct finite-element simulation of intraocular features including lens, zonular system and ciliary body it was found that a simplified zonular model is sufficient for the numerical simulation of the accommodation process.

Accommodation, Ocular↗

PubMed2005

Changes of the accommodative amplitude and the anterior chamber depth after implantation of an accommodative intraocular lens.

BACKGROUND: Modern cataract surgery is interested in recovery of the accommodative power. This investigation aimed at determining pseudophakic accommodation in subjects implanted with the accommodative Human Optics 1 CU intraocular lens after drug-induced ciliary muscle stimulation by measuring the objective refraction and the changes in anterior chamber depth in comparison with a PMMA intraocular lens with rigid haptics. METHODS: The studied sample involved 30 eyes of 30 patients undergoing cataract surgery due to age-related cataract. Patients were between 50 and 77 years of age (67.71 +/- 8.0). No randomization was performed. The 1 CU accommodative intraocular lens and the PMMA intraocular lens were implanted in 15 eyes of patients with an expected visual acuity of at least 0.7. Objective refraction under pilocarpine-stimulated ciliary muscle contraction was determined with a Hartinger coincidence refractometer. The anterior chamber depth was measured with Jäger's Haag-Streit slit-lamp attachment. The accommodative amplitude and the anterior chamber flattening were calculated from the measured values. RESULTS: Twelve weeks after surgery the average accommodative amplitude in eyes with a 1 CU intraocular lens calculated from the refractive change under drug-induced stimulation was 0.48 +/- 0.36 D (with a maximum of 1.25 D). The measured change of anterior chamber depth under drug-induced stimulation was 0.3 +/- 0.32 mm (at a maximum of 0.9 mm). In the reference group with PMMA lenses, the mean accommodative amplitude derived from the refractive changes under drug-induced stimulation was 0.34 +/- 0.27 D (at a maximum of 0.85 D). The measured change in anterior chamber depth under drug-induced stimulation was 0.18 +/- 0.09 mm (at a maximum of 0.31 mm). No statistically significant differences were found between the two groups of lenses concerning change in anterior chamber depth and accommodative amplitude. CONCLUSIONS: This investigations indicate a mean anterior 1 CU shift of only 0.32 mm and a maximum of 0.9 mm. The accommodative amplitudes measured with the Hartinger coincidence refractometer (mean value 0.47 D) correspond to these values. Similar conclusions may be drawn from existing investigative results of the reference group, which are on the same order of magnitude as those of the 1 CU group. Objective accommodation measurements are needed to evaluate commercially available accommodative intraocular lenses in a scientifically satisfactory manner. Objectively measurable parameters include changes of the anterior chamber depth as well as refraction, as determined for instance by coincidence refractometry and streak retinoscopy. Future studies should also consider the IOL properties, astigmatism, and pupillary diameter. This is the only way to identify pseudoaccommodation and a decisive factor for further development of accommodative artificial lenses.

Accommodation, Ocular↗

PubMed2002

Monitoring accommodative ciliary muscle function using three-dimensional ultrasound.

BACKGROUND: Our objective was to develop a three-dimensional high-resolution ultrasonic imaging technique to be utilized for in-vivo characterization of the ciliary body and the posterior iris. The benefit of this imaging in enhancing the quantification of the configurational changes in the ciliary body during accommodation is demonstrated. METHODS: Sequential ultrasound biomicroscopic images of the ciliary body region were obtained with a computer-controlled scanning device designed for use with a standard ultrasound biomicroscope for 3D imaging. Custom-made software allows online data collection, data analysis and 3D reconstruction in conjunction with commercially available VoxelView software. RESULTS: The three-dimensional presentation allows a close approximation of the ciliary muscle inside the ciliary body in vivo. We are able to distinguish and to analyze the changes in the muscle contour in different accommodation states. During accommodation a shift in the ciliary muscle center of gravity in a range of 0.04-0.26 mm (mean 0.13+/-0.06 mm) in the direction of the lens equator, with an interindividual variation and a small decrease with age, was observed. CONCLUSIONS: High-resolution ultrasound is a well established technique for in-vivo investigation of the anterior segment. Three-dimensional ultrasound biomicroscopy allows an assessment of the individual ciliary muscle activity in consideration of the ciliary processes. In combination with a contour analysis tool we improved the muscle contour determination during different accommodation states. The investigation showed an activity of the ciliary muscle in young volunteers as well as those of presbyopic age.

Accommodation, Ocular↗

PubMedDate not supplied

Potentially accommodating intraocular lenses--an in vitro and in vivo study using three-dimensional high-frequency ultrasound.

PURPOSE: To investigate the accommodative performance of new intraocular lenses (IOL) using the advantages of three-dimensional ultrasound biomicroscopy. METHODS: An in vitro simulation device was designed to study IOL performance using an artificial capsular bag and a stretching device. The haptic region of the Akkommodative 1CU (HumanOptics AG) and CrystaLens AT-45 (Eyeonics Inc) was visualized in vitro in three dimensions, using an in-house developed three-dimensional ultrasound biomicroscope. The in vitro results were used to describe the in vivo situation in four patients with accommodative implants. RESULTS: The haptic position and angulation in consideration of the accommodation state was distinguished and analyzed. In the simulation model, a maximal angulation change of 4.5 degrees and 4.3 degrees and a maximal forward shift of 0.33 mm and 0.28 mm was observed for the AT-45 and 1CU, respectively. In vivo, a change in haptic angulation <100 and a maximal forward shift of 0.50 mm was observed for the 1CU. These changes correspond to a theoretical approximate value of 0.50 diopters. CONCLUSIONS: The in vitro simulation device examined with three-dimensional ultrasound biomicroscopy provided information on the accommodative performance of these potentially accommodative IOL designs. Using three-dimensional ultrasound biomicroscopy, corresponding changes in haptic angulation during pharmacological-induced accommodation were observed.

Accommodation, Ocular↗