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Biomedical subjects

O Stachs

Publications and source records attributed to O Stachs.

6 recordsLinked to original sources
PubMed2006

[Three-dimensional confocal laser scanning microscopy of the corneal nerve structure].

PURPOSE: The aim of this study was the evaluation of a technology for in vivo visualization of distribution and morphology of corneal nerves by means of 3D confocal laser scanning microscopy (3D-CLSM). METHOD: The anterior corneas of four human volunteers were examined by an in-house developed confocal laser scanning microscope based on a commercially available instrument (Heidelberg Retina Tomograph II, Heidelberg Engineering GmbH, Germany). Raw stacks were converted using ImageJ (NIH, USA) for 3D-reconstruction using AMIRA 3.1 (TGS Inc, USA). RESULTS: The spatial arrangement of epithelium, nerves and keratocytes was visualized by in vivo 3D-CLSM. After 3D-reconstruction of volunteers' corneas, volume rendering and selective oblique sections have been done to demonstrate the nerves in the central human cornea. 3D-imaging shows thick nerve bundles rising out of the deeper stroma. The nerves further divide, resulting in fibers that are arranged parallel to Bowman's layer and are partly interconnected. Branches rising up to the superficial cell layer cannot be visualized. Wound healing following refractive surgery can be evaluated. CONCLUSIONS: 3D-CLSM allows in vivo visualization and analysis of the spatial arrangement of the epithelium, nerves and keratocytes of the human cornea. The developed method provides a basis for further studies on the alterations of the cellular arrangement and epithelial innervation in corneal diseases. This may help to clarify gross variations of nerve fiber patterns under various clinical and experimental conditions.

Adult↗
PubMed2005

Evaluation of biometric methods for measuring the anterior chamber depth in the non-contact mode.

PURPOSE: High-resolution biometry of the anterior ocular segment is now becoming more and more important against a background of refractive surgery and the evaluation of potentially accommodative lens replacement materials. The aim of this study was a systematic investigation of the currently available non-contact methods for measuring the anterior chamber depth (ACD). METHODS: The ACDs of 50 phakic eyes of 27 patients aged between 19 and 59 years were measured with the IOL-Master (Zeiss), the AC-Master (Zeiss), the Pentacam (Oculus) and slit-lamp pachymetry by Jaeger (Haag-Streit). RESULTS: The median anterior chamber depth in the investigated eyes was 3.63 mm for the IOL-Master (minimum 2.88 mm, maximum 4.22 mm), 3.802 mm for the AC-Master (2.816 mm-4.373 mm), 3.915 mm for the Pentacam (minimum 2.994 mm, maximum 4.614 mm) and 3.75 mm for Jaeger (2.887 mm-4.29 mm). With a probability of error of alpha=0.05 there were no significant differences concerning the ACD between the methods of Jaeger and AC-Master, Jaeger and IOL-Master, or Pentacam and AC-Master (Wilcoxon and Wilcox). The intra-individual variability was +/-5.4 microm for AC-Master, +/-12.7 microm for Pentacam, +/-24.5 microm for IOL-Master and +/-41.2 microm for Jaeger. The maximum method-dependent difference in ACD determination was 285 microm. CONCLUSIONS: All the methods allow non-contact biometry, but the results might differ due to measuring principles inherent to the system, experience of the examiner and compliance of the patient. Partial coherence interferometry with the AC-Master offers the advantage of measurement exactly along the optical axis with the highest reproducibility and patient compliance.

Adult↗
PubMed2005

[Three-dimensional ultrasound biomicroscopic examinations for haptic differentiation of potentially accommodative intraocular lenses].

PURPOSE: The principal ability of potentially accommodative IOLs is based on an axial shift of the IOL optics induced by the ciliary body action in interaction with a reversible change in haptic angulation. The aim of this study was to investigate the accommodative performance of this new IOL generation. METHOD: The authors have designed a test device to study IOL performance experimentally. These results were extrapolated to the in vivo situation in patients with accommodative implants. RESULTS: The 3D high-resolution presentation of the anterior segment of the eye allows a separation of the IOL haptic elements. In vitro and in the selected in vivo cases a change in haptic angulation <10 degrees in combination with a maximal IOL shift of 0.5 mm was found. CONCLUSIONS: The simulation model used in combination with 3D ultrasound biomicroscopy provides information about the potential of accommodative IOL designs. Conclusions corresponding to changes in haptic angulation during accommodation can be drawn and applied to the in vivo situation.

Accommodation, Ocular↗
PubMed2004

[The extracellular matrix structure in keratoconus].

PURPOSE: Keratoconus is a non-inflammatory disease characterized by progressive thinning of the central cornea. There are indications for an autosomal dominant heredity. Our purpose was to find correlations between gene expression and structural changes in extracellular matrix components. METHODS: Stromal RNA (keratoconus and comparison) was isolated from corneas, transformed to cRNA and analysed using biochips (Affymetrix). Structural investigations were performed by laser scanning and transmission electron microscopy. RESULTS: In keratoconus corneas there was an upregulation of different extracellular matrix components (collagen XV, metalloproteases) and a down-regulation of collagen IV (alpha1, alpha3) and versican. The morphological changes correlated to genetic obtained data. The orthogonal arrangement of the collagen fibrills (anteriorly and central) was altered in the collagen matrix of keratoconus corneas. CONCLUSIONS: The changes point on deregulation of the matrix arrangement. The interest in the cause of the disease is focused on the interfibrillar arrangement, the interaction between collagen and proteoglucanes.

Adult↗
PubMed2001

Three-dimensional ultrasound findings of the posterior iris region.

PURPOSE: The aim of this study was to assess the benefit of the three-dimensional ultrasound biomicroscopy in examination of the posterior iris and ciliary body. METHODS: Three-dimensional visualisation of the anterior eye section was achieved through extension of the existing ultrasound biomicroscope system (Humphrey Instruments). Visualisation of posterior iris and ciliary body pathologies in three patients was performed with a three-dimensional reconstruction technique of B-scans. RESULTS: The extended ultrasound system provided three-dimensional visualisation of alterations of the posterior iris region, i.e. iris cysts, ciliary body cysts and solid tumours of the ciliary body and iris. CONCLUSIONS: The three-dimensional ultrasound biomicroscopy yields extended diagnostic findings regarding iris and ciliary body pathology. This method offers an improved assessment of the posterior surface of the iris and the volume of the ciliary body. Furthermore, these data can be useful for procedures in computer simulation and calculation for a better understanding of the function of the ciliary body in the accommodation process.

Adult↗