Christian Y. Mardin

Bio: Christian Y. Mardin is an academic researcher from University of Erlangen-Nuremberg. The author has contributed to research in topics: Glaucoma & Optic disc. The author has an hindex of 37, co-authored 192 publications receiving 4483 citations. Previous affiliations of Christian Y. Mardin include University of Tübingen & German Cancer Research Center.

Morphometry of the human lamina cribrosa surface.

Abstract: The lamina cribrosa is a sieve-like perforation in the posterior part of the sclera, that allows passage of the retinal ganglion cell axons and central retinal vessels and preserves a pressure gradient between the intraocular and extraocular space. It has been termed the primary site of glaucomatous damage to the optic nerve. Using electron microscopy, the authors morphometrically evaluated the inner surface of the lamina cribosa in 40 normal human donor eyes. There were 14 men and 21 women with a mean age of 52 +/- 22 yr (10-82 yr). Mean single pore area (0.004 +/- 0.001 mm2) and summed pore area were significantly (P less than 0.05) larger and the ratio of summed pore area to lamina area was higher in the inferior and superior regions than in the temporal and nasal regions. The ratio decreased with increasing lamina cribrosa size. Count, size, form, and density of the pores were statistically independent of age, sex, side, and lamina cribrosa form. Pore count and summed pore area (mean: 0.92 +/- 0.22 mm2) increased significantly with enlarging lamina cribrosa size. The area of the lamina cribrosa openings for passage of the central retinal vessels was independent of the lamina cribrosa size. The high ratio of summed pore area to lamina area and the large single pore area may be pathogenetically important for the increased glaucoma susceptibility in the inferior and superior disc regions. The lack of a correlation between lamina cribrosa size and the area of the lamina cribrosa openings for the retinal vessels may explain why central retinal vessel occlusions occur independently of optic disc size.

Retinal nerve fiber layer thickness in normals measured by spectral domain OCT.

Abstract: PurposeTo determine normal values for peripapillary retinal nerve fiber layer thickness (RNFL) measured by spectral domain Optical Coherence Tomography (SOCT) in healthy white adults and to examine the relationship of RNFL with age, gender, and clinical variables.Patients and MethodsThe peripapillar

Common genetic determinants of intraocular pressure and primary open-angle glaucoma

Abstract: Intraocular pressure (IOP) is a highly heritable risk factor for primary open-angle glaucoma and is the only target for current glaucoma therapy. The genetic factors which determine IOP are largely unknown. We performed a genome-wide association study for IOP in 11,972 participants from 4 independent population-based studies in The Netherlands. We replicated our findings in 7,482 participants from 4 additional cohorts from the UK, Australia, Canada, and the Wellcome Trust Case-Control Consortium 2/Blue Mountains Eye Study. IOP was significantly associated with rs11656696, located in GAS7 at 17p13.1 (p = 1.4 x 10(-8)), and with rs7555523, located in TMCO1 at 1q24.1 (p = 1.6 x 10(-8)). In a meta-analysis of 4 case-control studies (total N = 1,432 glaucoma cases), both variants also showed evidence for association with glaucoma (p = 2.4 x 10(-2) for rs11656696 and p = 9.1 x 10(-4) for rs7555523). GAS7 and TMCO1 are highly expressed in the ciliary body and trabecular meshwork as well as in the lamina cribrosa, optic nerve, and retina. Both genes functionally interact with known glaucoma disease genes. These data suggest that we have identified two clinically relevant genes involved in IOP regulation.

Wavelet denoising of multiframe optical coherence tomography data.

Abstract: We introduce a novel speckle noise reduction algorithm for OCT images. Contrary to present approaches, the algorithm does not rely on simple averaging of multiple image frames or denoising on the final averaged image. Instead it uses wavelet decompositions of the single frames for a local noise and structure estimation. Based on this analysis, the wavelet detail coefficients are weighted, averaged and reconstructed. At a signal-to-noise gain at about 100% we observe only a minor sharpness decrease, as measured by a full-width-half-maximum reduction of 10.5%. While a similar signal-to-noise gain would require averaging of 29 frames, we achieve this result using only 8 frames as input to the algorithm. A possible application of the proposed algorithm is preprocessing in retinal structure segmentation algorithms, to allow a better differentiation between real tissue information and unwanted speckle noise.

Unbiased Recursive Partitioning: A Conditional Inference Framework

Abstract: Recursive binary partitioning is a popular tool for regression analysis. Two fundamental problems of exhaustive search procedures usually applied to fit such models have been known for a long time: overfitting and a selection bias towards covariates with many possible splits or missing values. While pruning procedures are able to solve the overfitting problem, the variable selection bias still seriously affects the interpretability of tree-structured regression models. For some special cases unbiased procedures have been suggested, however lacking a common theoretical foundation. We propose a unified framework for recursive partitioning which embeds tree-structured regression models into a well defined theory of conditional inference procedures. Stopping criteria based on multiple test procedures are implemented and it is shown that the predictive performance of the resulting trees is as good as the performance of established exhaustive search procedures. It turns out that the partitions and therefore the...

Sarcoidosis

Abstract: 结节病易误诊,据王洪武等~([1])收集国内18篇关于此病误诊的文献,误诊率高达63.2%,当然有误诊就会有误治,如孙永昌等~([2])报道26例结节病在影像学检查诊断的第一印象中拟诊结核5例,其中就有2例完成规范的抗结核治疗,为此应引起临床对本病诊治的重视。

Optical Coherence Tomography of the Human Retina

Abstract: Objective: To demonstrate optical coherence tomography for high-resolution, noninvasive imaging of the human retina. Optical coherence tomography is a new imaging technique analogous to ultrasound B scan that can provide cross-sectional images of the retina with micrometer-scale resolution. Design: Survey optical coherence tomographic examination of the retina, including the macula and optic nerve head in normal human subjects. Settings Research laboratory. Participants: Convenience sample of normal human subjects. Main Outcome Measures: Correlation of optical coherence retinal tomographs with known normal retinal anatomy. Results: Optical coherence tomographs can discriminate the cross-sectional morphologic features of the fovea and optic disc, the layered structure of the retina, and normal anatomic variations in retinal and retinal nerve fiber layer thicknesses with 10- μm depth resolution. Conclusion: Optical coherence tomography is a potentially useful technique for high depth resolution, cross-sectional examination of the fundus.

Primary open-angle glaucoma.

Abstract: Glaucoma is an optic neuropathy that is characterized by the progressive degeneration of the optic nerve, leading to visual impairment. Glaucoma is the main cause of irreversible blindness worldwide, but typically remains asymptomatic until very severe. Open-angle glaucoma comprises the majority of cases in the United States and western Europe, of which, primary open-angle glaucoma (POAG) is the most common type. By contrast, in China and other Asian countries, angle-closure glaucoma is highly prevalent. These two types of glaucoma are characterized based on the anatomic configuration of the aqueous humour outflow pathway. The pathophysiology of POAG is not well understood, but it is an optic neuropathy that is thought to be associated with intraocular pressure (IOP)-related damage to the optic nerve head and resultant loss of retinal ganglion cells (RGCs). POAG is generally diagnosed during routine eye examination, which includes fundoscopic evaluation and visual field assessment (using perimetry). An increase in IOP, measured by tonometry, is not essential for diagnosis. Management of POAG includes topical drug therapies and surgery to reduce IOP, although new therapies targeting neuroprotection of RGCs and axonal regeneration are under development.