Morphometric analyses of the visual pathways in macular degeneration

Introduction. Macular degeneration (MD) causes central visual field loss. When field defects occur in both eyes and overlap, parts of the visual pathways are no longer stimulated. Previous reports have shown that this affects the grey matter of the primary visual cortex, but possible effects on the preceding visual pathway structures have not been fully established. Method. In this multicentre study, we used high-resolution anatomical magnetic resonance imaging and voxel-based morphometry to investigate the visual pathway structures up to the primary visual cortex of patients with age-related macular degeneration (AMD) and juvenile macular degeneration (JMD). Results. Compared to age-matched healthy controls, in patients with JMD we found volumetric reductions in the optic nerves, the chiasm, the lateral geniculate bodies, the optic radiations and the visual cortex. In patients with AMD we found volumetric reductions in the lateral geniculate bodies, the optic radiations and the visual cortex. An unexpected finding was that AMD, but not JMD, was associated with a reduction in frontal white matter volume. Conclusion. MD is associated with degeneration of structures along the visual pathways. A reduction in frontal white matter volume only present in the AMD patients may constitute a neural correlate of previously reported association between AMD and mild cognitive impairment. Keywords: macular degeneration - visual pathway - visual field - voxel-based morphometryComment: appears in Cortex (2013

Automated Morphometry of the Visual Pathway in Primary Open-Angle Glaucoma

PURPOSE. To establish whether primary open-angle glaucoma (POAG) is associated with a change in volume of the visual pathway structures between the eyes and the visual cortex. METHODS. To answer this question, magnetic resonance imaging (MRI) was used in combination with automated segmentation and voxel-based morphometry (VBM). Eight patients with POAG and 12 age-matched control subjects participated in the study. Only POAG patients with bilateral glaucomatous visual field loss were admitted to the study. The scotoma in both eyes had to include the paracentral region and had to, at least partially, overlap. All participants underwent high-resolution, T(1)-weighted, 3-T MRI scanning[b]. Subsequently, VBM was used to determine the volume of the optic nerves, the optic chiasm, the optic tracts, the lateral geniculate nuclei (LGN), and the optic radiations. Analysis of covariance was used to compare these volumes in the POAG and control groups. The main outcome parameter of the measurement was the volume of visual pathway structures. RESULTS. Compared with the controls, subjects with glaucoma showed reduced volume (P <0.005) of all structures along the visual pathway, including the optic nerves, the optic chiasm, the optic tracts, the LGN, and the optic radiations. CONCLUSIONS. POAG adversely affects structures along the full visual pathway, from the optic nerve to the optic radiation. Moreover, MRI in combination with automated morphometry can be used to aid the detection and assessment of glaucomatous damage in the brain. (Invest Ophthalmol Vis Sci. 2011;52:2758-2766) DOI:10.1167/iovs.10-568

Postoperative Metamorphopsia in Macula-Off Rhegmatogenous Retinal Detachment:Associations with Visual Function, Vision Related Quality of Life, and Optical Coherence Tomography Findings

To evaluate postoperative metamorphopsia in macula-off rhegmatogenous retinal detachment (RRD) and its association with visual function, vision related quality of life, and optical coherence tomography (OCT) findings.45 patients with primary macula-off RRD were included. At 12 months postoperatively, data on metamorphopsia using sine amsler charts (SAC), best corrected visual acuity (BCVA), letter contrast sensitivity, color vision (saturated and desaturated color confusion indexes), critical print size, reading acuity, the 25-item National Eye Institute Visual Functioning Questionnaire (NEI-VFQ-25), and OCT, were obtained.Metamorphopsia was present in 39 patients (88.6%), with most of them (n = 35, 77.8%) showing only mild metamorphopsia (SAC score = 1). Patients with metamorphopsia had significantly worse postoperative BCVA (p = 0.02), critical print size (p<0.0005), and reading acuity (p = 0.001) compared to patients without metamorphopsia. Other visual function outcomes and NEI-VFQ-25 overall composite score were all also somewhat lower in patients with metamorphopsia, but this did not reach statistical significance. No association with OCT findings was present.The prevalence of postoperative metamorphopsia in macula-off RRD patients is high, however, the degree of metamorphopsia is relatively low. When metamorphopsia is present, visual functions seem to be compromised, while vision related quality of life is only mildly affected

Postoperative Vision-Related Quality of Life in Macula-Off Rhegmatogenous Retinal Detachment Patients and Its Relation to Visual Function

To determine the vision-related quality of life (VR-QOL) after surgery for macula-off rhegmatogenous retinal detachment (RRD) in relation to visual acuity, contrast acuity, and color vision.In a prospective observational study, we included 55 patients with a macula-off RRD. Best corrected visual acuity (BCVA), color vision (saturated and desaturated color confusion indices (CCI)) and contrast acuity were measured at 12 months postoperatively in both the RRD eye and the fellow control eye, and the 25-item National Eye Institute Visual Function Questionnaire (NEI VFQ-25) was filled out.Operated and fellow control eyes differed significantly in mean LogMAR BCVA (P<0.0001), median Log contrast acuity (P<0.0001), saturated CCI (P = 0.009), and desaturated CCI (P = 0.016). Significant correlations were observed between the NEI VFQ-25 overall composite score and postoperative LogMAR BCVA (R = -0.551, P<0.0001), contrast acuity (R = 0.472, P<0.0001), saturated CCI (R = -0.315, P = 0.023), and desaturated CCI (R = -0.283, P = 0.044).A lower VR-QOL was highly correlated to a worse postoperative BCVA and contrast acuity and to a lesser extent to color vision disturbances

Enzymatic Breakdown of Type II Collagen in the Human Vitreous

PURPOSE. To investigate whether enzymatic collagen breakdown is an active process in the human vitreous. METHODS. Human donor eyes were used for immunohistochemistry to detect the possible presence of the matrix metalloproteinase (MMP)-induced type II collagen breakdown product col2-3/4C-short in the vitreous. Western blot and slot blot analyses were used to further identify vitreal type II collagen breakdown products in three age groups with average ages of 25, 45, and 65 years. Purified type II collagen was cleaved by MMPs that are known to occur naturally in the vitreous to elucidate what possible type II collagen breakdown products could thus be formed in the human vitreous. RESULTS. By means of both immunohistochemistry and slot blot analysis, col2-3/4C-short was detected in the vitreous. Using Western blot analysis, a range of type II collagen breakdown products was found, mostly in younger eyes, but none of these products contained the neoepitope that characterizes the col23/4C-short molecule. Digestion of purified type II collagen by MMPs did not give the same breakdown products as found in the vitreous. CONCLUSIONS. The presence of collagen degradation products in the human vitreous supports the hypothesis that enzymatic breakdown is most likely an active process in this extracellular matrix. Based on the size of the degradation products found by Western blot analysis, it is likely that in addition to MMPs, other proteolytic enzymes able to digest type II collagen are also active. (Invest Ophthalmol Vis Sci. 2009; 50: 4552-4560) DOI:10.1167/iovs.08-312

Physico-chemistry of bacterial transmission versus adhesion

Bacterial adhesion is a main problem in many biomedical, domestic, natural and industrial environments and forms the onset of the formation of a biofilm, in which adhering bacteria grow into a multi-layered film while embedding themselves in a matrix of extracellular polymeric substances. It is usually assumed that bacterial adhesion occurs from air or by convective-diffusion from a liquid suspension, but often bacteria adhere by transmission from a bacterially contaminated donor to a receiver surface. Therewith bacterial transmission is mechanistically different from adhesion, as it involves bacterial detachment from a donor surface followed by adhesion to a receiver one. Transmission is further complicated when the donor surface is not covered with a single layer of adhering bacteria but with a multi-layered biofilm, in which case bacteria can be transmitted either by interfacial failure at the biofilm-donor surface or through cohesive failure in the biofilm. Transmission through cohesive failure in a biofilm is more common than interfacial failure. The aim of this review is to oppose surface thermodynamics and adhesion force analyses, as can both be applied towards bacterial adhesion, with their appropriate extensions towards transmission. Opposition of surface thermodynamics and adhesion force analyses, will allow to distinguish between transmission of bacteria from a donor covered with a (sub)monolayer of adhering bacteria or a multi layered biofilm. Contact angle measurements required for surface thermodynamic analyses of transmission are of an entirely different nature than analyses of adhesion forces, usually measured through atomic force microscopy. Nevertheless, transmission probabilities based on Weibull analyses of adhesion forces between bacteria and donor and receiver surfaces, correspond with the surface thermodynamic preferences of bacteria for either the donor or receiver surface. Surfaces with low adhesion forces such as polymer-brush coated or nanostructured surfaces are thus preferable for use as non-adhesive receiver surfaces, but at the same time should be avoided for use as a donor surface. Since bacterial transmission occurs under a contact pressure between two surfaces, followed by their separation under tensile or shear pressure and ultimately detachment, this will affect biofilm structure. During the compression phase of transmission, biofilms are compacted into a more dense film. After transmission, and depending on the ability of the bacterial strain involved to produce extracellular polymeric substances, biofilm left-behind on a donor or transmitted to a receiver surface will relax to its original, pre-transmission structure owing to the viscoelasticity of the extracellular polymeric substances matrix, when present. Apart from mechanistic differences between bacterial adhesion and transmission, the low numbers of bacteria generally transmitted require careful selection of suitably sensitive enumeration methods, for which culturing and optical coherence tomography are suggested. Opposing adhesion and transmission as done in this review, not only yields a better understanding of bacterial transmission, but may stimulate researchers to more carefully consider whether an adhesion or transmission model is most appropriate in the specific area of application aimed for, rather than routinely relying on adhesion models

Influence of wear and overwear on surface properties of etafilcon A contact lenses and adhesion of Pseudomonas aeruginosa

PURPOSE. To determine changes in physicochemical surface properties of contact tenses (CLs) during daily wear and effects of lens wear on adhesion of a Pseudomonas aeruginosa strain from a patient with CL-related keratitis.METHODS. Ten new CL wearers used ionic, etafilcon A lenses with 58% water on both eyes for approximately 10 hours each day during 10 and 50 days. All lenses were treated daily with an appropriate lens care solution. After the CLs were worn for 10 days (first pair of lenses) and 50 days (second pair, representing overwear), hydrophobicity by water contact angles, surface roughness by atomic force microscope, elemental surface composition by x-ray photoelectron spectroscopy (XPS), and adsorbed proteins by SDS-PAGE were determined on one lens. The lens from the contralateral eye was placed in a parallel plate flow chamber for bacterial adhesion after each time interval.RESULTS. Water contact angles on lenses changed from 45degrees on unused lenses to 61degrees +/- 25degrees after 10 days of wear and changed significantly (P &lt;0.05) to 27degrees +/- 14degrees after 50 days of wear. Surface roughness increased significantly (P &lt;0.05) from 4 +/- 2 nm (unused) to 10 +/- 7 nm after 50 days of wear. These changes were accompanied by adsorption of proteinaceous material, as evidenced by XPS and SDS-PAGE, demonstrating adsorption of lysozyme, tear lipocalin, and a 30-kDa protein. Initial bacterial adhesion to worn CLs was lower than to unworn CLs. Furthermore, detachment of adhering bacteria from worn lenses was easier than from unworn lenses. The changes observed in the physicochemical surface properties of the lenses after the CLs were worn for 50 days were accompanied by reports of discomfort by 6 of the 10 new CL wearers. Multiple regression analysis revealed that the most predictive variables for an effect on initial deposition after 10 days of wear were hydrophobicity, roughness, the presence of nitrogen-rich material, including the presence of a 30-kDa protein, and the presence of oxygen-rich material-that is, the type of oxygen adsorbed (O==C or O-C). After 50 days of wear, roughness and the presence of tear lipocalin were most predictive.CONCLUSIONS. This study demonstrates that the physicochemical surface properties changed after wear and overwear, whereas overwear of the lenses decreased initial adhesion of P. aeruginosa #3 under the present experimental conditions.</p

Collagen distribution in the human vitreoretinal interface

PURPOSE. To evaluate the presence of collagen types I to VII, IX, XI, and XVIII at the posterior pole, the equator and the preequatorial area in human donor eyes, since collagens are important macromolecules that contribute to vitreoretinal adhesion at the vitreoretinal interface. METHODS. Freshly isolated human retinectomy samples from the equator were used for reverse transcription-polymerase chain reaction to detect mRNA of the above-mentioned collagens. In addition, human donor eyes and equatorial retinectomy samples were embedded in paraffin, stained with antibodies against the collagens and evaluated by light microscopy (LM). RESULTS. Retinectomy samples expressed mRNA of all tested collagen types. By LM, vitreous cortex was positive for collagen types II, V, IX, and XI. In all three regions within the donor eyes and in the retinectomy samples, the internal limiting membrane (ILM) showed types IV, VI, and XVIII; the retinal vasculature was positive for types I to VI and XVIII in most specimens; and the retinal layers showed condensed spots of type VII. In addition, type VII increased in density and in distribution over the retinal layers toward the posterior pole. CONCLUSIONS. Staining patterns of collagen types I to V, IX, XI, and XVIII confirmed previous observations. Important new findings include the presence of type VI in the ILM and type VII in several layers of the retina. Both collagens can anchor matrix components, and type VI could be involved in vitreoretinal attachment. Furthermore, the presence of collagen mRNA in human retinectomy samples may be an indication of postnatal collagen production by retinal cells

Substrate Elastic Modulus Regulates the Morphology, Focal Adhesions, and alpha-Smooth Muscle Actin Expression of Retinal Muller Cells

PURPOSE. The stiffness of the extracellular matrix has been shown to regulate cell adhesion, migration, and transdifferentiation in fibrotic processes. Retinal Muller cells have been shown to be mechanosensitive; they are involved in fibrotic vitreoretinal diseases. Since fibrosis increases the rigidity of the extracellular matrix, our aim was to develop an in vitro model for studying Muller cell morphology and differentiation state in relation to matrix stiffness. METHODS. A spontaneously immortalized human Muller cell line (MIO-M1) was cultured on type I collagen-coated polyacrylamide gels with Young's moduli ranging from 2 to 92 kPa. Cell surface area, focal adhesion, and the expression and morphology of alpha-smooth muscle actin induced by transforming growth factor beta (TGF-beta [10 ng/mL for 48 hours]) were analyzed by immunocytology. The images were documented by using fluorescence microscopy and confocal scanning laser microscopy. RESULTS. MIO-M1 cells cultured on stiff substrates exhibited a significant increase in cell surface area, stress fiber, and mature focal adhesion formation. Furthermore, Muller cells treated with TGF-beta 1 and TGF-beta 2 and cultured on stiff substrates showed an increased incorporation of alpha-smooth muscle actin into stress fibers when compared to those grown on soft surfaces. CONCLUSIONS. Compliance of the surrounding matrix seems to influence the morphology and contraction of retinal Muller cells in fibrotic conditions. Development of an in vitro model simulating both the normally compliant retinal tissue and the rigid retinal fibrotic tissue helps fill the gap between the results of petri-dish cell culture with rigid surfaces and in vivo findings

Immunohistochemical Evaluation of Idiopathic Epiretinal Membranes and In Vitro Studies on the Effect of TGF-beta on Müller Cells

PURPOSE. The purpose of this study was to investigate the presence of type VI collagen and glial cells in idiopathic epiretinal membrane (iERM) and the role of TGF-beta in the expression of collagens and alpha-smooth muscle actin (alpha-SMA) in retinal Muller cells. METHODS. Idiopathic ERM samples from vitrectomy were analyzed for glial acidic fibrillary protein (GFAP), cellular retinaldehyde-binding protein (CRALBP), alpha-SMA, and type VI collagen using flat-mount immunohistochemistry. To study intracellular collagen expression in relation to cellular phenotype, spontaneously immortalized human Muller cells (MIO-M1) were treated with TGF-beta 1 for 48 hours, and the expression of alpha-SMA and intracellular type I, II, IV, and VI collagens was studied by using immunocytology. Findings in Muller cells were compared with those in fetal lung fibroblasts and newborn skin fibroblasts. RESULTS. A colocalization of GFAP/CRALBP and GFAP/alpha-SMA was found in iERM, indicating a dynamic process of activation of retinal Muller cells in vivo. Transforming growth factor-beta 1 induced up-regulation of alpha-SMA stress fibers in retinal Muller cells and both types of fibroblasts in vitro. The intracellular staining intensity of type I, II, and VI collagens was decreased in retinal Muller cells containing alpha-SMA stress fibers, whereas the intracellular staining intensity of type I and VI collagens in both types of fibroblasts was not affected. CONCLUSIONS. Type VI collagen and activated retinal Muller cells are present in iERM. Transforming growth factor-beta 1 induces an up-regulation of alpha-SMA stress fibers in retinal Muller cells and fibroblasts and appears to have a cell-specific effect on intracellular collagen expression