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PubMed2003

Optic disc traction syndrome associated with central retinal vein occlusion.

OBJECTIVE: To describe the association between ischemic central retinal vein occlusion (CRVO) and the development of optic disc (vitreopapillary) traction, as verified by optical coherence tomography (OCT). METHODS: In a prospective, noncomparative, observational patient series, 3 women aged 51 to 64 years developed an ischemic type of CRVO. One patient underwent cannulation of the central retinal vein with injection of a tissue plasminogen activator. In each eye, the contour of the optic nerve head could not be accurately detected because of overlying fibrous tissue. Each patient underwent OCT examination 6 to 10 months (average, 8.3 months) after the occlusive event. RESULTS: Optic disc traction was found by OCT in the 3 patients. In each, the disc was elevated, associated with either incomplete posterior vitreous detachment (2 eyes) or vitreopapillary fibrous membrane (1 eye). Secondary peripapillary retinal traction and macular or retinal detachment developed ("optic disc traction syndrome"). These findings were less marked, or not evident, on both clinical examination and ocular ultrasonography. CONCLUSIONS: Optic disc traction and secondary localized retinal detachment can develop after ischemic CRVO and may contribute to the poor visual acuity. This syndrome should merit special attention before surgery for CRVO is planned. The use of OCT was helpful to diagnose this syndrome.

Diagnostic Imaging↗
PubMed2004

Optical coherence tomography findings in myopic traction maculopathy.

OBJECTIVE: To describe the features and incidence of epiretinal traction and related retinal damage in degenerative myopia. DESIGN: Consecutive observational case series. METHODS: We retrospectively reviewed medical records and optical coherence tomography findings of 218 eyes with high myopia of 121 consecutive patients to detect the incidence and features of epiretinal traction-related macular damage. The degree of myopia ranged from -8 to -26 spherical equivalent (mean +/- SD, -16.93 +/- 5.74). Mean +/- SD axial length was 29.75 +/- 2.12 mm. Excluding eyes with possibly confounding features, 125 eyes were analyzed. MAIN OUTCOME MEASURE: Detection of epiretinal traction and related macular damage. RESULTS: Epiretinal traction was found in 58 (46.4%) of 125 eyes and retinal damage, in 43 eyes (34.4%). Macular retinoschisis was the most frequent form of macular damage (25 eyes [58%]), followed by retinal thickening, lamellar hole, and shallow retinal detachment. CONCLUSIONS: Epiretinal traction is a frequent finding in degenerative myopia and, particularly if associated with the presence of staphyloma, can generate a form of macular damage unique to eyes with high myopia. This damage can affect up to one third of these eyes and should be considered as a separate cause of visual loss easily detected by optical coherence tomography at its early stages.

Adult↗
PubMed2002

Micropatterning tractional forces in living cells.

Here we describe a method for quantifying traction in cells that are physically constrained within micron-sized adhesive islands of defined shape and size on the surface of flexible polyacrylamide gels that contain fluorescent microbeads (0.2-microm diameter). Smooth muscle cells were plated onto square (50 x 50 microm) or circular (25- or 50-microm diameter) adhesive islands that were created on the surface of the gels by applying a collagen coating through microengineered holes in an elastomeric membrane that was later removed. Adherent cells spread to take on the size and shape of the islands and cell tractions were quantitated by mapping displacement fields of the fluorescent microbeads within the gel. Cells on round islands did not exhibit any preferential direction of force application, but they exerted their strongest traction at sites where they formed protrusions. When cells were confined to squares, traction was highest in the corners both in the absence and presence of the contractile agonist, histamine, and cell protrusions were also observed in these regions. Quantitation of the mean traction exerted by cells cultured on the different islands revealed that cell tension increased as cell spreading was promoted. These results provide a mechanical basis for past studies that demonstrated a similar correlation between spreading and growth within various anchorage-dependent cells. This new approach for analyzing the spatial distribution of mechanical forces beneath individual cells that are experimentally constrained to defined sizes and shapes may provide additional insight into the biophysical basis of cell regulation.

Acrylic Resins↗
PubMed1995

Traction forces in locomoting cells.

A means of determining quantitative maps of the tractions exerted by locomoting cells on a substratum has been developed. This method is similar to the Harris silicone substratum assay [Harris et al., 1980: Science 208:177-179], but uses an improved non-wrinkling film that deforms more predictably in response to traction forces. The method also utilizes a mathematical analysis of rubber deformation to produce the final map of the distribution of tractions. The resulting maps consistently showed that fish keratocytes exert a steady-state "pinching" on the substratum, perpendicular to the cell's direction of locomotion. No significant rearward tractions were detected at or near the front edge of the cell. Likewise, no significant forward tractions associated with peeling of adhesions were found at the back of the cell. A second assay uses deflection of a lightly attached glass microneedle to measure the total force exerted by locomoting cells. Forces of approximately 4.5 x 10(-3) dyn were required to "stall" locomoting keratocytes. The implications of these findings for cell movement are discussed.

Animals↗
PubMed2004

[Vitreoretinal traction syndrome in multiple sclerosis].

METHODS: From January to December 2001, 89 patients with multiple sclerosis (MS) were treated in our hospital; 24 of them were diagnosed for the first time. All patients underwent a complete ophthalmologic examination including a three-mirror contact lens examination when photopsias were found or the disease was diagnosed primarily. RESULTS: Two patients showed vitreoretinal tractions with signs of periphlebitis before clinical-neurological manifestation of multiple sclerosis. The third patient, in whom the disease had been known for years, showed distinct neovascularizations, vasculitis, and recurrent vitreous hemorrhages. High-dose steroid therapy resulted in stabilization of the retinal situation in one patient, but the tractions remained unchanged. Additional laser coagulation in the second patient achieved stabilization and reduction of the tractions. A pars plana vitrectomy led to stabilization of the retinal proliferation in the third patient. CONCLUSIONS: The vitreoretinal traction syndrome is associated with MS and can precede its clinical-neurological manifestation. The good results after argon laser coagulation and vitreoretinal surgery suggest a vascular pathogenesis of these tractions.

Adult↗
PubMed2006

Traction forces of fibroblasts are regulated by the Rho-dependent kinase but not by the myosin light chain kinase.

Adhesive cells show complex mechanical interactions with the substrate, however the exact mechanism of such interactions, termed traction forces, is still unclear. To address this question we have measured traction forces of fibroblasts treated with agents that affect the myosin II-dependent contractile mechanism. Using the potent myosin II inhibitor blebbistatin, we demonstrate that traction forces are strongly dependent on a functional myosin II heavy chain. Since myosin II is regulated by both the myosin light chain kinase (MLCK) and, directly or indirectly, the Rho-associated kinase (ROCK), we examined the effects of inhibitors against these kinases. Interestingly, inhibition of the myosin light chain kinase had no detectable effect, while inhibition of the Rho-dependent kinase caused strong inhibition of traction forces. Our results indicate that ROCK and MLCK play non-redundant roles in regulating myosin II functions, and that a subset of myosin II, regulated by the Rho small GTPase, may be responsible for the regulation of traction forces in migrating fibroblasts.

Animals↗
PubMed2005

Gaze-evoked amaurosis from vitreopapillary traction.

PURPOSE: We report four patients with gaze-evoked amaurosis attributable to incomplete posterior vitreous detachment and ensuing vitreopapillary traction. We present these cases to illustrate and extend the spectrum of vitreopapillary syndromes and to draw attention to vitreopapillary traction and its expected manifestations in both optic disk appearance and optic nerve and retinal function. DESIGN: This is a retrospective observational case series culled from tertiary neuro-ophthalmology practice. METHODS: Patients were evaluated with direct and indirect ophthalmoscopy, Hruby (precorneal) lens, three-mirror Goldmann contact lens, macular contact lens, formal perimetry, fundus photography, fluorescein angiography, and orbital ultrasound. RESULTS: Four patients with gaze-evoked amaurosis had disk edema associated with a partial posterior vitreous separation. These patients were young and had atypical posterior vitreous detachments characterized by persisting vitreopapillary attachments. CONCLUSIONS: Gaze-evoked amaurosis is a rare visual obscuration precipitated by changes in volitional gaze, usually associated with an underlying orbital mass. We extend its etiologies to implicate the vitreous through traction expressed at the optic disk. In our cases, vitreopapillary traction elevated the nerve head and eye movements precipitated transient visual phosphenes followed by gaze-evoked amaurosis caused by traction transmitted from the vitreous to superficial nerve fibers of the retina and disk.

Adult↗
PubMed2006

Prostaglandin I2 release following mesenteric traction during abdominal surgery is mediated by cyclooxygenase-1.

Our study aimed to determine the role of cyclooxygenase-2 in the release of prostaglandin-(PG)-I2 following mesenteric traction during abdominal surgery. In a prospective double-blind, randomized, placebo-controlled study, 40 patients electively scheduled for non-laparoscopic abdominal surgery, were pretreated with the cyclooxygenase-2 inhibitor parecoxib (n=20) or placebo (n=20). Heart rate, arterial blood pressure, oxygenation ratio and plasma concentrations of the stable PGI2-metabolite 6-keto-PGF1alpha were compared between groups before injection of parecoxib (-40 min), immediately before mesenteric traction (0 min), and 5, 10, and 30 min thereafter. In addition, plasma concentrations of valdecoxib, the active metabolite of the prodrug parecoxib, were determined. Plasma concentrations of 6-keto-PGF1alpha and heart rate increased in both groups after mesenteric traction. There were no significant differences between groups at individual times in heart rate, arterial blood pressure and plasma concentrations of 6-keto-PGF1alpha. Oxygenation ratio decreased after 10 and 30 min following mesenteric traction in the parecoxib group with a significant difference between treatment groups at 10 and 30 min. Plasma concentrations of valdecoxib revealed therapeutic values. Our data indicate that PGI2 release following mesenteric traction is mediated by cyclooxygenase-1.

6-Ketoprostaglandin F1 alpha↗
PubMed2006

Determining substrate displacement and cell traction fields--a new approach.

This paper presents a new approach for the traction force microscopy (TFM) method which determines traction forces exerted by adherent cells on a thin, elastic polyacrylamide gel embedded with fluorescent microbeads. In this enhanced TFM method, a pattern recognition technique is first applied to match the pair of microbead embedded images before and after deformation, which subsequently provides the displacement field of the elastic substrate. Once the displacement field is obtained, the 3-D finite element method (FEM) is used to compute cell traction forces. The new TFM has been applied to determine traction forces of human tendon fibroblasts. Compared to existing TFM methods, the present method has the following advantages: (1) its displacement field obtained is associated with microbead movements; (2) it considers the finite thickness of the thin polyacrylamide gel and is therefore free from the infinite half-space approximation adopted by existing TFM methods; and (3) its computation procedure for determining cell traction forces is fast.

Biomechanical Phenomena↗
PubMed2001

Postsurgical evaluation of idiopathic vitreomacular traction syndrome by optical coherence tomography.

PURPOSE: To report a case of idiopathic vitreomacular traction syndrome with preoperative and postoperative evaluation by optical coherence tomography. DESIGN: Interventional case report. METHODS: A 62-year-old woman presented with blurred vision in the left eye because of idiopathic vitreomacular traction syndrome, and she underwent a pars plana vitrectomy. Optical coherence tomography was performed before and after surgery. RESULTS: Preoperative optical coherence tomography, right eye, revealed residual adhesion of incomplete posterior vitreous detachment and edematous, thickened outer retina in the macula. A successful vitrectomy relieved vitreoretinal traction with nearly complete resolution of cystoid macular edema within 1 month after surgery, followed in subsequent months by gradual foveal depression resembling a lamellar macular hole. Resolution of subretinal serous fluid was delayed with complete disappearance, some 12 months after surgery, which correlated with a gradual improvement in visual acuity. CONCLUSION: Optical coherence tomography provides a sensitive anatomical evaluation of vitreomacular traction syndrome. Reorganization of retinal tissue after surgical intervention for vitreoretinal traction may be slower than is apparent from conventional examinations.

Diagnostic Techniques, Ophthalmological↗
PubMed1998

Flexion and traction effect on C5-C6 foraminal space.

OBJECTIVE: To determine the effects of cervical flexion and traction on foraminal volume and isthmus area at the C5-C6 foraminal space in cadavers. DESIGN: This study evaluated the foraminal space at C5-C6 in cadaver specimens during flexion and traction of the cervical spine. SETTING: An orthopedic biomechanics laboratory and department of radiology of a university medical center. PATIENTS OR OTHER PARTICIPANTS: Nine cadaver cervical spines, C1 through T3, were used in the study. Superficial tissues were dissected, preserving the ligaments. INTERVENTIONS: Proximal and distal portions of the cadaver spines were potted using bone cement. Spines were mounted and imaged with computed tomography in neutral position, 15 degrees of flexion, and maximum flexion with and without 25lbs of axial traction. MAIN OUTCOME MEASURES: The areas and volumes of the foramen were measured and calculated. RESULTS: Flexion alone significantly increased the foraminal volume and isthmus area at C5-C6. Traction resulted in little additional change. CONCLUSIONS: For cervical spines with mild to moderate degenerative changes at C5-C6, cervical flexion with or without traction produces significant increases in foraminal volume and area at the foraminal isthmus.

Cervical Vertebrae↗
PubMed2003

Temporal variations in cell migration and traction during fibroblast-mediated gel compaction.

Current models used in our laboratory to assess the migration and traction of a population of cells within biopolymer gels are extended to investigate temporal changes in these parameters during compaction of mechanically constrained gels. The random cell migration coefficient, micro (t) is calculated using a windowing technique by regressing the mean-squared displacement of cells tracked at high magnification in three dimensions with a generalized least squares algorithm for a subset of experimental time intervals, and then shifting the window interval-by-interval until all time points are analyzed. The cell traction parameter, tau(0)(t), is determined by optimizing the solution of our anisotropic biphasic theory to tissue equivalent compaction. The windowing technique captured simulated sinusoidal and step changes in cell migration superposed on a persistent random walk in simulated cell movement. The optimization software captured simulated time dependence of compaction on cell spreading. Employment of these techniques on experimental data using rat dermal fibroblasts (RDFs) and human foreskin fibroblasts (HFFs) demonstrated that these cells exhibit different migration-traction relationships. Rat dermal fibroblast migration was negatively correlated to traction, suggesting migration was not the driving force for compaction with these cells, whereas human foreskin fibroblast migration was positively correlated to traction.

Algorithms↗
PubMed1996

Vitrectomy in eyes with peripheral retinal angioma associated with traction macular detachment.

PURPOSE: Peripheral angiomas have been associated with epiretinal membranes and traction retinal detachment. The authors investigated the timing, results, and complications of vitreous surgery to remove the retinal traction and treat the peripheral vascular tumor. METHODS: The authors reviewed the results of ten eyes that had undergone vitrectomy for macular pucker and/or traction retinal detachment. These eyes had either preoperative or intraoperative treatment of the peripheral tumor. RESULTS: Patients were followed 4 to 95 months. Six eyes had nonfamilial peripheral acquired retinal hemangioma, three had von Hippel angiomas, and one had multiple large peripheral retinal angiomas associated with extensive retinal telangiectasis. Four eyes received cryotherapy and/or laser photocoagulation 2 to 3 months before surgery. In the remaining six eyes, initial treatment to the peripheral angioma was performed at the time of vitreous surgery. At final follow-up, all eyes were attached without retinal traction. Vision improved in all eyes; six (60%) achieved 20/50 or better visual acuity. Complications included recurrent epiretinal membrane (n=3); nonregressed angiomas (n=3); increased nuclear sclerosis (n=2); and retinal detachment (n=1). CONCLUSION: Vitreous surgery, when applied to epiretinal membranes or traction retinal detachments associated with peripheral vascular tumors, has a good chance of improving vision. Treatment of the hemangioma, before or during vitrectomy, usually results in tumor regression.

Adult↗
PubMed2002

Epiretinal pathology of vitreomacular traction syndrome.

AIMS: To investigate the ultrastructure of the vitreoretinal interface in patients with vitreomacular traction syndrome. METHODS: 14 patients with vitreomacular traction syndrome underwent standard pars plana vitrectomy. After induction of posterior vitreous detachment, epiretinal tissue and the inner limiting membrane (ILM) of the retina were removed, and processed for transmission electron microscopy. RESULTS: Ultrastructural analysis revealed two basic patterns of vitreoretinal pathology in eyes with vitreomacular traction syndrome. Seven specimens showed mostly single cells or a cellular monolayer covering closely the vitreal side of the ILM, not resulting in a biomicroscopically detectable epiretinal fibrocellular proliferation. The other seven specimens revealed premacular fibrocellular tissue which was separated from the ILM by a layer of native collagen, resembling the clinical features of idiopathic epiretinal membranes. In both groups of eyes, the myofibroblast was the predominant cell type. Fibrous astrocytes and fibrocytes were less frequent. Retinal pigment epithelial cells and macrophages were absent. Deposits of newly formed collagen were present only adjacent to fibrocellular multilayers. CONCLUSIONS: There are two distinct clinicopathological features of vitreomacular traction syndrome which suggest different forms of epiretinal fibrocellular proliferation: (1) epiretinal membranes interposed in native vitreous collagen and (2) single cells or a cellular monolayer proliferating directly on the ILM. The presence of remnants of the cortical vitreous which remain attached to the ILM following posterior vitreous separation may determine the clinicopathological feature of the disease. The predominance of myofibroblasts may help to explain the high prevalence of cystoid macular oedema and progressive vitreomacular traction characteristic for this disorder.

Aged↗
PubMed1994

Diminished oesophageal traction forces with swallowing in gastro-oesophageal reflux disease and in functional dysphagia.

Relations between primary oesophageal peristaltic amplitude and traction force were studied in 30 normal volunteers, 12 patients with functional dysphagia, and 48 patients with gastro-oesophageal reflux disease, using a new intraluminal strain gauge device. Forces generated by swallowing in the normal oesophagus were 42 (35-60) g (median and interquartile range), a close positive correlation existing between traction force and contractile amplitude for each subject (r = 0.5 (0.38-0.6). Traction force increased with increasing balloon volume from 62 (50-73) g at 2 ml to 86 (70-105) g at 4 ml (p < 0.05), indicating distension related modulation of peristaltic force. Patients with oesophagitis generated lower traction forces on swallowing 30 (20-40) g compared with the normal subjects (p < 0.01), the degree of impairment being greatest in those patients with the most severe mucosal damage. Patients with gastro-oesophageal reflux without endoscopic oesophagitis also showed abnormal forces (32 22-38) g p < 0.01 v controls), which were similar to those patients with mild oesophagitis but were greater than those with severe oesophagitis (p < 0.05). In patients with functional dysphagia, forces were also impaired (28 (10-60) g p < 0.05 v controls) despite normal standard manometry. Our results show that measurement of the traction force generated by primary peristalsis provides information about oesophageal neuromuscular function that is not demonstrable by manometry alone and can be abnormal in patients with oesophageal symptoms in whom standard techniques are normal.

Adolescent↗
PubMed2003

Tractional force generation by human müller cells: growth factor responsiveness and integrin receptor involvement.

PURPOSE: To assess the ability of human Müller cells to generate tractional forces and to determine the role of growth factors and collagen binding integrins in this process. METHODS: Müller cells were isolated from papain-DNase-digested human retina. Cell identity and changes in cell phenotype were confirmed by immunodetection of glial fibrillary acidic protein (GFAP), cellular retinaldehyde-binding protein (CRALBP), vimentin, and alpha-smooth muscle actin (alpha-SMA). Generation of tractional force was assessed with a tissue culture assay involving incubation of cells on three-dimensional collagen gels. The effects of contraction-promoting growth factors were examined by adding these directly to the culture medium. Müller cell expression and the involvement of specific integrin receptors were assessed by immunodetection, RT-PCR, and subunit-specific blocking antibodies. RESULTS: During maintenance in culture, human Müller cells adopted a fibroblast-like phenotype capable of generating tractional forces. Matrix contraction was stimulated in a dose-dependent fashion by insulin-like growth factor I and platelet-derived growth factor. Modest responses were observed with high concentrations of transforming growth factor (TGF)-beta1 and -beta2. Müller cells express all four integrin subunits that comprise the collagen-binding receptors including alpha1, alpha2, alpha3, and beta1. Blocking antibodies against receptor subunits alpha2 and beta1 significantly reduced the overall rate of matrix contraction. Antibodies against the alpha1 subunit were modestly inhibitory, whereas anti-alpha3 was without effect. CONCLUSIONS: Human Müller cells acquire the capacity to generate tractional forces in vitro and the contraction-promoting growth factors insulin-like growth factor (IGF)-I and platelet-derived growth factor (PDGF) are potent stimuli. Generation of tractional force by Müller cells primarily involves integrin receptors containing alpha2 and beta1 subunits.

Actins↗
PubMedDate not supplied

Optical coherence tomography imaging of surgical resolution of bilateral vitreomacular traction syndrome related to incomplete posterior vitreoschisis: a case report.

PURPOSE: To report a case of surgical resolution of bilateral vitreomacular traction syndrome related to incomplete posterior vitreoschisis as documented by optical coherence tomography (Stratus OCT, Carl Zeiss Meditec, Dublin, CA). CASE REPORT: In both eyes of a 72-year-old man with bilateral blurred vision, OCT examination disclosed a relevant increase in mean foveal thickness (right eye = 714 microm; left eye = 757 microm) due to a vitreomacular traction syndrome. At the edges of the most highly elevated area of vitreo-macular traction, OCT scans showed a characteristic splitting of the hyperreflective signal in both eyes, usually identified as posterior vitreous cortex. Both eyes underwent vitrectomy with epiretinal membrane peeling. Postoperative OCT examination showed vitreomacular traction resolution in both eyes with an evident decrease in mean foveal thickness (right eye = 364 microm; left eye = 335 microm). Right visual acuity improved from 20/200 to 20/50; left visual acuity changed from 20/150 to 20/40. CONCLUSIONS: OCT was a useful tool in identifying an unusual case of bilateral vitreomacular traction syndrome linked to incomplete posterior vitreoschisis and following a favorable course after surgical management.

Aged↗
PubMedDate not supplied

Spontaneous separation in idiopathic vitreomacular traction syndrome associated with contralateral full-thickness macular hole.

PURPOSE: Vitreomacular traction syndrome (VMTS) and full-thickness macular hole are two different well-known entities that on follow-up may be subjected to clinical modifications. Precisely, a spontaneous separation of idiopathic VMTS occurred in three eyes of three patients relieving in addition traction of the posterior hyaloid that had led also to a focal macular retinal pigment epithelial detachment (RPE). An association to a full-thickness macular hole was observed in the contralateral eye of one of the patients. METHODS: This is a retrospective study of three patients evaluated with fluorescein angiography and documented with optical coherence tomography using the Stratus (OCT) model 3000, with scans analysis and protocols analysis, measuring the size and shape of vitreomacular adhesions, macular thickness changes before and after the spontaneous separation of the tractional posterior hyaloid adhesion. In addition, the vitreous was evaluated with contact lens slit lamp biomicroscopy and ultrasound. The associated contralateral macular hole in one of the patients was surgically treated. RESULTS: Two of the three eyes with spontaneous separation of the VMTS recovered 20/25 central visual acuity; the other eye maintained the initial 20/50 visual acuity. The treated macular hole recovered 20/100 corrected visual acuity. CONCLUSIONS: Spontaneous separation of posterior hyaloid is a possible outcome during follow-up of idiopathic VMTS that can be well evaluated and documented with OCT while macular fluorescein angiography may be silent in cases like these presently reported. Central vision recovery can be excellent following the spontaneous separation, which releases anterior-posterior traction including on the retinal pigment epithelium and decreases macular thickness as measured with OCT. Therefore, regarding management, the indication for vitrectomy should be delayed awaiting the spontaneous release of vitreomacular traction in 4 to 6 months. The association between idiopathic VMTS in one eye and full-thickness macular hole in the opposite eye of one patient is an important pathophysiologic consideration.

Aged↗