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Vitreopapillary traction as a cause of elevated optic nerve head.

PURPOSE: To identify vitreopapillary tractional forces as a possible cause of optic nerve head elevation. METHODS: Case reports. Two patients aged 64 and 84 years underwent detailed ocular examination and B-scan ultrasonography. RESULTS: Both patients had a unilateral elevated optic nerve head with normal color vision, normal pupillary responses, and full kinetic perimetry. Biomicroscopic and B-scan ultrasonographic evaluation confirmed the presence of vitreopapillary traction. CONCLUSIONS: Vitreopapillary traction can cause unilateral optic nerve head elevation. The posterior hyaloid should be evaluated in patients with optic nerve head elevation.

Aged↗

Rho mediates the shear-enhancement of endothelial cell migration and traction force generation.

The migration of vascular endothelial cells in vivo occurs in a fluid dynamic environment due to blood flow, but the role of hemodynamic forces in cell migration is not yet completely understood. Here we investigated the effect of shear stress, the frictional drag of blood flowing over the cell surface, on the migration speed of individual endothelial cells on fibronectin-coated surfaces, as well as the biochemical and biophysical bases underlying this shear effect. Under static conditions, cell migration speed had a bell-shaped relationship with fibronectin concentration. Shear stress significantly increased the migration speed at all fibronectin concentrations tested and shifted the bell-shaped curve upwards. Shear stress also induced the activation of Rho GTPase and increased the traction force exerted by endothelial cells on the underlying substrate, both at the leading edge and the rear, suggesting that shear stress enhances both the frontal forward-pulling force and tail retraction. The inhibition of a Rho-associated kinase, p160ROCK, decreased the traction force and migration speed under both static and shear conditions and eliminated the shear-enhancement of migration speed. Our results indicate that shear stress enhances the migration speed of endothelial cells by modulating the biophysical force of tractions through the biochemical pathway of Rho-p160ROCK.

Animals↗

Scanning Laser Ophthalmoscopic Microperimetry on Idiopathic Epiretinal Membrane and Vitreomacular Traction Syndrome.

Purpose: To evaluate visual function before and after vitrectomy for idiopathic epiretinal membrane and vitreomacular traction syndrome.Methods: Microperimetry with scanning laser ophthalmoscope (SLO) was performed in 4 eyes with idiopathic epiretinal membrane (IERM) and 2 eyes with vitreomacular traction syndrome (VMTS), before and at least 3 months after vitrectomy.Results: Five eyes had preoperative scotoma, which disappeared postoperatively. In 1 eye, absolute and relative scotomas developed postoperatively over the areas where the retinal surface was vigorously scratched to peel off an overlying membrane, and in another eye new scatomas appeared over a newly formed epiretinal membrane 8 months after vitrectomy.Conclusions: To our knowledge, the present report is the first to describe preoperative absolute scotoma in IERM, VMTS and also iatrogenic absolute scotoma due to retinal scratching. SLO microperimetry is useful for evaluation of visual function before and after vitrectomy for epiretinal membrane and vitreomacular traction syndrome.

Journal Article↗

Vitrectomy for vitreous bleeding and tractional retinal detachment in a case of Evans syndrome.

PURPOSE: To evaluate the effect of vitrectomy to treat Evans syndrome with vitreous bleeding followed by tractional retinal detachment. CASE: Vitrectomy was performed on a 21-year-old man with Evans syndrome who developed tractional retinal detachment in the left eye after experiencing vitreous bleeding and tissue proliferation related to the bleeding. OBSERVATIONS: After the proliferative tissue was removed and tractional retinal detachment corrected, the patient's visual acuity improved from 6/20 to 10/20. A small amount of residual proliferative tissue remained after the vitrectomy. CONCLUSIONS: Vitrectomy may be beneficial in patients with serious vitreous complications induced by hematological diseases such as Evans syndrome.

Adult↗

Vitrectomy for diabetic traction retinal detachment using the multiport illumination system.

OBJECTIVE: To examine the visual and anatomic results of bimanual vitrectomy surgery with the multiport illumination system (MIS) in eyes with advanced diabetic traction retinal detachment. DESIGN: Retrospective, noncomparative interventional case series. PARTICIPANTS: Sixty-seven consecutive eyes in 62 patients having vitrectomy with the MIS. METHODS: During surgery, the vitreous, the posterior hyaloid membrane, and fibrovascular proliferative tissue were removed by using bimanual dissection made possible by the MIS. MAIN OUTCOME MEASURES: Retinal reattachment rate, visual function, and postoperative complications were compared with previously published series of vitrectomy for diabetic traction retinal detachment. RESULTS: With a minimum of 6 months of follow-up, complete retinal reattachment was achieved in 62 eyes (93%), and macular attachment was achieved in all 67 eyes. Vision was stabilized or improved in 51 eyes (72%), and 5/200 vision was achieved in 47 eyes (70%). No unique complications, such as incision-related retinal tears, occurred. CONCLUSION: MIS allows bimanual surgery during vitrectomy for diabetic traction retinal detachment, with good visual and anatomic results.

Adult↗

Vitrectomy for rhegmatogenous or tractional retinal detachment with familial exudative vitreoretinopathy.

OBJECTIVE: To examine the anatomic features and surgical indications of familial exudative vitreoretinopathy (FEVR) complicated with rhegmatogenous or tractional retinal detachment. DESIGN: Retrospective noncomparative case series. PARTICIPANTS: Twenty-eight eyes of 25 patients who had either clinically suspected or fully diagnosed FEVR. Of these, 25 had rhegmatogenous retinal detachment, 2 had tractional retinal detachment, and 1 had tractional retinal detachment plus vitreous hemorrhage. INTERVENTIONS: The authors carefully observed the vitreoretinal interface during surgery, studied the clinical and anatomic features of FEVR, and then evaluated the surgical results. RESULTS: The vitreoretinal adhesions were so strong in the peripheral avascular area that iatrogenic retinal breaks easily occurred in 22 of 28 eyes. In all cases, the bimanual technique with vitreous scissors and forceps was required to dissect the posterior vitreous membrane from the retinal surface. The retina was reattached in 24 of 28 cases (85.7%), and visual acuity improved in 20 eyes (71.4%). CONCLUSION: Dissection of the vitreous in the peripheral avascular area is very difficult in FEVR, and those patients for whom this procedure was not successfully performed may have a poorer prognosis.

Adolescent↗

Transient peroneal nerve palsies from injuries placed in traction splints.

Two patients thought to have distal femur fractures presented to the emergency department (ED) of a level 1 trauma center with traction splints applied to their lower extremities. Both patients had varying degrees of peroneal nerve palsies. Neither patient sustained a fracture, but both had a lateral collateral ligament injury and one an associated anterior cruciate ligament tear. One patient had a sensory and motor block, while the other had loss of sensation on the dorsum of his foot. After removal of the traction splint both regained peroneal nerve function within 6 hours. Although assessment of ligamentous knee injuries are not a priority in the trauma setting, clinicians should be aware of this possible complication in a patient with a lateral soft tissue injury to the knee who is placed in a traction splint that is not indicated for immobilization of this type of injury.

Adult↗

Traction forces of cytokinesis measured with optically modified elastic substrata.

Animal cells dividing in culture undergo a dramatic sequence of morphological changes, characterized by cytoskeletal disassembly as cells round up, redistribution of actin, myosins and other cytoplasmic and surface molecules into the cleavage furrow, and respreading, before daughter cells finally separate at the mid-body. Knowledge of forces governing these movements is critical to understanding their mechanisms, including whether formation of the cleavage furrow results from increased force generation at the equator or relaxation at the poles, and whether traction force subsequently mediates cytofission of the intercellular bridge. We have quantitatively mapped traction forces in dividing cells, by extending the silicone-rubber substratum method to detect forces of nanonewtons to micronewtons. We used a new silicone polymer to fabricate substrata whose compliance can be adjusted precisely by ultraviolet irradiation. We show that traction force appears locally at the furrow in the absence of relaxation at the poles during cleavage. Force also rises as connected daughter cells respread and attempt to separate, suggesting that tension contributes to the severing of the intercellular bridge when cytokinesis is completed.

3T3 Cells↗

Ultrastructure of vitreomacular traction syndrome associated with persistent hyaloid artery.

AIM: To demonstrate the ultrastructure of vitreomacular traction associated with persistent hyaloid artery. METHODS: Pars plana vitrectomy was performed in a 66-year-old man with progressive vitreomacular traction associated with a persistent hyaloid artery. Epimacular tissue was peeled and processed for transmission electron microscopy. RESULTS: Ultrastructural analysis revealed multiple sheets of cellular and collagenous components. Myofibroblasts and newly formed collagen were the predominant features. Fibrous astrocytes, fibroblasts, macrophages, and basement membrane were also present. CONCLUSION: The cellular composition of the epimacular tissue and high cellular activity suggest that persistence of the hyaloid artery may contribute to the development of vitreomacular traction.

Aged↗

[Vitrectomy for vitreo-macular traction syndrome].

BACKGROUND: In vitreomacular traction syndrome (VTS), partial posterior vitreous detachment is combined with persistent macular adherence of the vitreous cortex, inducing macular traction changes and functional disturbances. The purpose of our study was to evaluate the anatomical and functional results of vitrectomy for clinically active VTS. PATIENTS AND METHODS: We retrospectively reviewed 38 consecutive eyes from 36 patients (average age 71.4 years) that underwent pars plana vitrectomy for symptomatic VTS. Vitrectomy was combined with epiretinal membrane peeling in 32 eyes and internal limiting membrane peeling in 14 eyes. RESULTS: Mean postoperative follow-up period was 22.4 months. Cystoid macular edema (CME), which was identified preoperatively on biomicroscopic examination and fluorescein angiography in 30 cases, disappeared in all cases but three (92 %). Visual acuity (VA) improved in 26 eyes (68 %), with 12 eyes (32 %) gaining 4 lines or more. Mean VA at the end of the follow-up (0.51 +/- 0.08) significantly increased compared to the preoperative one (0.32 +/- 0.06) (p = 0.0002). Intraoperative complications were small petechias (32 %) and retinal tears (8 %), and postoperative complications included progression of nuclear sclerosis (83 %), retinal pigment epitheliopathy (26 %) and retinal detachment (8 %). Two recurrences of epiretinal membrane were observed (5 %). CONCLUSIONS: Vitrectomy is effective in releasing vitreomacular traction, restoring macular anatomy and inducing a regression of CME. Visual acuity improves significantly in most cases.

Adult↗

The traction reaction in infancy-clinical and electromyographic study of normal infants.

The traction reaction was studied in 23 normal infants on 45 occasions at ages ranging from 2 weeks to 12 months. The distribution of the developmental phases of the reaction to some extent differed from that expected from age according to the description of Vojta (1976). EMG recordings from 15 trunk and leg muscles were obtained on 37 occasions from 20 of the infants. Six types of EMG activation pattern during traction were observed in different overlapping age periods from 1 month to 12 months. From these patterns, four well separated stages of motor development were distinguished. They were as follows: 1) No EMG activity related to traction. 2) Trunk flexor activation with weak or irregular activation in leg muscles. 3) Reciprocal activation in trunk flexor and extensor muscles combined with strong co-activation of the leg muscles, and 4) Trunk muscles activated as in stage 3, but the coactivation in leg muscles abolished and gradually followed by functionally adequate activation in some of the leg muscles.

Electromyography↗

[Removal of infected entrapped pacemaker electrodes by continuous traction (author's transl)].

To remove an infected pacemaker system in order to control the infection is often difficult when there is extensive connective-tissue fixation of the electrode. Forced manual extraction may lead to severe complications. For this reason, operative removal, in certain circumstances involving cardiotomy under extracorporeal circulation, has been practised. An alternative is continuous traction in which the probe is attached peripherally and by continuous traction removed from its cardiac attachment. Nine patients have been treated successfully by this method. In eight the electrode was removed within 1-10 days without significant complications. In one instance the electrode-catheter tore within the superior vena cava after 18 days of continuous traction; the remaining catheter, about 12 cm long, was removed with a sling catheter.

Aged↗

Airborne concentrations of benzene and mineral spirits (stoddard solvent) during cleaning of a locomotive generator and traction motor.

Mineral spirits (also called Stoddard solvent), a petroleum distillate, is often used as a degreaser or an industrial cleaning agent. Although several studies measured airborne concentrations of mineral spirits in various occupational settings, none have characterized the airborne concentrations of benzene from use of mineral spirits. Recent case reports have suggested that benzene, as a contaminant in mineral spirits, might be responsible for adverse health effects. Because some claims of health effects in the railroad industry have been attributed to potential historical exposures to mineral spirits and little information is available regarding air concentrations in this type of occupational setting, a simulation study was conducted to quantitate historical exposures a railroad worker might have experienced while spraying mineral spirits on locomotive engine parts in the 1970s. To quantitate potential historical exposures, worker tasks were simulated under worst-case exposure conditions by spraying minerals spirits on a locomotive generator and traction motor. The results of both generator and traction motor cleaning events produced concentrations of mineral spirits ranging from 34 to 221 ppm and an average 1-h concentration of 121 ppm, whereas benzene concentrations associated with the spraying and drying tasks were less than the limit of detection (0.002-0.006 ppm). Results indicate that a railroad worker who cleaned a locomotive traction motor and generator with mineral spirits for 2 h each workday under worst-case exposure conditions would be exposed to an 8-h time-weighted average (based on lapel measurements) of 30.4 ppm airborne mineral spirits. On the basis of the conditions under which these concentrations were obtained, the results should be the reasonable maximum values that can be achieved in a modern-era (post-1970) workplace in the United States.

Air Pollution, Indoor↗

Growth cone behavior and production of traction force.

The growth cone must push its substrate rearward via some traction force in order to propel itself forward. To determine which growth cone behaviors produce traction force, we observed chick sensory growth cones under conditions in which force production was accommodated by movement of obstacles in the environment, namely, neurites of other sensory neurons or glass fibers. The movements of these obstacles occurred via three, different, stereotyped growth cone behaviors: (a) filopodial contractions, (b) smooth rearward movement on the dorsal surface of the growth cone, and (c) interactions with ruffling lamellipodia. More than 70% of the obstacle movements were caused by filopodial contractions in which the obstacle attached at the extreme distal end of a filopodium and moved only as the filopodium changed its extension. Filopodial contractions were characterized by frequent changes of obstacle velocity and direction. Contraction of a single filopodium is estimated to exert 50-90 microdyn of force, which can account for the pull exerted by chick sensory growth cones. Importantly, all five cases of growth cones growing over the top of obstacle neurites (i.e., geometry that mimics the usual growth cone/substrate interaction), were of the filopodial contraction type. Some 25% of obstacle movements occurred by a smooth backward movement along the top surface of growth cones. Both the appearance and rate of movements were similar to that reported for retrograde flow of cortical actin near the dorsal growth cone surface. Although these retrograde flow movements also exerted enough force to account for growth cone pulling, we did not observe such movements on ventral growth cone surfaces. Occasionally obstacles were moved by interaction with ruffling lamellipodia. However, we obtained no evidence for attachment of the obstacles to ruffling lamellipodia or for directed obstacle movements by this mechanism. These data suggest that chick sensory growth cones move forward by contractile activity of filopodia, i.e., isometric contraction on a rigid substrate. Our data argue against retrograde flow of actin producing traction force.

Animals↗

Traction avulsion amputation of the major upper limb: a proposed new classification, guidelines for acute management, and strategies for secondary reconstruction.

Major replantation of a traction avulsion amputation is undertaken with the goal of not only the reestablishment of circulation, but also functional outcome. This type of amputation is characterized by different levels of soft-tissue divisions involving crushing, traction, and avulsion injuries to various structures. Between 1985 and 1998, 27 cases were referred for secondary reconstruction following amputation of the upper extremity involving both arm and forearm. Replantation was performed by at least 12 qualified plastic surgeons using different approaches and management, resulting in different outcomes. Initial replantation management significantly affects the later reconstruction. For comparing studies and prognostic implications, the authors propose a new classification according to the level of injury to muscles and innervated nerves: type I, amputation at or close to the musculotendinous aponeurosis with muscles remaining essentially intact; type II, amputation within the muscle bellies but with the proximal muscles still innervated; type III, amputation involving the motor nerve or neuromuscular junction, thereby causing total loss of muscle function; and type IV, amputation through the joint; i.e., disarticulation of the elbow or shoulder joint. Some patients required further reconstruction for functional restoration after replantation, but some did not. Through this retrospective study based on the proposed classification system, prospective guidelines for the management of different types of traction avulsion amputation are provided, including the value of replantation, length of bone shortening, primary or delayed muscle or nerve repair, necessity of fasciotomy, timing for using free tissue transfer for wound coverage, and the role of functioning free muscle transplantation for late reconstruction. The final functional outcome can also be anticipated prospectively through this classification system.

Adolescent↗

Idiopathic progressive unilateral vitreous fibrosis and secondary traction retinal detachment.

Two eyes with idiopathic progressive avascular fibrocellular proliferation involving the posterior vitreous surface and causing visual loss due to traction on the optic nervehead, peripapillary retina, and macula were studied. This occurred in one eye of each of two elderly patients. There were no other apparent abnormalities. Vitreous surgery was used to remove the posterior vitreous surface and most of the abnormal tissue. This reduced the traction on the retina, although partial visual loss persisted because of chronic macular edema in each case. Ultrastructural examination of the excised tissue confirmed the fibrocellular nature of the membranes. New-formed collagen was identified in one case, indicating collagen synthesis by the cellular elements. The cells were identified as fibrocytes and myofibrocytes. The latter cells contained cytoplasmic microfilaments thought to be contractile protein, and contraction of the cells was thought to account for the vitreoretinal traction observed clinically. The origin of these cells could not be established by ultrastructural criteria, although clinical features suggest that cells (possibly fibrous astrocytes) from the optic nervehead were responsible for the cellular proliferation.

Aged↗

Posterior tractional retinal breaks complicating branch retinal vein occlusion.

A total of 358 patients with branch retinal vein occlusion (BRVO) were reviewed to examine the relationship between branch retinal vein occlusion with neovascularization elsewhere (NVE), vitreous hemorrhage, and posterior tractional retinal breaks. Twenty-eight of 358 (7.8%) BRVO patients had vitreous hemorrhage. In this group of 28 patients, 24 of the 28 (85.7%) had NVE. Of the 24 BRVO patients with vitreous hemorrhage and NVE, six (21.4%) were found to have posterior tractional retinal breaks adjacent to avulsed neovascular tissue. These data indicate a strong association between BRVO patients with vitreous hemorrhage and posterior tractional retinal breaks due to avulsion of neovascular tissue.

Aged↗

Vitrectomy update for macular traction in ocular toxocariasis.

PURPOSE: To study the results of modern vitrectomy in traction and combined traction-rhegmatogenous retinal detachment involving the macula in cases of ocular toxocariasis. METHODS: This was a cohort study of patients seen in different institutions in the United States. Ten eyes of 10 patients were studied. Vitrectomy was performed in all eyes, combined with membrane removal, scleral buckle, fluid-gas exchange, silicone oil, or lensectomy in certain cases. The anatomic and visual results of surgery were reviewed. RESULTS: Ten eyes from 10 patients ranging in age from 2 to 33 years (median, 6 years) were reviewed. Follow-up ranged from 3 months to 8 years (median, 2 years). All eyes achieved macular attachment following surgery; vision improved in 5 (50%) eyes, and was unchanged in 5 (50%). Histologic specimens from six eyes were reviewed, and revealed combinations of fibrous tissue, eosinophils, plasma cells, lymphocytes, and giant cells. One specimen revealed an encysted Toxocara canis organism. CONCLUSION: Inflammation created in response to Toxocara larvae may lead to traction retinal detachment of the macula. Vitreoretinal surgery has a good chance of reattaching the macula and improving vision.

Adolescent↗