Removal Of Nucleus Research Articles

AdvanTec Legacy System and the NeoSoniX handpiece.

AdvanTec Legacy System and the NeoSoniX handpiece (Alcon Surgical, Fort Worth, Texas) are improvements to the Legacy System that allow power modulation and customization of surgical technique in phacoemulsification surgery. AdvanTec technology allows power modulation in terms of occlusion power management, global linear flow, mode sequencing, and visco mode. The NeoSoniX handpiece combines sonic oscillations with linear ultrasound to reduce thermal energy during nucleus removal. The AdvanTec System allows lower power, less delivered energy, a lower risk of thermal burns, less chatter, and improved followability during phacoemulsification. These improvements translate into successful clinical outcomes.

Effect of hydrodissection on intraoperative performance: randomized study

Purpose To evaluate the effect of hydrodissection on intraoperative performance during phacoemulsification of age-related nuclear cataracts. Setting Iladevi Cataract & IOL Research Centre, Ahmedabad, India, and Center for Research on Ocular Therapeutics and Biodevices, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA. Methods In a prospective study, 86 eyes were randomly assigned to have multiquadrant hydrodissection (+HD, n = 48) or no hydrodissection (–HD, n = 38) during phacoemulsification of a grade 1 to 3 nuclear cataract. Excluded were patients with grade 4 or 5 nuclear sclerosis, a poorly dilating pupil, or associated ocular/systemic disease. Parameters assessed were nucleus and cortex removal time, the amount of fluid used for cortex removal, and the total amount of fluid used. The ease of nucleus rotation and cortical cleanup was also evaluated and graded subjectively as very easy, difficult, or very difficult. Data were analyzed using the Student t test and the chi-square test. Results The mean nucleus removal time was 355 seconds ± 237 (SD) and 474 ± 212 seconds in the +HD and –HD groups, respectively ( P = .09). The mean cortex removal time was significantly less in the +HD group than in the –HD group (79 ± 51 seconds and 220 ± 222 seconds, respectively) ( P = .007). Significantly less fluid (43%) was used for cortex removal in the +HD group than in the –HD group (mean 70 ± 45 mL and 123 ± 82 mL, respectively) ( P = .013), and significantly less total fluid (35%) was used in the +HD group (312 ± 132 mL and 422 ± 80 mL, respectively) ( P = .002). Nucleus rotation was easy in all eyes in the +HD group; 68.43% of eyes in the –HD group failed to achieve rotation ( P = .001). Cortex removal was very easy in 52.08% of eyes in the +HD group and easy in 47.90%; it was easy in 52.63% in the –HD group, difficult in 36.84%, and very difficult in 10.52%. Conclusion The use of multiquadrant cortical-cleaving hydrodissection made removal of the lens nucleus and cortex easier and faster during phacoemulsification of age-related nuclear cataracts.

Sheep lumbar intervertebral discs as models for human discs

Objective. To determine the water content, collagen content and collagen orientation angle in different regions of sheep lumbar discs. Design. A laboratory study of sheep discs obtained from an abattoir. Methods. A total of 21 sheep lumbar discs were obtained from three lumbar spines. Water content was determined by oven drying (60 °C) to constant mass. Collagen content was determined by hydroxyproline analysis. Fibre orientation angles were determined by X-ray diffraction. Results. Water content increased from 74% of total tissue mass in the outer annulus, to 82% in the inner annulus, to 86% in the nucleus. Collagen content decreased from 30% of total tissue mass in the outer region to 20% in the inner region of the anterior and lateral annulus; it was 16% in the posterior annulus. The orientation angle of the collagen fibres decreased from 59° in the outer region to 56° in the inner region of the anterior and lateral annulus; it was 51° in the posterior annulus. Conclusions. Sheep lumbar intervertebral discs provide a reasonable model for human lumbar intervertebral discs. Relevance Sheep lumbar discs have been used to investigate the effects of removing and replacing the nucleus. These studies indicate that removal of nucleus may lead to further disc degeneration and indicate the material properties required for an implant material. The relevance of these previous studies is increased if human and sheep lumbar discs have a similar composition and structure.

Minimal astigmatism after sutureless planned extracapsular cataract extraction

Purpose To evaluate astigmatism after mini-nuc extracapsular cataract extraction (ECCE) in which a chevron incision is enlarged to 6.0 to 7.0 mm for easier nucleus removal and to compare the results with those using a 5.0 mm incision. Setting Department of Ophthalmology, The Edith Wolfson Medical Center, Sackler Faculty of Medicine, Tel-Aviv University, Holon, Israel. Methods Thirty eyes of 29 patients were enrolled in this study. Keratometry was performed preoperatively and 3 to 9 months postoperatively. The incision length was 6.0 mm in 6 eyes, 6.5 mm in 10 eyes, and 7.0 mm in 14 eyes that had mature cataract. Results The mean induced astigmatism calculated by simple subtraction was 0.12 diopter (D) ± 0.51 (SD), 0.16 ± 0.98 D, and 0.67 ± 0.91 D for the 6.0 mm, 6.5 mm, and 7.0 mm incision, respectively. By vector analysis, the mean induced astigmatism was 0.60 ± 0.30 D, 0.75 ± 0.67 D, and 1.36 ± 0.77 D, respectively. Results by both methods showed no significant difference between the previously reported 5.0 mm incision and the 6.0 mm and 6.5 mm incisions. The 7.0 mm group had statistically significantly greater induced astigmatism than the 5.0 mm group ( P = .01, simple subtraction; P =.002, vector analysis). Conclusions Enlarging the size of the chevron incision up to 7.0 mm resulted in a small increase in induced astigmatism. The enlarged incision simplified the operative technique.

Risk factors for and management of dropped nucleus during phacoemulsification

Purpose: To study the risk factors and management of posteriorly dislocated crystalline lenses during phacoemulsification at a teaching institution. Setting: L.V. Prasad Eye Institute, Hyderabad, India. Methods: This retrospective analysis included all phacoemulsification procedures performed by experienced and inexperienced surgeons over 7 years. The incidence, risk factors for, role of surgical experience, mode of management, and the final outcome of posteriorly dislocated lens nuclei were evaluated. Results: Of a total 11 343 phacoemulsification procedures performed between 1993 and 1999, the nucleus was dropped in 38 eyes (0.3%). Two patients with a dropped nucleus were referred from an outside practice. The incidence of dropped nucleus with experienced surgeons (22/8671; 0.2%) was significantly less than that with inexperienced surgeons (16/2672; 0.6%) ( P = .007). Sixteen of the 22 cases of dropped nucleus (72.7%) in the experienced group and 1 of 16 (6.3%) in the inexperienced group had risk factors ( P = .0005). Nucleus removal was performed using vitreoretinal procedures in 39 eyes; 1 eye with a dropped epinucleus was managed conservatively. The final best corrected visual acuity was 20/40 or better in 21 eyes (53.8%). Conclusions: The incidence of dropped nucleus was more frequent with inexperienced surgeons, even though experienced surgeons had more cases with predisposing risk factors. Modern vitreoretinal procedures reduce morbidity and improve the visual outcome.

Replacing the nucleus pulposus of the intervertebral disc

Objective. To determine whether replacement of the nucleus with a synthetic material would prevent the effects of nucleus removal. Design. Laboratory experiments on excised tissues and a finite element model. Background. Removal of the nucleus from the intervertebral disc causes the inner margins of the annulus to bulge inwards, instead of outwards, during compression. This may cause the annulus to degenerate further. Methods. Video recordings of sheep discs, sectioned in the sagittal plane, were obtained during compression in a materials testing machine; the cut face of the disc was sealed with a Perspex window. Experiments were repeated with the nucleus removed and then replaced by a synthetic implant. A finite element model of an intact disc was also used to investigate the effect of nucleus replacement. Results. When the nucleus of sectioned discs was replaced with the polymer materials, the inward bulging of the annulus was not observed. The predictions from the finite element model of the intact disc were consistent with this result. Conclusions. Replacement of the nucleus with a synthetic material can prevent the changes in annulus behaviour that result from removal of the nucleus. Relevance A suitable implant to replace the nucleus after surgical removal may help prevent inward bulging of the inner layers of the annulus.

Differential regulation of GABA release and neuronal excitability mediated by neuropeptide Y1 and Y2 receptors in rat thalamic neurons.

1. Neuropeptide Y (NPY) produced inhibitory effects on neurons of the thalamic reticular nucleus (RT; n = 18) and adjacent ventral basal complex (VB; n = 22), which included hyperpolarization (approximately 4 mV), a reduction in rebound and regular spikes and an increased membrane conductance. These effects were mediated predominantly via NPY1 receptor activation of G-protein-activated, inwardly rectifying K+ (GIRK) channels. 2. NPY reduced the frequency of spontaneous GABAA receptor-mediated inhibitory postsynaptic currents (sIPSCs) in RT (by 60 +/- 7 %, n = 14) and VB neurons (by 25 +/- 11 %, n = 16), but had no effect on the kinetic properties of sIPSCs. After removal of the RT nucleus, the inhibitory effects of NPY on sIPSCs in VB neurons remained (29 +/- 7 %, n = 5). The synaptic effects were mediated via NPY2 receptors. 3. NPY inhibited the frequency of miniature IPSCs (mIPSCs) in RT and VB neurons (by 63 +/- 7 %, n = 5, and 37 +/- 8 %, n = 10, respectively) in the presence of tetrodotoxin (TTX) (1 microM) but not TTX (1 microM) and Cd2+ (200 microM). 4. NPY inhibited evoked IPSCs in both RT (by 18 +/- 3 %, n = 6) and VB (by 5 +/- 4 %, n = 6) neurons without change in short-term synaptic plasticity. 5. We conclude that NPY1 and NPY2 receptors are functionally segregated in the thalamus: NPY1 receptors are predominantly expressed at the somata and dendrites and directly reduce the excitability of neurons in both the RT and VB nuclei by activating GIRK channels. NPY2 receptors are located at recurrent (RT) and feed-forward GABAergic terminals (VB) and downregulate GABA release via inhibition of Ca2+ influx from voltage-gated Ca2+ channels.

Replacing the nucleus pulposus of the intervertebral disk: prediction of suitable properties of a replacement material using finite element analysis.

An axisymmetric finite element model of a human lumbar disk was developed to investigate the properties required of an implant to replace the nucleus pulposus. In the intact disk, the nucleus was modeled as a fluid, and the annulus as an elastic solid. The Young's modulus of the annulus was determined empirically by matching model predictions to experimental results. The model was checked for sensitivity to the input parameter values and found to give reasonable behavior. The model predicted that removal of the nucleus would change the response of the annulus to compression. This prediction was consistent with experimental results, thus validating the model. Implants to fill the cavity produced by nucleus removal were modeled as elastic solids. The Poisson's ratio was fixed at 0.49, and the Young's modulus was varied from 0.5 to 100 MPa. Two sizes of implant were considered: full size (filling the cavity) and small size (smaller than the cavity). The model predicted that a full size implant would reverse the changes to annulus behavior, but a smaller implant would not. By comparing the stress distribution in the annulus, the ideal Young's modulus was predicted to be approximately 3 MPa. These predictions have implications for current nucleus implant designs.

Silver needle therapy for intractable low-back pain at tender point after removal of nucleus pulposus

Objective: To examine the use of a new silver needle therapy for treating tender points involved in intractable low-back pain after removal of nucleus pulposus.Subjects: The study involved 24 patients (17 men and 7 women) aged 26 to 67 years with a mean age of 54.5 ± 5 years.Settings: The Department of Orthopedics at the First Military Medical University, the Department of Rehabilitation Medicine at the General Hospital of PLA in Beijing, and the Department of Acupuncture, the First People's Hospital in Kunming City, People's Republic of China, were the settings for this study.Methods: The patients were treated with traditional silver needle therapy at tender points in the low back and buttocks. Pain at each of the tender points was measured before and after treatment; the scores were compared with a Student t test.Results: The therapeutic results suggest that the total scores for each tender point after treatment were significantly lower than those taken before treatment (P < .001).Conclusion: Silver needle therapy shows promise for treating low-back pain after surgery for disc herniation. Further clinical trials are needed to confirm the effectiveness of this treatment.

Manual sutureless cataract surgery using a claw vectis

Two-handed sandwich methods of extracapsular cataract extraction using a self-sealing incision have proved difficult for many inexperienced surgeons. We developed a simpler 1-handed technique using a claw vectis—a vectis with a claw placed on its tip. When the nucleus is pulled through the scleral tunnel, it is fixed by the claw and is smoothly removed from a wound of a size comparable to that in the sandwich method. During nucleus removal, viscoelastic material is constantly injected through the irrigation vectis to maintain the anterior chamber depth, resulting in a low incidence of complications. We have performed 620 cases using the technique and found it safe and easy for both novice and experienced surgeons.

Facoemulsificação: resultados e complicações nos primeiros 100 olhos

Purpose: To analyze outcomes and incidence of compli-cations in 100 eyes submitted to phacoemulsification perfor-med by surgeons at the start of their career at the Hospital do Servidor Publico Estadual de Sao Paulo. Methods: The first 100 consecutive cataract operations performed by five surgeons, in patients of the HSPE, using phacoemulsification were evaluated. The surgical technique included a scleral tunnel, continuous curvilinear capsulo-rhexis, nucleus removal by phacoemulsification using a peristaltic pump and intraocular lens implantation, under peribulbar anesthesia. Results: The incidence of complications was 15.2%: posterior capsule tear in 8.7%, vitreous loss in 5.4% and one case of posterior dislocation of the nucleus. Posterior chamber IOL were implanted in 96.7% of the eyes, 70.8% of these being in the capsular bag, 28% in the sulcus and 1.2% were fixed superiorly. The final visual acuity was 20/40 or better in 89% of the cases. None of them developed bullous keratopathy or retinal detachment. Conclusion: The complication rate was comparable to that of the literature, suggesting that this technique may be learned during the residency program.

Phacoemulsification and Modern Cataract Surgery

The techniques and results of cataract surgery have changed dramatically during the past three decades. In the USA, we have moved from intracapsular cataract extraction as the preferred technique to almost exclusively extracapsular techniques. Smaller incisions have become the standard, with phacoemulsification now being the method of choice for most surgeons. Along with these advances have come improved intraocular lens materials and designs, especially well suited for use with smaller incisions. Phacoemulsification as a method to remove the cataractous lens was first proposed more than 20 years ago. Advances in techniques and equipment have led to a dramatic increase in the popularity of phacoemulsification with increased safety and efficiency. Viscoelastic agents have been developed synchronously with modern phacoemulsification techniques, playing an integral role in the success of this new technology. Improved surgical techniques for removing the anterior lens capsule have decreased the incidence of both intraoperative and postoperative capsular complications. Nucleus removal, formerly performed primarily in the anterior chamber, is now performed in the posterior chamber, decreasing damage to the corneal endothelium. Improved wound construction allows many wounds to be left unsutured, and smaller wounds allow shorter recovery time and greater intraoperative control and safety. Intraocular lenses can have smaller optic sizes and still maintain accurate centration. Foldable intraocular lenses can take advantage of the smaller incision, even further shortening the time to visual recovery. Continual evolution of this technology promises to further improve patient outcomes after cataract surgery.

Adhesion to the substratum improves the motility ofAmoeba proteus in the absence of a cell nucleus

Anucleated fragments ofAmoeba proteus obtained by dissection and kept on an untreated glass surface fail to adhere to this substratum, lose motor polarity, and stop moving, at least for several hours. If they are transferred after the operation to a highly adhesive surface (polylysine-coated glass), they adhere to the substratum, although locomotion is not spontaneously restored. However, after exposure to a light-shade difference along their body they start moving towards the shaded area and continue locomotion as long as the photic stimulus is acting. Disorganisation of the F-actin cytoskeleton of anucleated fragments was observed on the untreated glass but reorganization on the polylysine-coated surface. The anucleated fragments can show transient recovery of slight spontaneous motor activity and react promptly to external stimuli after up to several days on untreated glass. These intermittent activity periods are enabled by reconstruction of F-actin cytoskeleton in the anucleated fragments during their temporary adhesion to the glass. It is concluded that the injurious effect of cell nucleus removal on the locomotor capacity of amoebae can be compensated by the simultaneous enhancement of cell adhesion and application of a stimulus restoring the motor polarity of the cell. The compensation is achieved by cytoskeletal reorganization.

Isolation and biochemical mapping in the range of 10 −7 to 10 −12 g of fresh, single mammalian neurons in brain I. Techniques

A free-hand technique to remove single, fresh nerve cells including 50–100 μm of their dendrites, and the removal of its surrounding glia from a defined locus in the mammalian brain is described. Exposition of the neuronal post-synaptic areas, removal of the neuronal nucleus and preparation of a functional plasma membrane are likewise described. Biophysical and biochemical micro methods for determination of macro molecules from 20 pg and of ion fluxes are described. These include UV micro-photometry, micro-electrophoresis (in 20 μm cellulose gel fibers and in 215 or 440 μm gel-filled capillaries), analysis of radiolabeled proteins, and determination of ATPase activity, all applied to single cells or cell fragments.

A Comparison of the Effects of Automated Percutaneous Diskectomy and Conventional Diskectomy on Intradiscal Pressure, Disk Geometry, and Stiffness

Diskectomy, chemonucleolysis, percutaneous diskectomy, and laser ablation are used to treat patients with sciatica. The effects of percutaneous diskectomy on the intradiscal pressure of the human disk are not known. Our aims were to determine (a) whether removal of nucleus through automated percutaneous diskectomy significantly reduces intradiscal pressure without altering the disk geometry and stiffness, and if so, how much nucleus removal is required to achieve these goals; and (b) whether the effects of conventional diskectomy on these same parameters are equivalent to removal of nucleus through automated percutaneous diskectomy. Cyclic compressive loads of 20-900 N were applied to lumbar disks. Conventional diskectomy or automated percutaneous diskectomy (performed for 40 min with biomechanical measurements made four times at 10-min intervals) was then performed under zero load and the specimens retested under the same cyclic compressive loading. There were significant (p < 0.01) decreases in intradiscal pressure (by 7% under 900 N) after 10 min of automated percutaneous lumbar diskectomy. There were no further significant decreases in pressure during the next 30 min of percutaneous diskectomy. There were also significant decreases in pressure due to a puncture hole made with the Nucleotome trephine alone, without removal of disk material, and there was no difference in pressure after trephining alone and after percutaneous diskectomy. Decreases in disk height were significant, ranging from 5% at 10 min to 7% at 40 min of treatment. There were equivalent decreases in intradiscal pressure and disk height due to removal of similar amounts of nucleus during conventional diskectomy and during 40 min of percutaneous diskectomy.(ABSTRACT TRUNCATED AT 250 WORDS)

Nucleus Viscoexpression Compared With Other Techniques of Nucleus Removal in Extracapsular Cataract Extraction With Capsulorhexis

We compared three nucleus delivery procedures used during extracapsular cataract extraction (ECCE) after capsulorhexis in 142 eyes. In 25 eyes, the nucleus was expressed through a capsulorhexis 7 mm or wider. In 40 eyes, the nucleus was broken into two pieces and removed through a capsulorhexis 6 mm or less. In 77 eyes, viscoexpression was used to remove the nucleus from the capsular bag through a capsulorhexis 6 mm or less. Nucleus expression after a wide capsulorhexis was successful in 68% of the eyes in which it was attempted. Nucleus fragmentation was successful in 90%. Postoperative inflammation was high in both of these groups. Nucleus viscoexpression was successful in 93%, with low postoperative inflammation. Although it requires a 7- to 8-millimeter corneoscleral incision, based on our study, viscoexpression would appear to be the best nuclear delivery technique when ECCE, rather than phacoemulsification, is being performed.

Use of a Sheets' Glide as a Pseudoposterior Capsule in Phacoemulsification Complicated by Posterior Capsule Rupture

OBJECTIVE: To determine the safety and efficacy of using a Sheets' glide as a pseudo-posterior capsule to facilitate completion of phacoemulsification of the lens' nucleus following posterior capsule rupture during phaco. STUDY DESIGN: Intra- and postoperative review of Sheets' glide surgical technique used on five adult patients undergoing phacoemulsification who developed a posterior capsule rupture while the nucleus was still in the bag. SETTING: Norwood Clinic, outpatient ophthalmic department, Birmingham, Alabama, USA. MAIN OUTCOME MEASURES: Efficacy of Sheets' glide PC technique in management of this surgical complication. RESULTS: Each patient was successfully treated by manoeuvring the Sheets' glide to occlude the PC posteriorly, thus permitting completion of the removal of residual nucleus by phaco through a 5 to 6 mm scleral incision with an open posterior capsule. CONCLUSION: Although emulsification of the nucleus after PC rupture generally poses significant risk of loss of nuclear debris into the vitreous cavity, insertion of a Sheets' glide between the torn capsule and the nucleus may be safely and effectively used to act as a pseudo-posterior capsule to facilitate completion of the case using phacoemulsification.

Dynamics of human lumbar intervertebral joints. Experimental and finite-element investigations.

To improve our understanding of the dynamic characteristics of the human lumbar spine, both experimental and finite-element methods are required. The experimental methods included measurement of the axial steady state response, resonant frequencies, and damping of seven lumbar motion segments under an upper-body mass of 40 kg. The influence of the presence of posterior elements and different magnitudes of compression preload on the response was also studied. To supplement the measurements, linear and nonlinear, axisymmetric, and three-dimensional finite-element models of a L2-L3 disc-vertebra unit were developed to predict the free and forced-vibration responses. The step and harmonic loadings in the axial direction were considered for the forced-vibration analysis. The effect of the presence of the body mass and compression preloads were also examined. The results of experimental and finite-element studies were in good agreement with each other. They indicated that the system resonant frequencies are reduced considerably with the addition of a body mass of 40 kg and increase significantly (P less than .005) as the compression preload increases. The compliance at both low and resonant frequencies decreases with increasing compression preload. Under preloads of not more than 680 N, removal of the facet joints tends to decrease slightly the segmental resonant frequencies irrespective of the magnitude of compression preload (P less than .1). The finite-element model studies show quasi-static response under harmonic loads with periods much larger than the fundamental period of the segment and under step loads with slow rising times. Under a step load without the body mass, the nucleus pressure varies with both location and time and reaches a maximum of about 2.5 times that under equivalent static load. The addition of a 40-kg mass, in this case, renders a single degree-of-freedom response, with the pressure remaining nearly constant with location inside the nucleus. The stresses and strains throughout the segment in this case increase approximately twofold in comparison with equivalent static values. Partial or complete removal of the disc nucleus considerably decreases the resonant frequency and increases the corresponding segmental response amplitude (ie, compliance). The results indicate that the most vulnerable element under axial vibration loads is the cancellous bone adjacent to the nucleus space. Fatigue fracture of bone as a cumulative trauma and the subsequent loss of nucleus content likely initiates or accelerate the segmental degenerative processes. The annulus fibers do not appear to be vulnerable to rupture when the segment is subjected to pure axial vibration.

Small Pupil IOL Glide

It is not uncommon to perform extracapsular cataract surgery on a patient whose pupil is difficult to dilate, or a pupil that has constricted after anterior capsulotomy, nucleus removal, and prior to IOL implantation. We have designed a simple to use, disposable, IOL glide that would facilitate the introduction of an intraocular lens through a small or poorly dilated pupil. This glide, made of medical grade polyethylene, can atraumatically dilate the pupil and enable lens placement within the capsular bag. In addition the glide, based on the Sheets modification, is universal in that it can be used to implant either anterior or posterior chamber lenses. The glide is particularly useful for facilitating capsular bag implantation of IOLs through pupils of varying diameters.

Lens anatomical principles and their technical implications in cataract surgery Part I: The lens capsule

Optimal fixation and position of an intraocular lens (IOL) is achieved when it is located in the capsular bag. A peripheral tear from the central opening to the lens periphery is associated with a high incidence of dislocation of at least one loop from within the capsular bag and lens decentration. A central round continuous capsulectomy (capsulorhexis), within the zonule-free area, provides long-term and balanced IOL fixation. To perform a well-controlled capsulectomy, a deep and stable anterior chamber should be maintained throughout the surgery. This is achieved by using a continuous anterior chamber maintainer that regulates the pressure in the anterior chamber. This paper reviews the clinical anatomical guidelines of the lens capsule and the anterior chamber and presents the authors' preferred technique for optimal anterior capsulectomy.