Management, risk factors and treatment outcomes of rhegmatogenous retinal detachment associated with giant retinal tears: scoping review.

BACKGROUND: Rhegmatogenous retinal detachment (RRD) is a serious condition that occurs when the retina detaches from its underlying retinal pigment epithelium. RRDs associated with giant retinal tears (GRTs) are caused by retinal tears at least 90° or one-quarter of the circumferential extent. This scoping review systematically identifies and summarizes clinical studies evaluating surgical techniques for the management of GRT-related RRDs, discusses functional and visual outcomes and the risk factors affecting treatment outcomes. METHODS: This study was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. PubMed, Scopus, Google Scholar, and Springer Link databases were searched for relevant papers (from January 2001 to March 2023). Studies that were published in the English language and reported the risk factors, management, and treatment outcomes of GRT-related RRDs were included in the review. The outcome measures included anatomic success rates, changes in BCVA (logMAR) from baseline to the final follow-up, and adverse events. RESULTS: A total of 11,982 articles were identified. After the title and abstract review, 71 studies were deemed eligible for full-text review. Thirty-six studies that met the eligibility criteria were included in the final review. Four surgical techniques were identified: pars plana vitrectomy (PPV), combined PPV and scleral buckling, scleral buckling alone, and pneumatic retinopexy. Various types of tamponades, including gas, silicone oil, and air, have been used. PPV was the most commonly used surgical technique in 33.1-100% of patients. Among the 20 studies that used PPV alone, 17 were associated with preoperative PVR. In addition, scleral buckling alone or in combination with PPV was reported as a treatment option in 10 studies, with 2-100% of patients experiencing scleral buckling alone and 13.6-100% experiencing combined PPV and complementary scleral buckling. Primary anatomic success (PAS) was achieved with retinal reattachment via a single operation with no residual tamponade, whereas final anatomic success (FAS) was achieved via more than one operation with no residual tamponade. Reported single surgery anatomic success (SSAS) rates range from 65.51 to 100%. The preoperative best-corrected visual acuity (BCVA) ranged from 0.067 to 2.47 logMAR, whereas the postoperative BCVA ranged from 0.08 to 2.3 logMAR. An improvement in visual acuity was observed in 29 studies. Cataracts (3.9-28.3%) were the most common postoperative complication, followed by high IOP (0.01-51.2%) and PVR (0.8-31.57%). CONCLUSION: PPV is the most common surgical technique, and currently microincision vitrectomy surgery (MIVS) systems are commonly employed. Silicone oil is the most frequently used tamponade in RRD repair. Risk factors for GRT-related RRD include age, sex, lens status, high myopia status, proliferative vitreoretinopathy (PVR), presenting visual acuity, the extent of the GRT and retinal detachment, and macular involvement. Future research areas include guidelines to reduce variability in the reporting of surgical methodology, choice of tamponades, and reporting of functional and visual outcomes to inform the best therapeutic interventions in GRT-related RRD.

New beam-based models for fire-induced buckling analysis of class 4 steel columns.

Steel cross-sections with thin walls are vulnerable to fire-induced buckling instability, which reduces their load-bearing capacity. Eurocode 3 design provisions have been found inadequate, leading to alternative methods such as effective design strategies and advanced structural models built mostly with shell FE, which can be complex. For Class 4 steel beam-columns subjected to fire conditions, beam-type modelling to predict the Flexural-Torsional Buckling (FTB) strength has been proposed as an alternative approach, but it has not yielded satisfactory results for large compressive load eccentricities. This paper presents two new low computational cost modelling strategies based on Timoshenko's beam FE to address this issue: the Single beam-column Model (SbcM) and the Cruciform beam-column Model (CbcM). The first consists of a single line of beam FE, while the second uses a grid of beam FE for more flexibility. Both strategies effectively simulate the FTB behaviour in Class 4 steel beam-column during a fire, offering quicker computations compared to shell models. Still, the single-line model is favoured for its simplicity, making it more efficient in analysing complex fire engineering problems.

Evaluation of the P-Δ (P-Delta) effect in columns and frames using the two-cycle method based on the solution of the beam-column differential equation.

P-Delta is a nonlinear phenomenon that results from the consideration of axial loads acting on the deformed configuration of a member of the structure, usually a beam-column. This effect is especially significant in slender members, which can undergo large transversal displacements which tend to increase the bending moment caused by an axial load P acting upon them. The P-delta effect can be computed through a geometrically nonlinear analysis, usually employing the Finite Element Method, which subdivides each bar of the frame in finite segments known as elements. Since discretization (subdivision) and the use of iterative schemes (like Newton-Raphson) are sometimes undesirable, especially for students, avoiding it can be didactically interesting. This work proposes the use of a new approach to perform a simplified nonlinear analysis using the two-cycle method and a tangent stiffness matrix obtained directly from the homogeneous solution of the problem's (beam-column) differential equation. The proposed approach is compared to the results obtained by the traditional two-cycle method which uses geometric and elastic stiffness matrices based on cubic (Hermitian) polynomials and a P-Delta approximation using the pseudo (fictitious) lateral load method.

Novel octa-graphene-like structures based on GaP and GaAs.

CONTEXT: The discovery of graphene gave way to the search for new two-dimensional structures. In this regard, octa-graphene is a carbon allotrope consisting of 4- and 8-membered rings in a single planar sheet, drawing the research community's attention to study their inorganic analogs. Considering the promising properties of octa-graphene-like structures and the role of GaAs and GaP in semiconductor physics, this study aims to propose, for the first time, two novel inorganics buckled nanosheets based on the octa-graphene structure, the octa-GaAs and octa-GaP. This work investigated the structural, electronic, and vibrational properties of these novel octa-graphene-based materials. The octa-GaP and octa-GaAs have an indirect band gap transition with a valence band maximum between M and Г points and a conduction band minimum at Г point with energy of 3.05 eV and 2.56 eV, respectively. The QTAIMC analysis indicates that both structures have incipient covalent in their bonds. The vibrational analysis demonstrates the occurrence of ΓRaman = 6Ag + 6Bg and ΓRaman = 12A' + 12B″ for octa-GaP and octa-GaAs, respectively. The symmetry reduction of octa-GaAs leads to activating inactive modes observed in the octa-GaP structure. The frontier crystalline orbitals are composed by Ga(px) and P(py and pz) orbitals for octa-GaP and Ga(px and py) and As(s, py, and pz) for octa-GaAs in the valence bands while in the conduction bands by Ga(py, pz, and s) for both compounds and P(px and pz) and As(py). The phonon bands demonstrate the absence of the negative frequency modes and the structural stability of these new nanosheets. This report aims to reveal the fundamental properties of both newfound materials for stimulating experimental research groups in the search for synthesis routes to obtain this structure. METHODS: This work used the DFT/B3LYP approach implemented in the CRYSTAL17 computational package. Ga, As, and P atomic centers were described by triple-zeta valence with polarization (TZVP) basis set. The vibrational analysis was carried out via coupled-perturbed Hartree-Fock/Kohn Sham (CPHF/KS) method, and the chemical bonds were evaluated via the quantum theory of atoms in molecules and crystals (QTAIMC).

Risk factors for failure after primary vitrectomy with no scleral buckling for rhegmatogenous retinal detachment / Fatores de risco para falha de tratamento após vitrectomia primária sem retinopexia com introflexão escleral

ABSTRACT Objective To assess pre-operative conditions that could influence primary anatomical success rate in a cohort of patients with rhegmatogenous retinal detachments (RRD) treated with primary vitrectomy and no scleral buckling. Methods A retrospective analysis was performed in a group of patients that underwent primary pars plana vitrectomy with gas tamponade and without scleral buckling for RRD between 2014 and 2019, with a minimum follow-up of 4 months. Results 305 eyes of 301 patients were included; 59.01% eyes were phakic, 39.01% were pseudophakic and 1.96% aphakic. 13.11% of patients had proliferative vitreoretinopathy grade B and 3.28% proliferative vitreoretinopathy grade C at the time of diagnosis while 83.61% had proliferative vitreoretinopathy grade 0 or A. 53.1% had superior breaks, 15.4% inferior breaks and 31.5% a combination of both. Primary success rate was obtained in 90.82% of eyes (95%CI 87.58-94.06). 9.18% of eyes (95%CI 5.94-12.42) re-detached. In 3.27% the cause of re-detachment was proliferative vitreoretinopathy, and in the remaining 5.90% because of a new or a missed break, the leakage of a previously treated break, or an area of shallow peripheral detachment with no detectable break. Of 181 phakic eyes, 10.49% re-detached, whereas in over 126 aphakic or pseudophakic eyes 7.75% re-detached (p=0.42). 16.39% eyes of the entire cohort had preoperative grade B or C proliferative vitreoretinopathy, whereas 32.14% of re-detached eyes had preoperative grade B or C proliferative vitreoretinopathy (95%CI 17.29-46.99; p=0.02). Th eyes that re-detached after the first surgery had a mean of 2.5 (95%CI 1.86-3.13) retinal tears, against a mean of 1.87 (95%CI 1.73-2.00) retinal tears of those that did not re-detach after the first surgery (p=0.02). Conclusion We found location of breaks and lens status to be independent factors not related to a lower single operation success rate, whereas the number or size of breaks and preoperative proliferative vitreoretinopathy stages B or C were independent factors related to a higher likelihood of re-detachment.

RESUMO Objetivo Avaliar condições pré-operatórias que poderiam influenciar a taxa de sucesso anatômico primário em uma coorte de pacientes com descolamento de retina regmatogênico tratada com vitrectomia primária e sem introflexão escleral. Métodos Foi realizada uma análise retrospectiva em um grupo de pacientes submetidos a vitrectomia primária pars plana com tamponamento gasoso e sem introflexão escleral por desprendimento de retina regmatogênico entre os anos 2014 e 2019, com monitoramento mínimo de 4 meses. Resultados Foram incluídos 305 olhos de 301 pacientes; 59,01% dos olhos eram fáquicos, 39,01% eram pseudofáquicos, e 1,96% era afáquico; 13,11% dos pacientes tinham vitreorretinopatia proliferativa grau B, e 3,28%, vitreorretinopatia proliferativa grau C no momento do diagnóstico, enquanto 83,61% tinham vitreorretinopatia proliferativa grau 0 ou A; 53,1% tinham rasgaduras superiores; 15,4%, rasgaduras inferiores e 31,5%, uma combinação de ambas. A taxa de sucesso primário foi obtida em 90,82% dos olhos (IC95% 87,58-94,06); 9,18% dos olhos (IC95% 5,94-12,42) se redestacaram. Em 3,27%, a causa do redescolamento foi vitreorretinopatia proliferativa e, nos 5,90% restantes, por causa de uma ruptura nova ou perdida, o vazamento de uma ruptura previamente tratada, ou uma área de descolamento periférico superficial sem ruptura detectável. Dos 181 olhos fáticos, 10,49% redestacaram-se, enquanto em mais de 126 olhos afáquicos ou pseudofáquicos 7,75% redestacaram-se (p=0,42); 16,39% dos olhos de toda a coorte tinham vitreorretinopatia proliferativa pré-operatória grau B ou C, enquanto 32,14% dos olhos redescolados tinham vitreorretinopatia proliferativa pré-operatória grau B ou C (IC95% 17,29-46,99) (p=0,02). Os olhos que se redescolaram após a primeira cirurgia tiveram média de 2,5 (IC95% 1,86-3,13) lágrimas retinianas, contra uma média de 1,87 (IC95% 1,73-2,00) lágrima retiniana daqueles que não se redestacaram após a primeira cirurgia. (p=0,02). Conclusão A localização das rasgaduras e o status da lente são fatores independentes não relacionados a uma menor taxa de sucesso da operação, enquanto o número ou o tamanho das rasgaduras e estágios vitreorretinopatia proliferativa pré-operatórios B ou C foram fatores independentes relacionados a uma maior probabilidade de redescolamento.

Mini vitrectomy as an alternative technique for intraocular pressure adjustment in non-drainage scleral buckling.

Purpose: In non-drainage scleral buckling, anterior chamber paracentesis is usually carried out to decrease intraocular pressure. When the buckling is extensive however, this technique may be inefficient and time consuming. In this study, we tried to determine if a mini 25-gauge pars plana vitrectomy could be used as an efficient and safe alternative procedure to anterior chamber paracentesis for adjusting intraocular pressure during a non-drainage scleral buckling. Methods: In this case series, 44 patients with rhegmatogenous retinal detachment (proliferative vitreoretinopathy stage < C) were included. In all cases, a mini 25-gauge pars plana vitrectomy was performed before buckle fixation and repeated if necessary. Complete retinal attachment was defined as the anatomical success. Results: Forty-four eyes of 44 patients with mean age of 48.1 ± 18.2 years were included. Silicon buckle nº 276, sponge 505, and sponge 507 were utilized for 7, 34, and 3 eyes, respectively. Intravitreal injection of SF6 gas was performed for 54.5% of the eyes. Mean total time of the operation was 61 ± 16 min and the mean time for vitrectomy was 87 ± 31 s. Complete retinal attachment in 37 and incomplete attachment in 4 eyes were achieved after single operation that was a success rate of 93.2%. One had more than usual vitreous leak at the site of scleretomy and one developed a tiny vitreous hemorrhage at the sclerotomy site. Three sclerotomy sites needed suturing. Conclusion: The anatomical outcome and the safety observed in this study were comparable to the current methods reported in the literature. Therefore, if anterior chamber paracentesis fails to adjust intraocular pressure during a non-drainage scleral buckling, performing a small gauge mini vitrectomy is safe and helpful.

The development of epiretinal membrane following rhegmatogenous retinal detachment repair: incidence, risk factors, and outcomes / Desenvolvimento da membrana epirretiniana após reparo do descolamento regmatogênico da retina: incidência, fatores de risco e resultados

ABSTRACT Purpose: To investigate the incidence, risk factors, and visual outcomes of epiretinal membrane development following rhegmatogenous retinal detachment repair. Methods: This was a retrospective study of 309 eyes that underwent initial surgery for primary uncomplicated rhegmatogenous retinal detachment. Examinations were conducted preoperatively and then postoperatively at 1, 3, 6, and 12 months. The study patients were categorized into two groups depending on the presence or absence of the epiretinal membrane. Results: The incidence of postoperative epiretinal membrane was 28.5%; 42.7% of these patients had severe epiretinal membrane development and therefore underwent the epiretinal membrane removal. Logistic regression analyses revealed that giant retinal tears (OR: 2.66; 95% CI: 1.045-6.792, p=0.040) and horseshoe tears (OR: 0.534; 95% CI: 0.295-0.967, p=0.039) were the significant predictors of postoperative epiretinal membrane. Triamcinolone acetonide staining was significantly associated with the prevention of epiretinal membrane (p=0.022). A total of 34 patients showed a better or an equal final best-corrected visual acuity; of which 4 eyes were evaluated at the final follow-up visit and exhibited a reduced best-corrected visual acuity. Conclusion: Our analysis demonstrated that horseshoe tears and giant retinal tears represent the risk factors for the postoperative epiretinal membrane. Triamcinolone acetonide staining had a significant preventive effect on the postoperative epiretinal membrane. Furthermore, a second round of pars plana vitrectomy, including membrane removal, led to a significant improvement in the final best-corrected visual acuity as per the last follow-up examination, albeit the recovery was limited.

RESUMO Objetivos: Investigar a incidência, fatores de risco e desfechos visuais do desenvolvimento da membrana epirretiniana após reparo do descolamento regmatogênico da retina. Métodos: Trata-se de um estudo retrospectivo de 309 olhos submetidos à cirurgia inicial para descolamento regmatogênico da retina primário sem complicações. Os exames foram realizados no pré-operatório aos 1, 3, 6 e 12 meses pós-operatórios. Os pacientes foram divididos em dois grupos, dependendo da presença ou ausência de membrana epirretiniana. Resultados: A incidência de membrana epirretiniana pós-operatória foi de 28,5%; 42,7% desses pacientes apresentaram desenvolvimento grave da membrana epirretiniana e, portanto, foram submetidos à remoção desta membrana. A regressão logística mostrou que as lágrimas retinianas gigantes (RC: 2,66; 95% IC: 1,045 - 6,792, p=0,040) e lágrimas em ferradura (RC: 0,534; 95% IC: 0,295-0,967, p=0,039), foram preditores significativos de membrana epirretiniana pós-operatória. A coloração com acetonida de triancinolona foi significativamente associada à prevenção da membrana epirretiniana (p=0,022). Trinta e quatro pacientes apresentaram acuidade visual melhorada, ou igual, ou acuidade visual final melhor corrigida; 4 olhos foram avaliados na consulta final de acompanhamento e apresentaram redução da acuidade visual melhor corrigida. Conclusão: Nossa análise demonstra que as lágrimas de ferradura e as lágrimas retinianas gigantes representam fatores de risco para a membrana epirretiniana pós-operatória. A coloração com acetonida de triancinolona teve um efeito preventivo significativo na membrana epirretiniana no pós-operatório. Além disso, uma segunda rodada de vitrectomia pars plana, incluindo remoção da membrana, levou a uma melhora significativa da acuidade visual final melhor corrigida na última consulta de acompanhamento, embora a recuperação tenha sido limitada.

Mini vitrectomy as an alternative technique for intraocular pressure adjustment in non-drainage scleral buckling / La minivitrectomía como técnica alternativa para el ajuste de la presión intraocular en el cerclaje escleral sin drenaje

Purpose: In non-drainage scleral buckling, anterior chamber paracentesis is usually carried out to decrease intraocular pressure. When the buckling is extensive however, this technique may be inefficient and time consuming. In this study, we tried to determine if a mini 25-gauge pars plana vitrectomy could be used as an efficient and safe alternative procedure to anterior chamber paracentesis for adjusting intraocular pressure during a non-drainage scleral buckling. Methods: In this case series, 44 patients with rhegmatogenous retinal detachment (proliferative vitreoretinopathy stage < C) were included. In all cases, a mini 25-gauge pars plana vitrectomy was performed before buckle fixation and repeated if necessary. Complete retinal attachment was defined as the anatomical success. Results: Forty-four eyes of 44 patients with mean age of 48.1 ± 18.2 years were included. Silicon buckle nº 276, sponge 505, and sponge 507 were utilized for 7, 34, and 3 eyes, respectively. Intravitreal injection of SF6 gas was performed for 54.5% of the eyes. Mean total time of the operation was 61 ± 16 min and the mean time for vitrectomy was 87 ± 31 s. Complete retinal attachment in 37 and incomplete attachment in 4 eyes were achieved after single operation that was a success rate of 93.2%. One had more than usual vitreous leak at the site of scleretomy and one developed a tiny vitreous hemorrhage at the sclerotomy site. Three sclerotomy sites needed suturing. Conclusion: The anatomical outcome and the safety observed in this study were comparable to the current methods reported in the literature. Therefore, if anterior chamber paracentesis fails to adjust intraocular pressure during a non-drainage scleral buckling, performing a small gauge mini vitrectomy is safe and helpful.

Lightweight Design of Variable-Stiffness Cylinders with Reduced Imperfection Sensitivity Enabled by Continuous Tow Shearing and Machine Learning.

The present study investigates how to apply continuous tow shearing (CTS) in a manufacturable design parameterization to obtain reduced imperfection sensitivity in lightweight, cylindrical shell designs. The asymptotic nonlinear method developed by Koiter is applied to predict the post-buckled stiffness, whose index is constrained to be positive in the optimal design, together with a minimum design load. The performance of three machine learning methods, namely, Support Vector Machine, Kriging, and Random Forest, are compared as drivers to the optimization towards lightweight designs. The new methodology consists of contributions in the areas of problem modeling, the selection of machine learning strategies, and an optimization formulation that results in optimal designs around the compromise frontier between mass and stiffness. The proposed ML-based framework proved to be able to solve the inverse problem for which a target design load is given as input, returning as output lightweight designs with reduced imperfection sensitivity. The results obtained are compatible with the existing literature where hoop-oriented reinforcements were added to obtain reduced imperfection sensitivity in composite cylinders.

Enlightening new underpinnings in hydration retinal folds.

PURPOSE: To describe and value a peculiar alteration typically found in rhegmatogenous retinal detachment raising news foundations of its role in the photoreceptors and visual prognosis. DESIGN: Case description and rationale formulation. SUBJECTS: An isolated case. INTERVENTION: We report a case of a 52-year-old male patient complaining of sudden visual acuity (VA) loss in the left eye. Fundoscopic findings revealed rhegmatogenous retinal detachment, macula off, and an isolated horseshoe tear in the infero-temporal periphery. Spectral-domain optical coherence tomography (SD-OCT) evinced prominent hydration retinal folds. MAIN OUTCOME MEASURES: Restructuring of the retinal layers, visual acuity and complaints. RESULTS: The patient underwent scleral buckling surgery with complete re-attachment of the retina and significant improvement of the hydration retinal folds. In addition, there was resolution of visual symptoms, with a final VA of 20/30. CONCLUSIONS: We speculate that the increase in arc length of the outer retina generates a centripetal force towards the fovea. Its association with the higher density of photoreceptors in this region, generates resistance in the water inflow, preventing swelling and cellular damage of the central photoreceptors.

Identación escleral y retinopexia neumática / Scleral buckling and neumatic retinopexy

Objetivo: Determinar los resultados de la técnica quirúrgica de identación escleral y la de retinopexia neumática en el desprendimiento regmatógeno de retina. Métodos: Se realizó un estudio descriptivo, longitudinal y prospectivo en pacientes operados con la técnica de identación escleral y la de retinopexia neumática en el Centro Oftalmológico de Villa Clara entre junio de 2019 y diciembre de 2020. Resultados: Los hombres fueron los más afectados y la edad media fue de 57,5 años. En el 72,7 por ciento la rotura causante del desprendimiento fueron los desgarros en herradura. La media del tiempo de evolución de la enfermedad fue de 7,2 días y el 77,3 por ciento de los ojos presentaba mácula desprendida al momento del diagnóstico. El 68,2 por ciento tuvo una agudeza visual mejor corregida preoperatoria < 20/200. Los pacientes con mácula desprendida preoperatoria alcanzaron como media una agudeza visual final de 0,4 ± 0,3 (desviación estándar). En el 86,4 y el 77,3 por ciento de los ojos se lograron buenos resultados anatómicos y funcionales finales. Las membranas epirretinales se presentaron como complicación posoperatoria en ambas técnicas quirúrgicas y el líquido subretinal residual solo en la retinopexia neumática. Conclusiones: El desprendimiento regmatógeno de retina se presenta con pobre agudeza visual preoperatoria. Con ambas técnicas quirúrgicas, en pacientes con ninguna o mínima vitreorretinopatía proliferativa, se logran buenos resultados anatómicos y funcionales.

Objective: Determine the results of the surgical technique of scleral buckling and neumatic retinopexy in rhegmatogenous retinal detachment. Methods: A prospective longitudinal descriptive study was conduced of patients undergoing scleral buckling and neumatic retinopexy at Villa Clara Ophthalmology Center from June 2019 to December 2020. Results: Male gender prevailed; mean age was 57.5 years. In 72.7 percent of the cases the retinal break causing the detachment was a U-shaped tear. Mean time of evolution of the disease was 7.2 days, and 77.3 percent of the eyes had a detached macula at diagnosis. In 68.2 percent preoperative best corrected visual acuity was <20/200. Patients with a preoperative detached macula achieved a mean final visual acuity of 0.4 ± 0.3 (standard deviation). Good final anatomical and functional results were obtained in 86.4 percent and 77.3 percent of the eyes. Epiretinal membranes were a postoperative complication in both surgical techniques, whereas residual subretinal fluid was a complication only in neumatic retinopexy. Conclusions: Rhegmatogenous retinal detachment presents with poor preoperative visual acuity. Both surgical techniques obtain good anatomical and functional results in patients with minimum or no proliferative vitreoretinopathy(AU)

Bending, buckling and torsional resistance of rotary and reciprocating glide path instruments.

AIM: To evaluate the bending, buckling and torsional resistance of ProGlider (PG) (Dentsply Sirona, Ballaigues, Switzerland), R-Pilot (RP) (VDW, Munich, Germany) and WaveOne Gold Glider (WOGG) (Dentsply Sirona). METHODOLOGY: Ninety instruments were used: 30 PG (size 0.16, .02v taper), 30 RP (size 0.125, .04 taper) and 30 WOGG (size 0.15, .02v taper). The bending resistance test was performed on 10 randomly selected instruments of each system according to ISO 3630-1 specifications. For the buckling resistance test, a loading was applied in the axial direction of each instrument using a universal test machine, with a 20 N cell and 15 mm min-1 speed, in the axial direction. When a lateral elastic displacement of 1 mm occurred, the force was registered. The torsional resistance test was performed according to ISO 3630-1 specifications. Statistical analysis was performed using one-way anova and post hoc Student-Newman-Keuls test (P < 0.05). RESULTS: WOGG had the lowest bending resistance, whilst RP had the highest bending resistance (P < 0.05). RP also had the highest buckling resistance, and WOGG had the lowest (P < 0.05). PG had intermediate results regarding bending and buckling resistance, with significant differences to RP and WOGG (P < 0.05). RP had the highest torsional strength and the lowest angular deflection when compared to PG and WOGG (P < 0.05). No differences in the torsional strength and angular deflection were observed between WOGG and PG (P> 0.05). CONCLUSION: The glide path instruments had different behaviours in term of bending, buckling and torsional resistance.

Scaling of stem diameter and height allometry in 14 neotropical palm species of different forest strata.

Tropical palms reach tree-like heights without a vascular cambium through sustained cell expansion and lignification of primary tissues, but only a fraction of palms have been explored in their allometric relationships. Here, our main question was to determine how palms depart from the traditional mechanical models developed for trees and how they approach the theoretical buckling limit. We analyzed the stem allometry of 1603 palms of 14 species from different strata at 10 sites in Costa Rica and Peru. We measured their fit to the stress, elastic, and geometric similarity models, and their position relative to the maximum theoretical buckling limit calculated for trees. We evaluated the slope of the linear and logarithmic regressions between stem diameter and height using logarithmic least squares, and standardized major axis regression (SMA), expecting segregation according to canopy position and geographic location. Seventeen out of 19 statistically significant models had SMA slopes > 1, and 11 had SMA slopes ≥ 2, departing from traditional mechanical models developed for trees. Many species varied their allometry relative to geographic location. Canopy palms showed the highest regression fit but had less steep slopes than understory and subcanopy species. Subcanopy and understory species were more underbuilt than canopy palms, increasing height faster than diameter. Some of the tallest canopy palms surpassed the maximum buckling limit whereas subcanopy and understory species were consistently below the buckling limit of record-size trees. Palm stem allometry changed in response to environmental conditions.

A new instrument to simplify encircling buckle placement.

PURPOSE: The purpose of this study is to describe a new surgical instrument that simplifies 360° silicone band placement, alone or in combination with pars plana vitrectomy, for the treatment of rhegmatogenous retinal detachment. METHODS: The instrument has a straight shank and a curved component in the form of a partial helix, whose purpose is to encircle the perimeter of the eye globe below the rectus muscles. The distal tip of the helix is inserted through a small conjunctival incision in the superior temporal quadrant, and the shank is rotated 360° on its axis until the tip emerges from the insertion point. One end of the silicone band is sutured to the tip, and the instrument is rotated in the opposite direction until both ends of the band are positioned in the same scleral quadrant. The band is sutured to the sclera and the conjunctival incision is closed. Pars plana vitrectomy can then be performed using transconjunctival microincision techniques through the intact conjunctiva. RESULTS: Our experience using the instrument in more than 100 procedures has shown that the new technique considerably reduces surgical trauma: wide opening of the conjunctiva is obviated, there is little manipulation of the extraocular musculature, and only a few sutures are needed. The duration of the procedure is considerably shorter because of the smaller number of surgical maneuvers. CONCLUSION: We describe a new scleral technique facilitated by this surgical instrument, whose objective is safe and effective placement of an encircling silicone band with minimum trauma and a reduction in operating time.

Surgical outcomes of rhegmatogenous retinal detachment associated with ocular toxoplasmosis / Resultados cirúrgicos do descolamento regmatogênico de retina associado à toxoplasmose ocular

ABSTRACT Purpose: To evaluate the anatomical and functional outcomes of surgical treatment of retinal detachment secondary to ocular toxoplasmosis. Methods: A retrospective analysis of data from patients who had undergone vitreoretinal surgery for retinal detachment secondary to ocular toxoplasmosis was conducted. The parameters that were analyzed include surgical procedures, anatomical outcomes, visual acuity, and postoperative complications. Results: This study included 22 patients, of which 13 were female (59.1%). The mean age was 28.5 years (SD ± 14.5, range 12-78 years) and the follow-up period varied from 1 to 163 months (mean 64 months). The mean baseline best-corrected visual acuity (BCVA) was 2.0 logMAR (SD ± 1.0). A total of 31 surgeries were performed, and the retina was reattached in 15 patients (68.2%) immediately after the first surgery and in 20 patients (90.9%) at a later point. The mean postoperative BCVA improved to 1.3 logMAR (SD ± 0.9) (p<0.05). Nineteen patients (86.4%) underwent cataract surgery with intraocular lens implant, and 12 patients (60.0%) underwent silicone oil removal. Five patients (22.7%) exhibited elevated intraocular pressure, and 1 patient (4.5%) developed hypotonia. Conclusion: Surgical treatment of retinal detachment secondary to ocular toxoplasmosis resulted in considerable anatomical and functional improvement. Although PPV with silicone oil injection demonstrated the best outcomes, it is not reasonable to conclude that this is the best surgical approach given the small number of patients included in this study.

RESUMO Objetivo: Avaliar os resultados anatômicos e funcionais após o tratamento do descolamento de retina secundário à toxoplasmose ocular. Métodos: Análise retrospectiva de dados de um banco de dados validado, que incluiu registros de pacientes submetidos à cirurgia vitreorretiniana para descolamento de retina secundário a toxoplasmose ocular. Foram analisados procedimentos cirúrgicos, sucesso anatômico, acuidade visual e complicações pós-operatórias. Resultados: Foram avaliados 22 olhos de 22 pacientes. Treze eram do sexo feminino (59,1%) e a idade média era de 28,5 anos (DP ± 14,5, intervalo de 12 a 78 anos). O período de acompanhamento variou de 1 a 163 meses (média de 64 meses). A melhor acuidade visual corrigida (BCVA) foi 2,0 logMAR (SD ± 1,0). Em geral, entre retinopexia (RSB) e vitrectomia pars plana (PPV) utilizando injeção de óleo de gás ou de silicone (SO), realizaram-se 31 cirurgias. A retina foi considerada colada em 15 olhos (68,2%) na primeira cirurgia e em 20 olhos (90,9%) ao final do estudo. A BCVA pós-operatória média melhorou para 1,3 logMAR (SD ± 0,9) (p<0,05). Dezenove olhos (86,4%) foram submetidos à cirurgia de catarata com implante de lente intraocular e 12 olhos (60,0%) tiveram remoção de óleo de silicone. Cinco olhos (22,7%) desenvolveram pressão intraocu­lar elevada e 1 (4,5%) desenvolveu hipotonia. Conclusão: A abordagem cirúrgica no descolamento de retina secundária a toxoplasmose ocular permitiu importante melhora anatômica e funcional. Embora a PPV com injeção de óleo de silicone tenha demonstrado melhores resultados, não é viável afirmar que é a melhor técnica cirúrgica, devido ao pequeno número e às particularidades dos olhos tratados.

Characterization of microtubule buckling in living cells.

Microtubules are filamentous biopolymers involved in essential biological processes. They form key structures in eukaryotic cells, and thus it is very important to determine the mechanisms involved in the formation and maintenance of the microtubule network. Microtubule bucklings are transient and localized events commonly observed in living cells and characterized by a fast bending and its posterior relaxation. Active forces provided by molecular motors have been indicated as responsible for most of these rapid deformations. However, the factors that control the shape amplitude and the time scales of the rising and release stages remain unexplored. In this work, we study microtubule buckling in living cells using Xenopus laevis melanophores as a model system. We tracked single fluorescent microtubules from high temporal resolution (0.3-2 s) confocal movies. We recovered the center coordinates of the filaments with 10-nm precision and analyzed the amplitude of the deformation as a function of time. Using numerical simulations, we explored different force mechanisms resulting in microtubule bending. The simulated events reproduce many features observed for microtubules, suggesting that a mechanistic model captures the essential processes underlying microtubule buckling. Also, we studied the interplay between actively transported vesicles and the microtubule network using a two-color technique. Our results suggest that microtubules may affect transport indirectly besides serving as tracks of motor-driven organelles. For example, they could obstruct organelles at microtubule intersections or push them during filament mechanical relaxation.

Desgarro retiniano posterior, asociado a LASIK en miopía. Su tratamiento en 1989 y evaluación en 2015 / Posterior retinal tear, myopia and LASIK. Its treatment in 1989 and follow up in 2015

Caso de desgarro retiniano posterior grande, paravascular, inferotemporal en ojo izquierdo, con desprendimiento de retina y hemorragia vítrea parcial en mujer de 30 años, miope de -5.00 dioptrías. El relato de su tratamiento, resultados inmediatos obtenidos en 1989 y su seguimiento tardío con valoración actualizada en 2015.

Case of large posterior, paravascular, inferotemporal retinal tear associated with a partial vitreous emorrhage and a quadrantic retinal detachment in a 30 years old myopic woman of -5.00 diopters. Management, initial results in 1989 and follow-up with current evaluation in 2015.

Corneal topographic changes after 20-gauge pars plana vitrectomy associated with scleral buckling for the treatment of rhegmatogenous retinal detachment

PURPOSE: To evaluate the changes in corneal topography after 20-gauge pars plana vitrectomy associated with scleral buckling for the repair of rhegmatogenous retinal detachment. METHODS: Twenty-five eyes of 25 patients with rhegmatogenous retinal detachment were included in this study. 20-gauge pars plana vitrectomy associated with scleral buckling was performed in all patients. The corneal topography of each was measured before surgery and one week, one month, and three months after surgery by computer-assisted videokeratoscopy. RESULTS: A statistically significant central corneal steepening (average, 0,9 D , p<0,001) was noted one week after surgery. The total corneal astigmatism had a significant increase in the first postoperative month (p=0,007). All these topographic changes persisted for the first month but returned to preoperative values three months after the surgery. CONCLUSION: Pars plana vitrectomy with scleral buckling was found to induce transient changes in corneal topography.

OBJETIVO: Avaliar as alterações topográficas da córnea após a realização de vitrectomia via pars plana 20-gauge associada à introflexão escleral para o tratamento do descolamento de retina regmatogênico. MÉTODOS: Vinte e cinco pacientes com descolamento de retina regmatogênico foram incluídos neste estudo. Vitrectomia via pars plana 20-gauge associada à introflexão escleral foi realizada em todos os pacientes. O exame de topografia de córnea computadorizada de cada paciente foi realizado antes da cirurgia e ao sétimo dia, trigésimo dia e três meses após a cirurgia. RESULTADOS: Um aumento da curvatura corneana estatisticamente significativo foi encontrado no sétimo dia após a cirurgia (média 0,9 D, p<0,001). O astigmatismo corneano total teve um aumento significativo no primeiro mês pós-operatório (p=0,007).Todas as alterações topográficas persistiram no primeiro mês pós-operatório, mas retornaram aos valores pré-operatórios três meses após a cirurgia. CONCLUSÃO: A vitrectomia via pars plana associada à introflexão escleral pode induzir alterações transitórias na topografia corneana.

Scleral buckle is good option for treatment of uncomplicated retinal detachment / Introflexão escleral é boa opção para tratamento de descolamento de retina não complicado

OBJETIVE: To describe the reattachment rate and visual acuity results of patients with uncomplicated rhegmatogenous retinal detachment who underwent segmental scleral buckle surgery. METHODS: Prospective case series of 100 patients with visual loss or symptoms (floaters and photopsia) of less than 30 days' duration scheduled for surgery. No patient had a retinal break greater than 30°, a retinal detachment larger than 2 quadrants or proliferative vitreoretinopathy. RESULTS: The 1-week, 1-month, and 6-month anatomical success rates were 93%, 100%, and 100%, respectively. Seven patients underwent one additional retinal detachment surgery (pars plan vitrectomy) after primary failure at 1-week follow-up. The preoperative, 1-month, and 6-month best correct visual acuity were 20/100, 20/80, and 20/50, respectively. The postoperative complications were: eyelid edema in 10% of the patients, transient ocular hypertension in 5%, macular pucker in 3%, transient diplopia in 3%, and hyphema (<0.5mm) in 1%. CONCLUSION: In patients with uncomplicated retinal detachment, segmental scleral buckle showed a very good anatomical and functional success, with a few number of major complications.

OBJETIVO: Descrever a taxa de reaplicação e os resultados da acuidade visual dos pacientes com descolamento de retina regmatogênico simples que se submeteram à cirurgia de introflexão escleral segmentar. MÉTODOS: Uma série de casos prospectivo de 100 pacientes com perda visual ou sintomas (floaters e fotopsia), com duração inferior a 30 dias, agendados para a cirurgia. Nenhum paciente apresentou uma ruptura da retina superior a 30°, um descolamento de retina maior que 2 quadrantes ou vitreorretinopatia. RESULTADOS: As taxas de sucesso anatômico em 1 semana, 1 mês e 6 meses foram de 93%, 100% e 100%, respectivamente. Sete pacientes foram submetidos à cirurgia de descolamento de retina adicional (vitrectomia via pars plana) após falha primária em uma semana de seguimento. A melhor acuidade visual pré-operatória, 1 mês, e de 6 meses pós-operatório foram 20/100, 20/80 e 20/50, respectivamente. As complicações pós-operatórias foram: edema palpebral em 10% dos pacientes, a hipertensão ocular transitória em 5%, pucker macular em 3%, diplopia transiente em 3%, e hifema (<0,5 mm) em 1%. CONCLUSÃO: Em pacientes com descolamento da retina sem complicações, a cirurgia de introflexão segmentar escleral mostrou um sucesso anatômico e funcional muito bom, com um número menor de complicações maiores.

Pyogenic granuloma after retinal detachment surgery with scleral buckle: case report / Granuloma piogênico após cirurgia de descolamento de retina com introflexão escleral: relato de caso

The authors relate an uncommon case of pyogenic granuloma restricted to tarsal conjunctiva post retinopexy with scleral buckle.

Os autores relatam um caso de granuloma piogênico subconjuntival pós retinopexia com introflexão escleral. É uma complicação pós-cirúrgica incomum neste tipo de procedimento.