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Analytical transmission electron microscopy (TEM) is often used to investigate morphologies, crystal structures, chemical compositions and oxidation states of highly reactive mixed-valent mineral phases. Of prime interest, due to its potential role in toxic metal remediation, is green rust sulphate (GR SO4 ) an Fe II -Fe III layered double hydroxide. In this study, we quantified the effects that TEM analysis has on GR SO4 in order to ensure the measured material properties are a result of synthesis and reaction kinetics, and not due to sample preparation and analysis technique. To do this, we compared two sample preparation techniques (anoxic drop-cast with drying, and frozen-hydrated cryogenic) and exposed samples to the electron beam for several minutes, acquiring fluence series between ca. 40 e -  Å -2 and 10,000 e -  Å -2 . TEM imaging and electron diffraction showed that the hexagonal plate-like morphology and crystal structure of GR SO4 were largely unaffected by sample preparation and analysis technique. However, quantitative analysis of a series of monochromated Fe L 3,2 -edge electron energy loss spectra (EELS) showed that electron irradiation induces oxidation. We measured an Fe(II)/Fe(III) ratio of 1.94 (as expected for GR SO4 ) at 50 e -  Å -2 . However, above this fluence, the ratio logarithmically decreased and dropped to ca. 0.5 after 1000 e -  Å -2 . This trend was approximately the same for both sample preparation techniques implying that it is the beam alone which causes valence state changes, and not exposure to oxygen during transfer into the TEM or the vacuum of the TEM column. Ultimately this work demonstrates that GR valence can be quantified by EELS provided that the sample is not over exposed to electrons. This also opens the possibility of quantifying the effect of redox-sensitive toxic metals (e.g., As, Cr, Se) on Fe oxidation state in GR phases (relevant to the treatment of contaminated soils and water) with a higher spatial resolution than other techniques (e.g., Mössbauer spectroscopy)., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Background: As part of the design of the Silicone Study, a new classification of proliferative vitreoretinopathy (PVR) was developed that distinguishes the different types of contraction found in PVR. In contrast to the original Retina Society system that emphasized the post-equatorial retinal pathology (posterior PVR), the Silicone Study classification system included the characteristic types of contraction found in both the equatorial region and the pre-equatorial retina and vitreous base (anterior PVR)., Methods: The authors contrast (1) preoperative and intraoperative findings and (2) vision and anatomic outcomes in the cohort of anterior PVR eyes with the cohort of posterior-only PVR eyes. For the cohort of eyes randomized to perfluoropropane gas (C3F8) or silicone oil, the authors carry out univariate and multivariate analyses to assess the predictive value of baseline and intraoperative parameters on vision and anatomic outcome., Results: Anterior PVR was present in 321 eyes (79%) and was more prevalent in eyes that had undergone an unsuccessful vitrectomy before study entry than in eyes that underwent a primary vitrectomy for PVR (88% versus 73%; P < 0.001). Compared with eyes that had posterior PVR at the preoperative examination, eyes that had anterior PVR tended to (1) be graded (Retina Society classification system) as D-1 or worse (86% versus 49%; P < 0.0001), (2) have worse (< 2/200) visual acuity (93% versus 86%; P = 0.003), (3) have more hypotony (24% versus 11%; P = 0.03), more edema (8% versus 2%; P = 0.04), more aqueous flare (P = 0.02), more macular pucker (69% versus 52%; P = 0.005), and more intravitreal contraction (21% versus 6%; P = 0.002). When compared with eyes that had anterior PVR, eyes with posterior PVR had a better outcome at the 6-month postoperative examination: complete attachment of the retina (76% versus 62%; P = 0.04), visual acuity of 5/200 or better (64% versus 45%; P = 0.006), and normal intraocular pressure (86% versus 71%; P = 0.04). For eyes with anterior PVR, significant predictors of poor (< 5/200) visual acuity were a preoperative PVR grade D-1 or worse and the use of C3F8 gas as the intraocular tamponade., Conclusion: The Silicone Study classification of anterior PVR permits greater specificity in characterizing PVR and is prognostic of anatomic and vision outcome. Eyes with anterior PVR and clinically significant posterior PVR changes had a better visual prognosis if silicone oil was used. With the current understanding of the pathoanatomy of anterior PVR and the recent development of new surgical techniques, the incidence of anterior PVR in eyes that previously underwent vitrectomy may decline, and the prognosis in eyes with anterior PVR may improve.

Background: Perfluoropropane (C3F8) is a valuable adjunct in the management of complex rhegmatogenous retinal detachments, and it has become the most commonly used perfluorocarbon gas. However, there have been few large reports about its complications. This retrospective study was undertaken to evaluate the complications of the use of perfluoropropane gas., Methods: Perfluoropropane gas was used in the repair of a complex retinal detachment in 157 consecutive eyes. Only eyes that had a follow-up of 6 months or greater were included. Any eyes that had undergone previous vitrectomy and vitreous substitution with gas or silicone oil were excluded., Results: Gas-induced lens opacities developed in 26 (67%) phakic eyes; transient increased intraocular pressure developed postoperatively in 50 (32%) eyes; a transient fibrinous, pupillary membrane developed in 20 (13%) eyes; and a flat anterior chamber developed in 10 (6%) eyes., Conclusions: Scleral buckle placement and increased gas concentration were found to be risk factors for the development of increased intraocular pressure. Proliferative diabetic retinopathy was associated with a higher development of lens opacities and pupillary membranes. No major complications were associated with the use of C3F8.

Background: The prevalence of postoperative macular pucker and the factors associated with its development after successful surgery for proliferative vitreoretinopathy (PVR) using silicone oil or gas tamponade are unknown., Methods: The postoperative status of the macula was determined by reviewing the photographs of 336 eyes taken 6 months after randomization. Two hundred eleven eyes with attached maculas were identified and analyzed to determine the prevalence of macular pucker after silicone oil and gas tamponades in eyes without (group 1) and with (group 2) previous vitrectomy surgery. Data obtained at baseline, from the primary study surgery, and from subsequent examinations and repeat surgeries during a follow-up period of 6 months were analyzed for factors associated with postoperative macular pucker., Results: The 6-month-point prevalence rate of postoperative macular pucker was 15% (32 of 211 eyes). Ten of the 32 eyes were new cases of macular pucker. The authors were unable to document a difference in the 6-month-point prevalence of postoperative macular pucker between group 1 and group 2 eyes (13% versus 18%) or between eyes randomized to gas versus silicone oil (19% versus 12%). Postoperative pucker was three times as likely to develop in aphakic/pseudophakic eyes compared with phakic eyes (P = 0.02). Focal contraction posteriorly causing starfolds, and intravitreal contraction involving the vitreous base or vitreous cavity, were significantly less prevalent in eyes with postoperative macular pucker (P < 0.05). Large (> or = 2 disc diameters) retinal breaks (P = 0.04) were associated significantly with postoperative macular pucker (P = 0.04). The authors were unable to document an association between postoperative macular pucker and the type of adhesive modality used or the extent of its application. Postoperative visual acuity was significantly better if the macula was not puckered (P < 0.01)., Conclusions: The occurrence of macular pucker after successful surgery for retinal detachments complicated by severe PVR is not influenced by the choice of intraocular tamponade. Certain preoperative factors may be associated with postoperative macular pucker.

The Retinal Society classification on proliferative vitreoretinopathy of 1983 has been updated to accommodate major progress in understanding of this disease. There are three grades describing increasing severity of the disease. Posterior and anterior location of the proliferations have been emphasized. A more detailed description of posterior and anterior contractions has been made possible by adding contraction types such as focal, diffuse, subretinal, circumferential contraction, and anterior displacement. The extent of the abnormality has been detailed by using clock hours instead of quadrants.

We studied the fellow eyes of eyes with macular holes by fundus photography, fluorescein angiography, and central visual field testing. Eight of 37 fellow eyes (22%) observed for a minimum of 36 months developed macular holes. Fellow eyes initially classified as normal developed fewer macular holes than fellow eyes with initial pigment epithelial defects or cystic formation.

The effects of an incision through the pars plana ciliaris for open-sky subtotal vitrectomy were evaluated in four groups of monkeys, with incisions ranging from 170 degrees to 240 degrees. The nasal long ciliary artery and nerve and the anterior ciliary arteries from the inferior and medial recti were left intact in all cases. Follow-up observation ranging from three to 24 months indicates that the 170 degrees incision and the longer incisions in which the temporal ciliary artery and nerve were sacrificed do not cause severe anterior segment necrosis. The advantages of the incision through the pars plana ciliaris are (1) easier approach to the vitreous cavity, (2) preservation of the crystalline lens and an intact iris, and (3) circumvention of the corneal and chamber angle complications sometimes associated with the transcorneal approach.

To study the value and the proper timing of vitrectomy in cases of ocular trauma involving the posterior segment, 24 rabbit eyes were traumatized by introducing a steel foreign body and autogenous blood into the vitreous. Twelve eyes underwent vitrectomy, 6 in the first week after trauma ("early") and 6 in the fourth week ("late"). The other 12 eyes, which underwent removal of the foreign body but not vitrectomy, served as controls. Traction retinal detachment did not develop in the 6 early-vitrectomy eyes, but it did occur before vitrectomy in 4 of the 6 eyes of the late-vitrectomy group and in 6 of the 12 control eyes. Iatrogenic cataract and retinal breaks were twice as frequent in the late as in the early group. The data seem to favor early vitrectomy in eyes with posterior-segment trauma. However, in routine clinical practice we advise prompt primary repair and exploration to evaluate the extent of posterior-segment damage, and vitrectomy within 14 days after injury.

A specially designed silicone balloon, expanded in vivo with normal saline, was tested for possible use as a retinal tamponade in desperate cases of rhegmatogenous retinal detachment. In six pigmented rabbits there were extensive postoperative complications, but in eight owl monkeys results were noticeably better. When the seam of the balloon was in contact with the retina there were adverse effects; seamless areas of the balloon did not appear to disturb the retina. Histopathologic studies indicated that excessive expansion of the balloon can cause significant damage, but that carefully controlled expansion can probably minimize complications. The presence of the balloon appears to alter electroretinographic response, but without necessarily causing histopathologic changes. Balloons of this type have been used in treatment of a small number of otherwise inoperable cases of retinal detachment with promising results.

Proliferative vitreoretinopathy (PVR) involving the posterior and equatorial retina is an established clinicopathologic entity. Clinically, a similar process, anterior PVR (APVR), results in anterior dragging of the peripheral retina by membranes which connect to the ciliary body or iris and cause circumferentially and radially fixed retinal folds. The pathology of APVR, however, has not been reported. The authors describe pathologic findings in 28 cases of APVR and ultrastructural pathologic findings in 6 surgical APVR specimens. Anterior PVR was frequently associated with retinal detachment (RD) repair (96%) and trauma (38%). Residual vitreous at the vitreous base virtually always provided a scaffold for membranes containing proliferating cells and deposited extracellular matrix. Major components of APVR membranes were fibrovascular tissue (71%), pigment epithelial cells (43%), fibrous and corneal stromal ingrowth (32%), and glial proliferation (18%). Because of its anterior location, APVR membranes also incorporated ciliary epithelium and corneal endothelium. Contraction of APVR membranes caused anterior retinal displacement and detachment in anatomic configurations corresponding to narrow and wide peripheral troughs. The authors' findings indicate that APVR is a distinctive clinicopathologic entity which may complicate rhegmatogenous RD and its repair.

In a 28-year-old man with bilateral acute retinal necrosis, a severe, bilateral panuveitis, necrotizing retinitis, and retinal vasculitis developed. Severe vitreous traction on atrophic retina resulted in bilateral giant retinal tears with an inoperable retinal detachment in the right eye. A retinal detachment developed in the left eye that was reattached after a pars plana vitrectomy and two scleral buckling procedures, but ultimately became inoperable. Large numbers of lymphocytes in the vitreous aspirate and depressed serum complement levels may indicate that an immune mechanism was involved in the necrotizing retinitis. We present the first electron microscopic evidence, to our knowledge, that preretinal membranes occurring in rhegmatogenous retinal detachment due to bilateral acute retinal necrosis arise from retinal pigment epithelium.

A 47-year-old male from India was treated for the rare condition of bilateral multifocal intraocular infestation with Cysticercus cellulosae, the larval form of Taenia solium. The intravitreous parasite in the left eye was removed via pars plana vitrectomy. A subretinal cysticercus in the right eye, which caused a rhegmatogenous retinal detachment, was removed via sclerotomy during the scleral buckling procedure. An additional peripapillary subretinal cyst could not be removed. A subconjunctival cysticercus was incidentally found and removed at the time of surgery. The patient returned to India six weeks after surgery and is doing well.

INCIDENCE OF RETINAL BREAKS AND DETACHMENT IN FELLOW EYES. The fellow eyes of 226 giant retinal breaks were followed in order to determine the incidence and natural course of chorioretinal and vitreous pathology. During the period of observation which ranged from 18 months to 16 years, the incidence of retinal breaks and retinal detachment increased from 36.1 percent to 51.3 percent. By the end of the follow-up period, the incidence of bilateral giant retinal breaks was 12.8 percent; retinal tears 11.9 percent, retinal holes 10.2 percent, retinal dialysis 0.4 percent, and retinal detachment 15.9 percent. The average duration of follow-up was 3.7 years, therefore, the incidence of retinal breaks in fellow eyes is probably significantly higher. VITREORETINAL CHANGES PRECEDING THE DEVELOPMENT OF RETINAL BREAKS. Syneresis, liquefaction, and condensation of the vitreous base were observed in the majority fellow eyes that developed retinal tears or giant retinal breaks. Follow-up of fellow eyes revealed that the development of a giant retinal break is often preceded by increasing white with pressure associated with increasing condensation of the vitreous base. MANAGEMENT OF FELLOW EYES. Bcause of the high incidence of retinal breaks developing in the fellow eye, regular and thorough examination of the vitreous and retinal breaks even though the fundus may appear normal at the initial examination. PROPHYLACTIC TREATMENT. This study suggests that prophylactic treatment is beneficial in the management of fellow eyes of giant retinal breaks. During this study, retinal breaks developed in 27.3 percent of untreated eyes and in 2.4 percent of eyes treated prophylactically. PROPHYLACTIC TREATMENT OF FELLOW EYES OF GIANT RETINAL BREAKS. Its seems prudent to prophylactically treat retinal holes or dialyses in eyes without retinal detachment with cryotherapy. Scleral bucking seems justified in the prophylactic treatment of eyes with retinal tears of lattice-like degeneration with retinal breaks or highly myopic eyes with increasing white with pressure and increasing condensation of the vitreous base.