Treatment of exposed explants with donor sclera and amniotic membrane.
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Adult↗
Biomedical subjects
David Wong
Publications and source records attributed to David Wong.
Early vitrectomy for fundus-obscuring dense vitreous haemorrhage from presumptive retinal tears.
BACKGROUND: Published literature on the management of patients with fundus-obscuring dense vitreous haemorrhage due to presumptive retinal tears is sparse and advocates waiting for spontaneous resolution. Surgery is indicated only when a definite retinal tear or retinal detachment is identified. METHODS: A retrospective review of all patients who underwent early vitrectomy for vitreous haemorrhage associated with posterior vitreous detachment was carried out. A comparison of initial visual acuity versus final visual acuity after vitrectomy was performed. The number of eyes that were found to have retinal tears and retinal detachment were documented. Initial and final Snellen acuities were used for statistical analysis. Categorical data were analysed using Fisher's exact test and statistical significance was considered to be p < 0.05. RESULTS: Sixteen eyes were identified and all these patients presented or were referred soon after the onset of vitreous haemorrhage. Associated ocular pathology (choroidal neovascular membrane, retinal branch vein occlu-sion, macroaneurysm) was suspected to be the source of the haemorrhage in 4 eyes. Vitrectomy was carried out in 12 eyes soon after presentation (mean time 6.3 days, range 1-28 days). Nineteen retinal breaks were seen in these eyes and 5 eyes had more than two breaks. None of the eyes were found to have proliferative vitreoretinopathy at the time of surgery. Two eyes needed repeat surgery for new retinal breaks. Excluding the eyes found to have an ocular pathology as the cause of vitreous haemorrhage, the mean visual acuity improved from hand movements to 6/12 (p < 0.001). CONCLUSIONS: Early vitrectomy for spontaneous dense fundus-obscuring vitreous haemorrhage and posterior vitreous detachment is safe. Since the number of patients in this study was small, a prospective randomised controlled study comparing early versus late vitrectomy is needed to see whether early surgery also prevents proliferative vitreoretinopathy formation.
Aged↗
Positron emission tomography in the detection and staging of ocular adnexal lymphoproliferative disease.
PURPOSE: To evaluate the role of fluorine 18 deoxyglucose positron emission tomography (FDG PET) in the initial staging of ocular adnexal lymphoma (OAL). DESIGN: Retrospective nonrandomized case series. PARTICIPANTS: Eleven patients with OAL who underwent FDG PET at initial staging. METHODS: Retrospective review of all the clinical and imaging records, including computed tomography (CT) and FDG PET. MAIN OUTCOME MEASURES: The ability of PET studies to detect OAL and distant disease was compared with CT. RESULTS: Eleven patients with OAL who underwent FDG PET at initial staging were retrospectively reviewed having full access to their clinical and imaging data. Fluorine 18 deoxyglucose PET found distant disease in 5 of 6 lymphoma patients with systemic disease; 4 of these patients (66%) were upstaged, changing the clinical management. Orbital lesions were demonstrated in 3 of 11 patients, giving PET a sensitivity of 27% in the orbit and 83% systemically for detection of lymphoma. CONCLUSION: The ability of FDG PET to find systemic extranodal lymphomatous sites not detected with conventional imaging provides valuable information in OAL patients, which may result in important changes in staging and management. The technique does have limitations in detecting OAL compared with conventional imaging, possibly owing to background physiologic activity in the extraocular muscles in the orbit and the small volume of some orbital deposits.
Adult↗
Does the surface property of a disposable applanation tonometer account for its underestimation of intraocular pressure when compared with the Goldmann tonometer?
BACKGROUND: Disposable tonometers are increasingly being adopted partly because of concerns over the transmission of variant Creutzfeldt-Jakob disease and partly for convenience. Recently, we have found one such tonometer (Tonojet by Luneau Ophthalmologie, France) underestimated the intraocular pressure (IOP). METHODS: We hypothesized that this underestimation was caused by a difference in the surface property of the tonometers. A tensiometer was used to measure the suction force resulting from interfacial tension between a solution of lignocaine and fluorescein and the tonometers. RESULTS: The results showed that the suction force was significantly greater for the Goldmann compared to the Tonojet. CONCLUSIONS: The magnitude of this force was too small to account for the difference in IOP measurements. The Tonojet was less hydrophilic than the Goldmann, and the contact angle of the fluid was therefore greater. For a given tear film, less hydrophilic tonometers will tend to have thicker mires, and this may lead to underestimation of the IOP. When such disposable tonometers are used, it is recommended care should be taken to reject readings from thick mires.
Diagnostic Errors↗
Sequencing and analysis of 10,967 full-length cDNA clones from Xenopus laevis and Xenopus tropicalis reveals post-tetraploidization transcriptome remodeling.
Sequencing of full-insert clones from full-length cDNA libraries from both Xenopus laevis and Xenopus tropicalis has been ongoing as part of the Xenopus Gene Collection Initiative. Here we present 10,967 full ORF verified cDNA clones (8049 from X. laevis and 2918 from X. tropicalis) as a community resource. Because the genome of X. laevis, but not X. tropicalis, has undergone allotetraploidization, comparison of coding sequences from these two clawed (pipid) frogs provides a unique angle for exploring the molecular evolution of duplicate genes. Within our clone set, we have identified 445 gene trios, each comprised of an allotetraploidization-derived X. laevis gene pair and their shared X. tropicalis ortholog. Pairwise dN/dS, comparisons within trios show strong evidence for purifying selection acting on all three members. However, dN/dS ratios between X. laevis gene pairs are elevated relative to their X. tropicalis ortholog. This difference is highly significant and indicates an overall relaxation of selective pressures on duplicated gene pairs. We have found that the paralogs that have been lost since the tetraploidization event are enriched for several molecular functions, but have found no such enrichment in the extant paralogs. Approximately 14% of the paralogous pairs analyzed here also show differential expression indicative of subfunctionalization.
Animals↗
The effect of problem-based learning on students' approaches to learning in the context of clinical nursing education.
The effect of problem-based learning (PBL) on nursing students' approaches to learning has received scanty attention in nursing education. The purpose of the present study was to evaluate the effect of PBL on students' approaches to learning in clinical nursing education. Using a one-group before-after quasi-experimental design, the revised two-factor Study Process Questionnaire (R-SPQ-2F) was administered to compare students' approaches to learning before and after a period of clinical education in which PBL was implemented. Focus group interviews were used to elicit from students their PBL experience. Of the 237 students who participated in the study, 187 returned the R-SPQ-2F, representing a response rate of 78.9%. Twenty-eight of the students also participated in focus group interviews. The R-SPQ-2F scores indicated that for the deep approach to learning, the post-test mean score was noticeably higher than that at the pre-test (p=0.005). No significant difference was observed between the pre-test and post-test mean scores for the surface approach to learning (p>or=0.05). The four themes inductively derived from students' descriptions of their clinical education experience (motivated to learn; self-direction in learning; active, interactive and student-centred learning; and enjoyment in learning) also suggested that the students adopted a deep approach to learning during a period of clinical education in which PBL was implemented.
Adult↗
Equine herpes myeloencephalopathy in a 12-year-old American quarter horse.
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Acyclovir↗
Endoscopic full-thickness plication for the treatment of gastroesophageal reflux disease: A randomized, sham-controlled trial.
BACKGROUND & AIMS: The aim of this study was to determine the effectiveness of endoscopic full-thickness plication for the treatment of gastroesophageal reflux disease (GERD) in comparison with a sham procedure. METHODS: Patients with symptomatic GERD requiring maintenance proton pump inhibitor (PPI) therapy were entered into a randomized, single-blind, prospective, multicenter trial. Seventy-eight patients were randomly assigned to undergo endoscopic full-thickness restructuring of the gastric cardia with transmural suture. Eighty-one patients underwent a sham procedure. Group assignments were revealed following the 3-month evaluation. The primary end point was > or =50% improvement in GERD health-related quality of life (HRQL) score. Secondary end points included medication use and esophageal acid exposure. RESULTS: By intention-to-treat analysis, at 3 months, the proportion of patients achieving > or =50% improvement in GERD-HRQL score was significantly greater in the active group (56%) compared with the sham group (18.5%; P < .001). Complete cessation of PPI therapy was higher among patients in the active group than in the sham group by intention-to-treat analysis (50% vs 24%; P = .002). The percent reduction in median percent time pH < 4 was significantly improved within the active group versus baseline (7 vs 10, 18%, P < .001) but not in the sham group (10 vs 9, -3%, P = .686). Between-group analysis revealed the active therapy to be superior to the sham in improving median percent time pH < 4 (P = .010). There were no perforations or deaths. CONCLUSIONS: Endoscopic full-thickness plication more effectively reduces GERD symptoms, PPI use, and esophageal acid exposure than a sham procedure.
Endoscopy, Gastrointestinal↗
Clinical recommendations for the use of recombinant human erythropoietin in patients with hepatitis C virus being treated with ribavirin.
Today, combination antiviral therapy with pegylated interferon-alpha and ribavirin (RBV) allows many patients infected with hepatitis C virus (HCV) to achieve a sustained virological response, which is equivalent to cure. Data also support the clinical benefit of combination antiviral therapy in patients coinfected with HCV and HIV, and in patients who have received a liver transplant. Antiviral therapy with pegylated interferon-alpha and RBV is, however, associated with a high incidence and significant magnitude of anemia. This anemia may have several mechanisms, including bone marrow suppression and hemolysis. In addition, patients coinfected with HIV may have both pre-existing and RBV-associated anemia. Management of anemia in patients with HCV through RBV dose reduction or treatment discontinuation may compromise the effectiveness of treatment, because studies have demonstrated that treatment adherence or maintenance of antiviral therapy dose is an important predictor of sustained virological response. Anemia associated with combination antiviral therapy in patients with HCV is frequently associated with an inadequate or blunted endogenous erythropoietin response. Accumulating evidence now supports the use of recombinant human erythropoietin (rHuEpo) to manage anemia in these patients, with the objective of maintaining the RBV dose, but clinical standards are lacking. The present article reviews the data relevant to the use of rHuEpo in this patient population and proposes a set of clinical practice standards to assist clinicians in selecting patients for rHuEpo and in implementing rHuEpo therapy effectively.
Algorithms↗
The presence of AC133-positive cells suggests a possible role of endothelial progenitor cells in the formation of choroidal neovascularization.
PURPOSE: Recent evidence suggests that vasculogenesis as well as angiogenesis occurs throughout the body during neovascularization. The recruitment of circulating stem cells is a key feature of vasculogenesis. The purpose of the present study was to determine whether markers of endothelial progenitor cells (EPCs) are present in choroidal neovascularization (CNV) secondary to age-related macular degeneration (AMD). METHODS: Surgically excised CNV (n = 9) membranes from patients with AMD were probed with immunohistochemical techniques using the following monoclonal antibodies: AC133 a putative marker of EPCs and hematopoietic stem cells (HSCs); the endothelial cells markers CD31, CD34, and von Willebrand factor (vWF); and cytokeratins and CD68, markers for retinal pigment epithelium (RPE) and macrophages, respectively. After secondary antibody amplification, reactions were visualized with fast red substrate. RESULTS: Six of nine specimens demonstrated cells positive for AC133 that were all found within predominantly cellular regions of the specimens. In the avascular fibrous stromal core of all specimens, the predominant cells were RPE cells and macrophages. The peripheral component of all CNV membranes was highly vascular and showed varying immunoreactivity for all endothelial markers. The greatest immunoreactivity for endothelial markers was observed with CD34 and vWF and least for CD31. CONCLUSIONS: These findings support animal studies that vasculogenesis, in addition to angiogenesis, may contribute to the neovascularization that occurs in AMD.
AC133 Antigen↗
Can the sequential use of conventional silicone oil and heavy oil be a strategy for the management of proliferative vitreoretinopathy?
INTRODUCTION: Densiron is a novel long-term tamponade. Its specific gravity is 1.06 g/mL and as such it is heavier than water and provides support for the inferior retina. As proliferative vitreoretinopathy (PVR) has a propensity for the inferior retina, we used Densiron on a consecutive series of 97 cases with inferior pathology. We hypothesised that the sequential use of conventional and heavy silicone oil is a strategy for the management of PVR. MATERIALS AND METHODS: A consecutive interventional case series involving the use of Densiron for PVR cases was studied. Patients were selected if conventional silicone oil and Densiron were used sequentially. Anatomical success was defined as total re-attachment in the absence of any tamponade agent for at least 3 months post oil removal. RESULTS: Of the 97 patients, 10 patients fulfilled the criteria. Surgery involving Densiron was successful in re-attaching the retina in 7 of 10 cases, with one sequence of alternating light then heavy oil operation, and with one further surgery using silicone oil in the remaining 3 cases. The mean LogMAR preoperative vision was 1.57 and the postoperative vision was 0.82. In 8 of 10 patients, the final vision was 20/200 or better; in 5 of 10 patients, 20/80 or better. The mean follow-up was 19.5 months (range, 9 to 45). CONCLUSIONS: The sequential use of conventional silicone oil and Densiron may be a strategy in reducing the number of re-operations. Our case series shows that despite multiple surgical procedures, favourable visual outcome can be achieved.
Adult↗
A mouse atlas of gene expression: large-scale digital gene-expression profiles from precisely defined developing C57BL/6J mouse tissues and cells.
We analyzed 8.55 million LongSAGE tags generated from 72 libraries. Each LongSAGE library was prepared from a different mouse tissue. Analysis of the data revealed extensive overlap with existing gene data sets and evidence for the existence of approximately 24,000 previously undescribed genomic loci. The visual cortex, pancreas, mammary gland, preimplantation embryo, and placenta contain the largest number of differentially expressed transcripts, 25% of which are previously undescribed loci.
Alternative Splicing↗
Design, synthesis and biological evaluation of novel, simplified analogues of laulimalide: modification of the side chain.
Novel, simplified analogues of the microtubule-stabilizing anticancer agent laulimalide, including the first derivatives with unnatural side chains, were designed by molecular modelling, synthesized by a late-stage diversification strategy, and evaluated in vitro for growth inhibition of human ovarian carcinoma cell lines (A2780, A2780/AD10).
Antineoplastic Agents↗
Central and near peripheral retinal contributions to the depth-of-focus using naturalistic stimulation.
Although the depth-of-focus (DOF) has been investigated separately in the central retina and in the near retinal periphery, knowledge about their combined relative contribution to overall blur perception has remained unknown. In the present study, the DOF was measured psychophysically with a naturalistic pictorial stimulus as a function of spatial extent across the near retinal periphery under monocular Badal viewing conditions with accommodation paralyzed. The group mean total DOF progressively increased linearly with target size. Based on the individual DOF responses, the group was categorized into two subgroups: a predominantly centrally-driven and a centrally plus peripherally-driven subgroup. The results implicated partial cone pooling of blur information, as well as influence from perceptual, attentional, and optical aspects. However, the subgroup response profiles suggested individual differences in the weighting of the near peripheral blur information at the retinal level, and perhaps at higher-level areas of the visual system, involving spatial integration and global attentional processing.
Accommodation, Ocular↗
Inhibition by doxycycline of angiogenesis in the chicken chorioallantoic membrane (CAM).
Doxycycline, a tetracycline derivative, has many properties in addition to its antibiotic activity, including inhibition of matrix metalloproteinases (MMPs) and the ability to chelate divalent cations including Ca(2+). It has been shown to inhibit endothelial cell growth in vitro, and reduce the development of experimental tumours, especially bone metastasis in a model of breast cancer. We examined the effects of doxycycline on angiogenesis in the chicken chorioallantoic membrane (CAM) model, and showed that doxycycline will cause loss of the chorionic plexus in CAMs when applied at day 8 of incubation, and the duration of this inhibition was dose-dependent. Repeated doses prolonged the inhibition, but following removal of the doxycycline there was rapid recovery of the chorionic plexus. The effects of doxycycline are in part mimicked by the MMP inhibitor 1,10-phenanthroline, and more closely by the Ca(2+)-chelating agent EGTA. Doxycycline was equally effective in causing loss of the chorionic plexus by day 11 in CAMs, a time at which the blood vessels are established. Doxycycline has important potential as an antiangiogenic treatment. It is capable of inhibiting angiogenesis in an in vivo model, including the removal of comparatively mature endothelial cells. The response is sensitive to the dosing regimen and the effect is rapidly reversible.
Animals↗
Management of traumatic posterior capsular rupture: corneal approach with high speed vitrector.
A 15-year-old boy was referred for reduced left-eye vision 2 weeks after a blunt trauma. The presenting visual acuities were 6/12 in the right eye and counting fingers in the left eye. Examination revealed a white cataract in the left eye with loss of convexity of the anterior lens surface. Ultrasonography confirmed a ruptured posterior capsule. Removal of the lens was approached via a clear corneal cataract incision. After insertion of an anterior chamber maintainer and capsulorhexis was performed, the lens matter was removed with vitreous cutter via the cataract incision, using its cutting and aspirating modes. A foldable intraocular lens (IOL) was inserted in the capsular bag. Visual acuity improved to 6/18 1 month after surgery and further improved to 6/6 at 6 months. The IOL was stable with no decentration or posterior capsule opacification.
Adolescent↗
Time to treatment for women with chlamydial or gonococcal infections: a comparative evaluation of sexually transmitted disease clinics in 3 US cities.
BACKGROUND: Many women with positive screening tests for chlamydia or gonorrhea are not promptly treated and are at risk for complications and further disease transmission. Improved methods for notifying infected patients might increase timely treatment in this population. GOAL: Describe notification procedures at STD clinics in Washington, DC; Los Angeles; and San Diego and compare timeliness of treatment during 2000 to 2002. STUDY: Interviews were conducted to determine methods for notifying infected patients. Data were abstracted from 327 medical records of women with chlamydia or gonorrhea who had not been treated presumptively. The interval between specimen collection and treatment ("time to treatment") was calculated. RESULTS: Each clinic had different procedures for notifying untreated infected women. Among those treated, the median time to treatment was 18 days in Washington, DC, and 8 days in Los Angeles. In San Diego, the median time to treatment was initially 14 days, which improved to 7 days after patient-notification procedures were changed. CONCLUSION: Simple changes in patient notification procedures can decrease time to treatment at STD clinics. STD programs should evaluate time to treatment and institute methods for efficient patient follow-up.
Adult↗
What pressure is exerted on the retina by heavy tamponade agents?
BACKGROUND: Histological changes in the retina during the use of heavy tamponade agents have been linked with the pressure on the retina caused by the increased specific gravity of the agent. This paper calculates the possible increases in pressure due to these agents and questions the validity of this argument. METHODS: A model eye chamber was used to make measurements of the shape of F6H8 bubbles, with incrementally increasing volumes, and thus calculate the maximum possible increase in pressure under the tamponade agent. RESULTS: The maximum increase in pressure under an F6H8 tamponade which completely fills an eye with a diameter of 2.2 cm would be 0.52 mmHg. CONCLUSIONS: This increase in pressure is within normal diurnal pressure changes in the eye; therefore, it would seem unlikely that such an increase could cause the histological changes observed. With increasing volumes of a heavy tamponade agent, aqueous is excluded from a greater area of retina. This could account for the pathological changes reported.
Chemical Phenomena↗