Progress and Advances in Porous Silica-based Scaffolds for Enhanced Solid-state Hydrogen Storage: A Systematic Literature Review

Hydrogen plays a crucial role in the future energy landscape owing to its high energy density. However, finding an ideal storage material is the key challenge to the success of the hydrogen economy. Various solid-state hydrogen storage materials, such as metal hydrides, have been developed to realize safe, effective, and compact hydrogen storage. However, low kinetics and thermodynamic stability lead to a high working temperature and a low hydrogen sorption rate of the metal hydrides. Using scaffolds made from porous materials like silica to confine the metal hydrides is necessary for better and improved hydrogen storage. Therefore, this article reviews porous silica-based scaffolds as an ideal material for improved hydrogen storage. The outcome showed that confining the metal hydrides using scaffolds based on porous silica significantly increases their storage capacities. It was also found that the structural modifications of the silica-based scaffold into a hollow structure further improved the storage capacity and increased the affinity and confinement ability of the metal hydrides, which prevents the agglomeration of metal particles during the adsorption/desorption process. Hence, the structural modifications of the silica material into a fibrous and hollow material are recommended to be crucial for further enhancing the metal hydride storage capacity.

Guidelines and treatment patterns for primary rhegmatogenous retinal detachments: Expert consensus and survey in Taiwan Retina Society

Rhegmatogenous retinal detachment (RRD) is a significant cause of vision loss and requires appropriate surgical intervention. There are several approaches available, including observation, laser demarcation, pneumatic retinopexy, scleral buckling, and pars plana vitrectomy, which are chosen based on patient condition, surgeon experience, and national health insurance policies. Despite the various options, there is still no consensus on the optimal intervention. To address this, the Taiwan Retina Society assembled an expert committee with 11 experienced retina specialists to review the current evidence and develop a guideline with seven recommendations for managing RRD patients. Additionally, a survey was conducted with six questions to assess treatment patterns in Taiwan, which included input from the expert committee and an open poll at the 2023 Congress of the Taiwan Retina Society. This report provides a comprehensive summary of the current knowledge and expert consensus on the treatment of RRD, discussing the characteristics of current approaches and providing an overview of current treatment patterns in Taiwan. These findings aim to provide ophthalmologists with the best possible treatment for RRD.

Literature- and Experience-Based Consensus for Acute Post-operative Endophthalmitis and Endogenous Endophthalmitis in Taiwan

Clinical practices on acute post-operative and endogenous endophthalmitis (EnE) are highly variable among clinicians due to a lack of up-to-date, high-quality evidential support. An expert consensus is thus much needed. A panel consisting of ten retinal specialists in Taiwan was organized. They evaluated relevant literature and developed key questions regarding acute post-operative and EnE that are cardinal for practice but yet to have conclusive evidence. The panel then attempted to reach consensus on all the key questions accordingly. There were eight key questions proposed and their respective consensus statements were summarized as follows: Gram staining and culture are still the standard procedures for the diagnosis of endophthalmitis. Vitrectomy is recommended to be performed earlier than the timing proposed by the Endophthalmitis Vitrectomy Study (EVS). Routine intracameral antibiotic injection for post-cataract surgery endophthalmitis prophylaxis is not recommended because of potential compounding error hazards and a lack of support from high-quality studies. Routine fundus examination is recommended for all patients with pyogenic liver abscess. In EnE, vitrectomy is recommended if diffused and dense vitritis is present, or if the disease progresses. These consensus statements may work as handy guidance or reference for clinical practices of acute post-operative and EnE.

Unusual Presentation of Acute Hydroxychloroquine Retinopathy

PURPOSE

To report a rare case of cystoid macular edema (CME) as a presentation of acute hydroxychloroquine-related retinal toxicity.

OBSERVATIONS

A 37-year-old female patient visited our ophthalmology department in October 2019 complaining of bilateral blurred vision and metamorphopsia for 3 days. Best-corrected visual acuity (BCVA) was 6/6 in the right eye and 6/7.5 in the left eye under the Snellen E chart. Before presentation, she had taken hydroxychloroquine as a "reproduction-facilitating medication" prior to the in vitro fertilization (IVF) procedures with the daily dose of 200 mg for 1 week in March 2019 and 400 mg for 1 month in September 2019. She also took a combination of several herbal medicine including "Angelica sinensis" for 6 months in this period. On examination, typical signs of hydroxychloroquine maculopathy such as bilateral paracentral retinal pigment epithelium (RPE) change in blue autofluorescence and loss of the paracentral ellipsoid zone in optical coherence tomography ("flying saucer sign") were noted. CME was also found in fluorescein angiography. Her symptoms improved gradually after cessation of hydroxychloroquine and herb medicine without any further treatment. Resolution of bilateral CME was revealed at 16 weeks with final bilateral BCVA 6/6.

CONCLUSIONS AND IMPORTANCE

Although rare, acute hydroxychloroquine maculopathy could occur in patients with concomitant usage of medications that could interfere with P450 enzymes system. Careful acquisition of drug history and serial ophthalmological examinations are advised in using hydroxychloroquine for disease management even for a short period of time.

Morphological changes of foveal cysts as a predictor for visual response to anti-vascular endothelial growth factor treatments in diabetic macular edema : Degenerative cyst in DME

PURPOSE

To investigate morphological changes of intraretinal cyst in association with visual acuity following treatment for diabetic macular edema.

METHODS

This retrospective study enrolled 105 eyes from 105 treatment naïve patients with diabetic macular edema following anti-vascular endothelial growth factor injections. Best-corrected visual acuity (BCVA) and optical coherence tomography (OCT) data were obtained at baseline, 1, 3, 6, and 12 months. The width and height of the largest intraretinal cyst (IRC) at all different visits were measured and were correlated to final visual acuity by receiver operating characteristic curve. The exudative feature was defined by the presence of hard exudates. Multivariate logistic regression was used to select the independent predictor for visual outcomes.

RESULTS

Intraretinal cyst width but not the cyst height after treatment at 1 month independently predicted final visual loss of ten letters or more (multivariate P = 0.009). The optimal cutoff value was 196 um with a sensitivity of 0.889 and a specificity of 0.656. Eyes with large IRC width using this cutoff were consistently larger than those with small IRC width through 12 months (P = 0.008, Mann-Whitney U test). Small IRC width < 196 um at 1 month was more likely to coexist with exudative feature (P = 0.011, Fisher's exact test). Among baseline factors, large IRC width predicted IRC width ≥ 196 um at 1 month (multivariate P < 0.001).

CONCLUSION

Cyst morphology following intravitreal injection predicts visual outcomes. Eyes with IRC width ≥ 196 um after treatment at 1 month tends to be more degenerative, and less likely to coexist with exudative feature.

STRICT PRO RE NATA VERSUS TREAT-AND-EXTEND REGIMENS IN NEOVASCULAR AGE-RELATED MACULAR DEGENERATION: A SYSTEMATIC REVIEW AND META-ANALYSIS

PURPOSE

To compare the visual and anatomical outcomes between strict pro re nata (strict PRN) and treat-and-extend (T&E) anti-vascular endothelial growth factor (anti-VEGF) regimens for neovascular age-related macular degeneration (nAMD).

METHODS

A meta-analysis of 1-year and 2-year changes between strict PRN and T&E anti-VEGF regimens were conducted in both randomized controlled trials (RCTs) and real-world studies (RWSs). The best-corrected visual acuity (BCVA), central retinal thickness (CRT), and weighted mean numbers of visits and injections were evaluated.

RESULTS

A total of 19 RCTs and 23 RWSs (2,530 eyes in strict PRN and 4,399 eyes in T&E) were included. Mean BCVA change in strict PRN group in both 1-year and 2-year (5.95 and 5.78, respectively) was noninferior to the T&E group (7.85 and 5.96, respectively). Mean CRT changes were also similar in both strict PRN and T&E groups. Mean number of visits were significantly more in the strict PRN group, whereas mean number of injections was significantly more in the T&E group.

CONCLUSION

The strict PRN regimen demonstrates a noninferior BCVA improvement to the T&E regimen, achieving fewer injections, and may be both economically and medically beneficial. Both selections should be provided to patients with an overall consideration.

Synergic Effect of Intravitreal Bevacizumab and Systemic Corticosteroid in Treating Systemic Inflammatory Response Syndrome (SIRS) Associated Purtscher-like Retinopathy

PURPOSE

To demonstrate the treatment effect of combined intravitreal bevacizumab (IVB) and systemic steroid for systemic inflammatory response syndrome (SIRS)-related Purtscher-like retinopathy (PuR).

METHODS

Retrospective case report.

RESULTS

A 19-year-old patient experienced bilateral blurred vision after urinary tract infection-induced SIRS. Typical bilateral PuR was found in fundus examination and fluorescein angiography. Optical coherence tomography (OCT) revealed severe cystoid macular edema (CME) and OCT angiography revealed marked vascular defects in both superficial and deep plexuses. Intravitreal injection of bevacizumab 1.25 mg was first performed in the right eye along with systemic corticosteroid therapy. One week later, marked improvement in visual acuity and CME was noted in the right eye, but not in the non-IVB-treated left eye. IVB was then performed in the left eye and achieved much improvement 8 days later.

CONCLUSION

This report clearly demonstrated the synergic effect of IVB and systemic steroids for CME on SIRS-related PuR.

Baseline characteristics and treatment response predictive of nAMD outcomes with ranibizumab therapy in treatment-naive patients: the RACER subgroup analysis

BACKGROUND

The Ranibizumab AMD Clinical Efficacy Study (RACER) conducted in treatment-naive adult Taiwanese patients with neovascular age-related macular degeneration (nAMD) suggested the importance of early and intensive dosing of ranibizumab for optimal treatment outcomes. This subgroup analysis aims to provide clinical information on treatment response that can potentially guide on maintaining the treatment or switching anti-VEGF agents in the real-world setting.

METHODS

Visual acuity (VA) and central retinal thickness (CRT) were assessed in the RACER subgroup population. Subgroup analysis sets were categorised based on: (1) baseline best-corrected VA (BCVA; ≤ 48 and > 48 letters); (2) baseline CRT (≤ 325 or > 325 μm); and (3) treatment response after three monthly initial injections: < or ≥ 5-letter gain in BCVA and reduction of < or ≥ 50 μm in CRT.

RESULTS

Patient age, sex, nAMD duration and number of ranibizumab injections did not differ significantly between the treatment subgroups. Poor baseline BCVA (≤ 48 letters) and baseline CRT severity (> 325 µm) were predictors of maximum BCVA gains (9.6 ± 12.9 letters [95%CI: 6.3 to 12.9] and 5.1 ± 18.3 letters [95%CI: - 0.5 to 10.8] at Months 3 and 12, respectively) and better CRT reductions (- 127.6 ± 104.2 µm and - 104.2 ± 107.4 µm at Months 3 and 12, respectively; both P < 0.001). For the subgroup showing favourable treatment improvement with BCVA gains ≥ 5 letters after three monthly initial injections, 75.6% of patients maintained follow-up at Month 12 with a mean of 6.5 ± 14.3 letter gains (95% CI: 1.2 to 11.7). The BCVA gains < 5-letter subgroup nevertheless had stable BCVA (0.4 ± 12.1 letter gains) and CRT (- 41.9 ± 61.2 µm) at Month 12, respectively. In the subgroup with ≥ 50 µm CRT reduction after three monthly initial injections, there are significantly higher BCVA improvements vs. the < 50 µm CRT reduction subgroup at Month 3 (5.0 ± 8.6 letter gains vs. 1.5 ± 11.6 letter gains, respectively; intergroup P = 0.005).

CONCLUSION

Lower baseline BCVA and higher baseline CRT were associated with BCVA gains and CRT reductions throughout the 12-month study period. Early CRT improvements after three monthly initial injections were associated with BCVA gains as early as Month 3.

Step-wise diagnostic approach for patients with uveitis - Experts consensus in Taiwan

Uveitis is a sight-threatening disease that can be associated with many different etiologies. Successful treatment of uveitis relies on accurate diagnosis and prompt efficient therapy. History taking, physical and ocular examinations, systemic evaluations, and response to treatment provide crucial information to differentiate possible etiologies involved in the pathophysiology of intraocular inflammation. This article provides recommendations for a step-wise approach to patients with uveitis in Taiwan based on an expert meeting and consensus. Systemic evaluations for uveitis should be performed step-by-step and include investigation of patients' general systemic conditions, ruling out infectious etiologies, and obtaining evidential biomarkers to diagnose a specific disease entity.

Optimal approaches and criteria to treat-and-extend regimen implementation for Neovascular age-related macular degeneration: experts consensus in Taiwan

The management of neovascular age-related macular degeneration (nAMD) has taken a major stride forward with the advent of anti-VEGF agents. The treat-and-extend (T&E) approach is a refined management strategy, tailoring to the individual patient’s disease course and treatment outcome. To provide guidance to implementing anti-VEGF T&E regimens for nAMD in resource-limited health care systems, an advisory board was held to discuss and generate expert consensus, based on local and international guidelines, current evidence, as well as local experience and reimbursement policies. In the experts’ opinion, treatment of nAMD should aim to maximize and maintain visual acuity benefits while minimizing treatment burden. Based on current evidence, treatment could be initiated with 3 consecutive monthly injections. After the initial period, treatment interval may be extended by 2 or 4 weeks each time for the qualified patients (i.e. no BCVA loss ≥5 ETDRS letters and dry retina), and a maximum interval of 16 weeks is permitted. For patients meeting the shortening criteria (i.e. any increased fluid with BCVA loss ≥5 ETDRS letters, or presence of new macular hemorrhage or new neovascularization), the treatment interval should be reduced by 2 or 4 weeks each time, with a minimal interval of 4 weeks. Discontinuation of anti-VEGF may be considered for those who have received 2–3 consecutive injections spaced 16 weeks apart and present with stable disease. For these individuals, regular monitoring (e.g. 3–4 months) is recommended and monthly injections should be reinstated upon signs of disease recurrence.

Peripapillary choroidal neovascularization associated with optic nerve sheath meningioma

Peripapillary choroidal neovascularization (PPCNV), a rare presentation of optic nerve sheath meningioma (ONSM), is associated with various ocular pathologies. Herein, we report a case with characteristics of age-related macular degeneration, PPCNV, optic disc edema, and a retinal–choroidal venous collateral. In addition to the recognition of an orbital base ONSM, magnetic resonance imaging revealed a distended perioptic subarachnoid space with the accumulation of cerebrospinal fluid anterior to the tumor. On the basis of these clinical findings, we postulated the pathogenesis of PPCNV-associated ONSMs.

Management of neovascular age-related macular degeneration: Taiwan expert consensus

Neovascular age-related macular degeneration (nAMD) is a leading cause of irreversible vision loss. The present consensus provides suggestions on diagnosis, evaluation, treatment, and follow-up strategies for nAMD from a panel of 11 practicing ophthalmologists. The experts suggest that the baseline visit for nAMD management should include a comprehensive ophthalmologic examination via a multimodal approach consisting of visual and anatomical evaluation. Patients diagnosed with nAMD should be subjected to treatment with the goal of maintaining visual function while diminishing anatomical disease activity and minimizing treatment burden. Currently, anti-VEGF therapy is the main treatment strategy for nAMD, and evaluation involving comprehensive ophthalmologic examination within 1 month of completion of the loading phase comprising three monthly injections is recommended to guide subsequent management. Either a treat-and-extend or pro re nata regimen can be considered for the maintenance phase of anti-VEGF therapy, and the regimen should be chosen and adjusted according to disease activity, reimbursement criteria, financial burden, and patient preferences. In the event of inactive nAMD or poor treatment outcomes, after thorough evaluation and patient education, anti-VEGF therapy may be stopped. The consensus provides practical nAMD management guidelines for ophthalmologists and fellow healthcare professionals.

Patterns of ellipsoid zone change associated with visual outcome for diabetic macular oedema

Clinical relevance: Optical coherence tomography biomarkers are dynamic and possibly change over time. The dynamic biomarkers may better predict improvement of final vision than those at baseline for diabetic macular oedema after treatment.Background: To investigate predictors for ellipsoid zone (EZ) dynamics and the association with visual acuity after treatment for diabetic macular oedemaMethods: A total of 135 eyes from 135 patients with anti-vascular endothelial growth factor treatment for diabetic macular oedema were retrospectively enrolled in this study. EZ status was evaluated by optical coherence tomography at baseline, 1, 3, 6, and 12 months post-operatively. Macular perfusion status was analysed by fluorescein angiography. Duration of EZ disruption was quantified by giving scores from 0 to 5 based on the sum of visits with evidence of EZ disruption. Linear regression models were used to predict factors for scores of EZ disruption. Binary logistic regression was used to predict various EZ biomarkers for final visual acuity improvement.Results: Thirty of 87 eyes (34.4%) with intact EZ at baseline developed subsequent EZ disruption. For those with EZ disruption at baseline, 17 of 48 (35.4%) patients had restoration of disrupted EZ over time. Non-perfused macula was associated with both earlier development of EZ disruption and poor restoration (p < 0.001 and p = 0.011, respectively). Non-perfused macula, absence of epiretinal membrane, and EZ disruption at baseline predicted higher EZ scores (p < 0.001, p = 0.022 and p < 0.001, respectively). Higher EZ scores (p = 0.016), but not baseline EZ disruption (p = 0.56), were less likely to have improvement of final vision 5 letters or more.Conclusion: Macular perfusion status played an independent role in EZ dynamics. Duration of EZ disruption could be more predictive than baseline status for improvement of vision over 12 months.

Intravitreal Aflibercept versus Ranibizumab for Diabetic Macular Edema in a Taiwanese Health Service Setting

Purpose: To compare the visual and anatomical outcomes between intravitreal aflibercept and ranibizumab for diabetic macular edemaMethods: A total of 194 eyes from 194 patients (aflibercept n = 95, ranibizumab n = 99) were retrospectively enrolled in the study. All eyes fulfilled the key criteria including a baseline best-corrected visual acuity (BCVA) between 20 and 70 ETDRS letters, a central subfield thickness (CST) 300 µm or more. Primary outcomes were BCVA and CST at 1, 3, 6, and 12 months. Maintenance of vision was defined as visual loss of less than 5 letters over 6 to 12 months. Predictors for final visual acuity and visual maintenance were analyzed using multivariate regression models.Results: Both agents achieved comparable visual and anatomical outcomes at any time point over the course of follow-up (all p > .05). At 12 months, aflibercept group had higher proportions of visual gains 5, 10 and 15 letters or more (p = .014, p = .011, and p = .034, respectively). The mean number of injections was 5.0 ± 1.9 in ranibizumab group and 4.5 ± 1.9 in aflibercept group (p = .09). Ranibizumab predicted poor maintenance of vision (p = .009), but not the final visual acuity (univariate p = .1). Ranibizumab was more likely to have recurrence of subretinal fluid than aflibercept in 12 months after resolution of subretinal fluid at baseline (p = .016). Both aflibercept and ranibizumab had similar rates of loss to follow-up (p = .47) and occurrence of vitreous hemorrhage (p = .21).Conclusion: While both agents improved vision with resolution of edema, aflibercept maintained vision more effectively with less recurrence of subretinal fluid at 12 months in real-world settings.

Comparison of visual outcomes between therapy choices and subtypes of polypoidal choroidal vasculopathy (PCV) in Taiwan: a real-world study

Polypoidal choroidal vasculopathy (PCV) is a distinctive type of neovascular age-related macular degeneration prevalent in many Asian countries. However, there is still some controversy in how the subtypes of PCV are classified. This post-hoc study redefined the branching vascular network (BVN) and PCV subtypes through retrospective review of indocyanine green angiography (ICGA) and fluorescein angiography images from two observational studies (RENOWNED/REAL). Of the visual outcomes for each angiographic subtype and treatment pattern investigated, BVN was identified in 56.3% of PCV patients. The proportions and features of the re-defined PCV subtypes were 43.8%, 10.4%, and 45.8% for subtype A (without distinctive features of BVN), B (with BVN but no leakage), and C (with BVN and leakage), respectively. Subtype A had better visual outcomes when compared to subtype C. This possibly resulted from a better baseline visual acuity in subtype A. Moreover, combination therapy [photodynamic therapy plus anti-vascular endothelial growth factor (VEGF)] may lead to better visual improvement than mono-anti-VEGF treatment alone. This study provides the prevalence of PCV subtypes in Taiwan and may serve as a reference for PCV treatment strategies in a real-world setting, especially for the combination therapy and patients without distinctive features of BVN.

Simultaneous existence of three intraocular lens inside one eye

The purpose of the study was to report an unusual case of recurrent pseudophakic cystoid macular edema (PCME) in an eye with three simultaneous intraocular lenses (IOLs) inside. A 57-year-old female with diabetes mellitus (DM) and a history of complicated cataract surgery was diagnosed with cystoid macular edema (CME). Upon examination, an anterior chamber intraocular lens (ACIOL) with vitreous strand in her right eye was noted. The fluorescence angiography revealed CME of the right eye and microaneurysms in both eyes. Pars plana vitrectomy was performed to release the vitreous prolapse and traction around the ACIOL. During the surgery, two sunken posterior chamber IOLs in the vitreous were incidentally found and removed. The vitreous traction strand around the inappropriately placed anterior chamber ACIOL was also released. It was rarely reported that two dislocated IOL and ACIOL simultaneously existed in the same eye. Chronic recurrent PCME in this patient was possibly associated with posteriorly dislocated IOL, DM, and vitreous traction.

Management of diabetic macular edema: experts' consensus in Taiwan

Diabetic macular edema (DME) is the most common cause of vision loss among patients with diabetes mellitus (DM), rendering it an important growing challenge in ophthalmology. In the past decades, the management strategies for DME had a few paradigm shifts, and the advent of an expanding number of anti-vascular endothelial growth factor (VEGF) agents also calls for an in-depth examination of the currently available evidence. This article was composed with the intention to provide recommendations for practicing clinicians to improve the management and, through it the outcomes of DME. Drawing from current guideline recommendations, clinical trial findings and local clinical experiences, these consensus recommendations for the management of DME were formed by an expert panel through iterations of discussion and voting. First, the treatment goal of DME is to achieve best visual outcome with edema improvement while minimizing treatment burden. Second, anti-VEGF therapy should be considered as the first-line treatment for patients with center-involving DME causing vision loss. Baseline visual acuity (VA) and central subfield thickness (CST) should be taken into consideration when choosing anti-VEGF agents. Third, early intensive anti-VEGF therapy (at least 3 monthly doses) is important for better patients' VA and anatomical improvement. In non-responders who have already been treated with 3-5 injections of anti-VEGF agents, it is reasonable to switch to other modalities, such as steroids. Finally, for the follow-up phase, fixed or individualized dosing should be considered based on VA and OCT.

Using optical coherence tomography angiography in assessment of the anti-vascular endothelial growth factor effect for pathological vascular tissue in age-related macular degeneration and polypoidal choroidal vasculopathy

PURPOSE

Using optical coherence tomography angiography to assess and compare changes in pathological vascular tissue, including choroidal neovascularization in neovascular age-related macular degeneration and polypoidal complex in polypoidal choroidal vasculopathy, after treatment with anti-vascular endothelial growth factor.

METHODS

This is a retrospective observational case series study. Clinical data were collected, including that on the best-corrected visual acuity and images of spectrum domain optical coherence tomography and optical coherence tomography angiography of consecutive patients with macula-involved lesions, active pathological vascular tissue in neovascular age-related macular degeneration, and polypoidal complex in polypoidal choroidal vasculopathy who were treated with anti-vascular endothelial growth factor injection. The primary outcome measures were the lesion area, flow density, and flow area of the pathological vascular tissue obtained in optical coherence tomography angiography before treatment, as well as week-1 (W1) and week-5 (W5) after treatment. The secondary outcome measures were the best-corrected visual acuity and the anatomic changes in spectrum domain optical coherence tomography at the same periods.

RESULTS

A total of 86 eyes in 79 patients (mean age: 73.10 ± 10.10 (range = 50-91) years, 45 males (57%), of which two eyes were treatment-naïve) underwent one section of intravitreal treatment. Of which 44 eyes (40 patients) were diagnosed as typical neovascular age-related macular degeneration and 42 eyes (39 patients) as polypoidal choroidal vasculopathy. The sensitivity for detecting choroidal neovascularization in neovascular age-related macular degeneration and polypoidal complex in polypoidal choroidal vasculopathy was 75.00% (33/44) and 69.05% (29/42), respectively. There was no significant difference in the detection rate between neovascular age-related macular degeneration and polypoidal choroidal vasculopathy (p = 0.54). In the detectable group, there were significant decrease in lesion area and flow area in the optical coherence tomography angiography images after anti-vascular endothelial growth factor treatment in both the neovascular age-related macular degeneration group (lesion area: W1 = -26.94 ± 19.50%, W5 = -35.52 ± 30.85%, all ps < 0.001; flow area: W1 = -26.22 ± 25.23%, W5 = -32.24 ± 32.07%, all ps < 0.001) and the polypoidal choroidal vasculopathy group (lesion area: W1 = -25.19 ± 20.27%, W5 = -31.55 ± 27.04%, all ps < 0.001; flow area: W1 = -21.83 ± 26.29%, W5 = -28.31 ± 30.72%, all ps < 0.001). The central subfield retinal thickness in spectrum domain optical coherence tomography also showed similar amelioration in both groups. However, the flow density in optical coherence tomography angiography image and the visual outcome did not reveal any significant difference before or after intravitreal injections, and neither were there significant differences between the neovascular age-related macular degeneration and polypoidal choroidal vasculopathy groups. Concerning the effect on the optical coherence tomography angiography images of pathological vascular tissue, there were no statistical differences among different anti-vascular endothelial growth factor agents (i.e. aflibercept, ranibizumab, and bevacizumab).

CONCLUSION

Our study revealed that optical coherence tomography angiography can be used noninvasively and quantitatively to assess the detailed pathologic vascular structures in both neovascular age-related macular degeneration and polypoidal choroidal vasculopathy. Our study also demonstrated that anti-vascular endothelial growth factor could effectively decrease the lesion size and flow area of both the choroidal neovascularization in neovascular age-related macular degeneration cases and the polypoidal complex in polypoidal choroidal vasculopathy cases; the effects were similar in both diseases.

Acute zonal occult outer retinopathy presenting as optic neuritis

Acute zonal occult outer retinopathy (AZOOR) is an outer retinal disorder characterized by the acute loss of visual functions. Herein, we report a case of AZOOR presenting features mimicking optic neuritis. A 17-year-old healthy male reported fogginess in the right eye for 2 weeks. His best-corrected visual acuity was 20/20 in both eyes. Results of a color vision test and pupillary reaction were unremarkable. Funduscopic examination revealed a subtle hyperemic disc surrounded by hyperpigmentation in the right eye. Visual field examination confirmed an enlarged blind spot in the affected eye. Fundus autofluorescence imaging revealed zonal hyperautofluorescence around the optic disc. Fluorescein angiography showed optic disc staining and a window defect in the retinal pigment epithelium. Optical coherence tomography demonstrated loss of the ellipsoid line at the corresponding hyperautofluorescent region. All these characteristics indicated a diagnosis of AZOOR. However, the prolonged P100 wave observed through visual-evoked potential examination, hyperintensity T2 signal at the retrobulbar optic nerve through magnetic resonance imaging, and mild hyperemic optic disc along with optic disc staining through fluorescein angiography resemble the characteristics of optic neuritis. Because the clinical features of AZOOR are similar to those of optic neuritis, ophthalmologists should be able to differentiate between these two diseases to achieve a timely and correct diagnosis.

Association of Body Fluid Expansion With Optical Coherence Tomography Measurements in Diabetic Retinopathy and Diabetic Macular Edema

Purpose

To evaluate associations of body fluid status with optical coherence tomography measurements in patients with diabetic retinopathy (DR).

Methods

This prospective, cross-sectional study enrolled a total of 104 eyes from 104 patients with diabetes mellitus for fundus evaluations of DR and optical coherence tomography examinations. DR severity was graded via fundus photography. Systemic body fluid status was recorded via a body composition monitor with output values of total body water, extracellular water (ECW), intracellular water, and overhydration (OH). Relative overhydration (ROH) was defined as OH/ECW. Volume overload was defined as ROH ≥7%. Correlations of central subfield thickness (CST) with body fluid status were analyzed by partial correlation with adjustment for age, sex, and body mass index (BMI). Logistic regression analysis was used to evaluate factors associated with diabetic macular edema (DME).

Results

Higher levels of ECW, OH, and ROH were correlated with thick CST in patients with DR (P = 0.006, 0.021, and 0.008, respectively), but not in those without any DR (all P > 0.05), after adjusting for age, sex, and BMI. Patients with DME (n = 31) had higher OH than DR patients without DME (n = 28) or those without any DR (n = 45) (P = 0.002 and P < 0.001, respectively). Multiple regression model showed that volume overload was the independent factor for the presence of DME (odds ratio, 9.532; 95% confidence interval, 2.898-31.348; P < 0.001).

Conclusions

While both ECW and OH reflect CST in patients with DR, overhydration had particularly strong associations with DME. This study provides a novel insight into our current understanding regarding the pathogenesis for DME.

Optical Coherence Tomography Angiography for Assessment of the 3-Dimensional Structures of Polypoidal Choroidal Vasculopathy

Importance

Investigating the quantitative 3-dimensional (3-D) anatomy of polypoidal complex is important for a better understanding of the pathogenesis of polypoidal choroidal vasculopathy (PCV).

Objective

To quantitatively evaluate the 3-D characteristics of polypoidal structures, branching vascular networks (BVNs), and origin of PCV using optical coherence tomography angiography (OCTA) and multiple image systems.

Design, Setting, and Participants

A prospective, observational study was conducted in 47 consecutive Taiwanese patients (47 eyes) from May 21, 2015, to April 30, 2017. All participants were scanned with the Optovue-RTVue-XR-Avanti OCTA system. Patients in whom PCV was identified on OCTA were examined to define characteristics and structures of the original spouting vessels (stalks) from the choroid, polypoidal structures, and BVNs on OCTA.

Main Outcomes and Measures

Quantitative analysis of 3-D structures of the polypoidal complex.

Results

Among the 47 patients, the mean (SD) patient age was 68.9 (8.0) years, and 28 (59.6%) men were included. Clear images of polypoidal structures could be detected in 17 eyes (36.2%, 22 polypoidal structures), BVNs in 26 eyes (55.3%, 26 tufts of BVNs), and stalks of origin from the choroid in 26 eyes (55.3%, 26 stalks) on the en face plane on OCTA. All polypoidal structures were found at a mean (SD) height of 45.3 (36.1) μm above the retinal pigment epithelium (RPE) reference plane that was preset by the machine, while the BVNs were found at a mean (SD) depth of 28.6 (14.2) μm below the RPE reference plane and the choroidal stalks at 80.4 (24.4) μm below RPE reference plane. The mean (SD) thickness of polypoidal structures was 38.4 (15.5) μm and of BVNs, 60.2 (25.0) μm. The polypoidal structures were all above the Bruch membrane within the dome of the RPE detachment, the choroidal stalks were all in the choroid layer. The BVNs could be either above (up to 18 μm), within, or below (up to 28 μm) the Bruch membrane and were in proximity to the double layers of flattened RPE detachment.

Conclusions and Relevance

These results demonstrate a 3-D architecture of PCV that may be helpful for a better understanding of the anatomy, pathophysiology, and pathogenesis of PCV.

Treatment patterns in diabetic macular edema in Taiwan: a retrospective chart review

Objectives

To characterize diabetic macular edema (DME) treatment patterns in Taiwan and examine their impact on health care resource utilization and visual and anatomic outcomes.

Methods

Retrospective, observational cohort study of longitudinal data from medical records of five hospital ophthalmology clinics. Patients with type 2 diabetes and DME who received ≥1 laser treatment or pharmacotherapy (intravitreal/subtenon corticosteroids and/or intravitreal anti-vascular endothelial growth factor [VEGF] agents) between January 2012 and December 2013 (index period) and attended ≥1 follow-up visit after the first treatment during that period were identified (prevalent population, N=431). In addition, a subset that received no anti-VEGFs before 2012 (anti-VEGF-naïve population, N=77) was analyzed. Outcome measures were change in DME treatment distribution between January 2009 and December 2014 and health care resource utilization over up to 3 years from the first DME treatment received in the index period (prevalent population), mean number of anti-VEGF injections and change from baseline in visual acuity and central macular thickness over 12 months (anti-VEGF-naïve population).

Results

Between 2009 and 2014, laser treatment use declined, overall use of anti-VEGFs increased, and bevacizumab use decreased proportionately as ranibizumab use increased. Patients receiving corticosteroids and anti-VEGFs in the first 6 months post-index had greater health care resource utilization than those treated with laser, corticosteroids, or anti-VEGF alone (P<0.0001, cross-cohort comparison). Among anti-VEGF-naïve patients, 69% received one to four anti-VEGF injections in the first year post-index. Overall, visual acuity improvement from baseline was minimal at 1 year (0.4 letters, observed data; 0.1 letters, last observation carried forward), and modest central macular thickness reduction (28 µm [last observation carried forward]) was detected.

Conclusion

In Taiwanese clinics, DME treatment patterns have shifted from use of laser to anti-VEGFs (with higher health care resource utilization); however, few patients receive anti-VEGF injections at the frequency reported in landmark trials, consistent with poorer visual outcomes. Effective alternative treatments with lower treatment burden should be considered.

One-year real-world outcomes of ranibizumab 0.5 mg treatment in Taiwanese patients with polypoidal choroidal vasculopathy: a subgroup analysis of the REAL study

AIM

To assess the effectiveness and safety of ranibizumab 0.5 mg in Taiwanese patients with polypoidal choroidal vasculopathy (PCV) by performing a retrospective exploratory subgroup analysis of the REAL study.

METHODS

REAL was a 12-month, observational, prospective, non-interventional phase IV post-marketing surveillance study conducted at 9 centers in Taiwan. The study collected data as part of the routine patient visits from the medical records of patients with neovascular age-related macular degeneration treated with ranibizumab 0.5 mg according to local standard medical practice and local label and/or reimbursement guidelines. The presence of PCV at baseline was determined using indocyanine green angiography.

RESULTS

At baseline, PCV was diagnosed in 64 of the 303 enrolled patients (21.1%). Of these, 41 patients (64.1%) had received prior treatment; 15 (23.4%) patients had received ranibizumab. The intent-to-treat population included 58 patients; 47 (80%) who received ranibizumab and 11 (20%) who received ranibizumab plus photodynamic therapy (PDT; 9 patients received once, 2 patients received twice). Bevacizumab was used as a concomitant medication in a similar percentage of patients who received ranibizumab (43%, n=20) or ranibizumab plus PDT (45%, n=5). In patients who received ranibizumab, visual acuity (VA) at baseline was 50.1±12.9 Early Treatment Diabetic Retinopathy Study letters, and the gain at month 12 was 1.1±17.8 letters. In patients who received ranibizumab plus PDT, VA at baseline was 51.4±15.9 letters, and there was a marked gain in VA at month 12 (14.0±9.2 letters, P=0.0009). In the intent-to-treat population, the reduction in central retinal subfield thickness from baseline at month 12 was 69.6±122.6 µm (baseline: 310.8±109.8 µm, P=0.0004). The safety results were consistent with the well-characterized safety profile of ranibizumab.

CONCLUSION

In real-world settings, ranibizumab 0.5 mg treatment for 12mo results in maintenance of VA and reduction in central retinal subfield thickness in Taiwanese patients with PCV. Improvements in VA are observed in patients who received ranibizumab plus PDT. There are no new safety findings.

Amalric triangular sign in a case of central retinal artery occlusion combined with posterior ciliary artery occlusion - Case report

Purpose

Amalric triangular sign is a rare phenomenon indicating choroidal ischemia. In this study, we reported a typical Amalric triangular sign in a case of central retinal artery occlusion (CRAO) combined with posterior ciliary artery (PCA) occlusion.

Observations

A 49-year-old women developed sudden visual loss in her left eye for one day. Ocular examination revealed rubeosis iridis, macular retinal edema followed by multiple whitish triangular patches in the peripheral four days later. Fluorescein angiography (FAG) revealed delayed choroidal filling time, delayed arteriovenous transit time, choroidal non-perfusion areas and triangular lesions of hyperfluorescent corresponding to the hypopigmented patches on the fundus. Carotid Doppler and magnetic resonance angiography (MRA) then disclosed 90% stenosis of left internal carotid artery (ICA), causing ischemia of the central retinal artery and posterior ciliary artery.

Conclusions and importance

The Amalric triangular sign indicates the occlusion on the main truck of PCA. The sign might combine with CRAO or branch retinal artery occlusion (BRAO) as presented in our case and therefore is a strong indication of possible systemic vascular risk.

High-quality thulium iron garnet films with tunable perpendicular magnetic anisotropy by off-axis sputtering - correlation between magnetic properties and film strain

Thulium iron garnet (TmIG) films with perpendicular magnetic anisotropy (PMA) were grown on gadolinium gallium garnet (GGG) (111) substrates by off-axis sputtering. High-resolution synchrotron radiation X-ray diffraction studies and spherical aberration-corrected scanning transmission electron microscope (Cs-corrected STEM) images showed the excellent crystallinity of the films and their sharp interface with GGG. Damping constant of TmIG thin film was determined to be 0.0133 by frequency-dependent ferromagnetic resonance (FMR) measurements. The saturation magnetization (Ms) and the coercive field (Hc) were obtained systematically as a function of the longitudinal distance (L) between the sputtering target and the substrate. A 170% enhancement of PMA field (H⊥) was achieved by tuning the film composition to increase the tensile strain. Moreover, current-induced magnetization switching on a Pt/TmIG structure was demonstrated with an ultra-low critical current density (jc) of 2.5 × 106 A/cm2, an order of magnitude smaller than the previously reported value. We were able to tune Ms, Hc and H⊥ to obtain an ultra-low jc of switching the magnetization, showing the great potential of sputtered TmIG films for spintronics.

Metallic Nanoislands on Graphene for Monitoring Swallowing Activity in Head and Neck Cancer Patients

There is a need to monitor patients with cancer of the head and neck postradiation therapy, as diminished swallowing activity can result in disuse atrophy and fibrosis of the swallowing muscles. This paper describes a flexible strain sensor comprising palladium nanoislands on single-layer graphene. These piezoresistive sensors were tested on 14 disease-free head and neck cancer patients with various levels of swallowing function: from nondysphagic to severely dysphagic. The patch-like devices detected differences in (1) the consistencies of food boluses when swallowed and (2) dysphagic and nondysphagic swallows. When surface electromyography (sEMG) is obtained simultaneously with strain data, it is also possible to differentiate swallowing vs nonswallowing events. The plots of resistance vs time are correlated to specific events recorded by video X-ray fluoroscopy. Finally, we developed a machine-learning algorithm to automate the identification of bolus type being swallowed by a healthy subject (86.4%. accuracy). The algorithm was also able to discriminate between swallows of the same bolus from either the healthy subject or a dysphagic patient (94.7% accuracy). Taken together, these results may lead to noninvasive and home-based systems for monitoring of swallowing function and improved quality of life.

Strongly exchange-coupled and surface-state-modulated magnetization dynamics in Bi2Se3/yttrium iron garnet heterostructures

Harnessing the spin–momentum locking of topological surface states in conjunction with magnetic materials is the first step to realize novel topological insulator-based devices. Here, we report strong interfacial coupling in Bi₂Se₃/yttrium iron garnet (YIG) bilayers manifested as large interfacial in-plane magnetic anisotropy (IMA) and enhancement of damping probed by ferromagnetic resonance. The interfacial IMA and damping enhancement reaches a maximum when the Bi₂Se₃ film approaches its two-dimensional limit, indicating that topological surface states play an important role in the magnetization dynamics of YIG. Temperature-dependent ferromagnetic resonance of Bi₂Se₃/YIG reveals signatures of the magnetic proximity effect of T_C as high as 180 K, an emerging low-temperature perpendicular magnetic anisotropy competing the high-temperature IMA, and an increasing exchange effective field of YIG steadily increasing toward low temperature. Our study sheds light on the effects of topological insulators on magnetization dynamics, essential for the development of topological insulator-based spintronic devices.

Understanding the effects of topological insulators on magnetization dynamics of adjacent magnetic materials is essential for novel spintronic devices. Here, Fanchiang et al. report thickness dependence of interfacial in-plane magnetic anisotropy and damping enhancement in Bi₂Se₃/yttrium iron garnet (YIG) bilayers, indicating an important role of topological surface states in the magnetization dynamics of YIG.

Clinical characteristics and visual outcome of macular hemorrhage in pathological myopia with or without choroidal neovascularization

BACKGROUND/PURPOSE

This study aims to evaluate the clinical characteristics and visual outcome of macular hemorrhage in pathological myopia with or without choroidal neovascularization.

METHODS

We conducted a retrospective study of 55 patients with macular coin hemorrhage who were followed for at least 3 months from January 1997 to December 2013 at Shin Kong Wu Ho-Su Memorial Hospital (Taipei, Taiwan). All patients were evaluated using fluorescein angiography and optical coherence tomography for the detection of choroidal neovascularization (CNV). We also recorded clinical characteristics such as age, sex, refractory error, and myopic fundus, to determine the relationship between CNV and non-CNV associated macular hemorrhage.

RESULTS

A total of 55 patients (30 females, 54.55%) were reviewed. The mean age was 39.7 years old. The CNV group was found to be significantly older than the non-CNV group (p < 0.05), and there was no significant difference between sex, visual acuity myopic severity, and the prevalence of fundus findings between CNV and non-CNV groups. Twenty one patients (38.18%) were found to have CNV and were all treated with intravitreal antivascular endothelial growth factor (VEGF). The other 34 patients without CNV were not treated. In both groups, the visual acuity significantly improved (anti-VEGF treated, CNV associated group, 0.7 to 0.39, p = 0.002, and untreated, non-CNV associated group, 0.56 to 0.34, p = 0.0018, respectively).

CONCLUSION

Age significantly correlated to the CNV formation in high myopia with macular hemorrhage. Favorable visual outcomes were found in pathological myopic macular hemorrhage either in the anti-VEGF treated, CNV associated group or in the untreated, non-CNV associated group.

Easy-to-prepare autologous platelet-rich plasma in the treatment of refractory corneal ulcers

As platelets are rich in growth factors for tissue regeneration, autologous platelet-rich plasma (PRP) has been used to treat some refractory corneal defects. Although PRP is effective, the cost of its preparation is very high. This article presents three cases of refractory corneal ulcer under the prescription of autologous PRP. The autologous PRP used in these cases was easily prepared in the blood bank laboratory. In this paper, we collected three patients with refractory corneal ulcer who were unresponsive to conventional treatment. The patients presented with neurotrophic ulcer, exposure corneal ulcer, and limbal deciency with corneal ulcer after hepatitic keratitis. Although we easily prepared autologous PRP eye drops using simple laboratory centrifugation, this preparation still had a clinical effect on corneal defect. The mean intervention time was 24 ± 6.9 days. The case with exposure corneal ulcer had significant wound healing and the other two cases felt subjective symptom relief. There were some clinical improvements of refractory corneal ulcers in our three cases. We present the clinical results of three cases and report an easy procedure for the preparation of autologous PRP. Autologous PRP prepared simply in the laboratory, it may be an alternative option for treating refractory corneal ulcer.

Clinically significant red blood cell antibodies in chronically transfused patients: a survey of Chinese thalassemia major patients and literature review

BACKGROUND

Red blood cell (RBC) alloimmunization is reported to occur at an incidence of 5.2% to 23.5% among patients with thalassemia requiring chronic transfusion. With very limited data on alloimmunization among the Chinese population, a territory-wide study has been performed to look at its prevalence among Chinese thalassemia major patients.

STUDY DESIGN AND METHODS

A retrospective study was conducted by reviewing RBC request records for patients with thalassemia major in Hong Kong from 2006 to 2009. Demographic information and serologic data were retrieved for analysis.

RESULTS

A total of 382 patients were identified and consisted of 190 males and 192 females with a median age of 23 ± 10.4 (range, 0.25 to 52) years. Eighty-eight patients (23.0%) were reported to have RBC antibodies. Of them, 114 alloantibodies, 18 autoantibodies, and 19 unidentified antibodies were identified. Anti-E (42, 39.3%), anti-Mi(a)/Mur (33, 30.85%), anti-c (14, 13.1%), and anti-Jk(a) (seven, 6.55%) were the commonest antibodies reported. However, one case of anti-K (0.9%) and two cases of anti-Fy(b) (1.9%) were reported. Seven of the 18 patients with autoantibodies contained a total of 13 alloantibodies. They were anti-E (five, 38.4%), anti-Mi(a)/Mur (four, 30.8%), anti-Jk(a) (two, 15.4%), anti-c (one, 7.7%), and anti-Fy(b) (one, 7.7%).

CONCLUSION

It is the first comprehensive study on Chinese thalassemia major patients. Clinically significant alloantibodies are different from those observed in the Western population, although antibodies developed against Rh antigens are still common. Chinese patients are less likely to have antibodies against Kell and Duffy blood group antigens, but are more prone to develop antibodies against the Miltenberger antigens.

A combination of intravitreal bevacizumab injection with tunable argon yellow laser photocoagulation as a treatment for adult-onset Coats' disease

PURPOSE

The purpose of this study was to investigate the effectiveness of intravitreal bevacizumab injections combined with tunable argon yellow laser photocoagulation as a treatment for adult-onset Coats' disease.

METHODS

We consecutively treated 3 patients suffering from Coats' disease diagnosed in adulthood with a combination of intravitreal bevacizumab injection and tunable argon yellow laser photocoagulation. All patients received an intravitreal injection of 2.5 mg bevacizumab together with various sessions of laser photocoagulation targeting the area of telangiectasia. The patients' best-corrected visual acuities were recorded. Fundus photography, fluorescein angiography (FA), and optical coherence tomography were used to monitor vascular and retinal exudate changes.

RESULTS

Fundus photography and FA of all 3 patients revealed significant regression of the vascular dilatation and the aneurysmal appearance of the telangiectasia areas. Optical coherence tomography also showed a significant subsidence of the macular edema and submacular fluid in all patients. A concomitant improvement in visual acuity was also noted. No treatment-related complications were identified.

CONCLUSIONS

Combining intravitreal bevacizumab and tunable argon yellow laser photocoagulation is an efficient treatment of choice for Coats' disease that has been diagnosed in adulthood.

Intraocular gas associated pressure-induced interface keratopathy 8 years after laser in situ keratomileusis

The authors report a clinically distinctive form of elevated intraocular pressure-induced interface keratopathy that occurred after a pars plana vitrectomy with intraocular gas tamponade for a macular hole in the right eye in a 35-year-old woman who had laser in situ keratomileusis in both eyes 8 years previously. The intraocular pressure was increased to 37 mm Hg after surgery. Diffuse lamellar keratitis-like interface infiltration was found with concurrent elevated intraocular pressure. The interface infiltration did not respond to steroids but resolved after the intraocular pressure was controlled. This case suggests that interface keratopathy is associated with increased intraocular pressure. Assessment of intraocular pressure is essential in patients presenting with interface keratopathy, especially in those who have undergone posterior segment operations with gas tamponade.

Foster Kennedy Syndrome in a Case with Retinitis Pigmentosa

A 57-year-old woman suffering from long-term visual disturbance due to retinitis pigmentosa noted an even more severe deterioration of her left vision for several months. On ophthalmologic examination, her vision was 1/60 in the right eye and light perception (LP) in the left eye. An RAPD sign was noted in her left eye. Bilateral fundus revealed the typical appearance of severe retinitis pigmentosa. The optic disc of her right eye was markedly swollen, whereas that of the left eye was pale. Under the impression of the Foster Kennedy syndrome, a magnetic resonance imaging (MRI) study was arranged revealing a well-encapsulated round mass with a contrast enhancement of about 4.45 cm in diameter located in the left frontal lobe. The patient might have ignored the visual disturbance in her left eye caused by tumor compression because of her illness of retinitis pigmentosa, which had caused her visual disturbance since childhood.

Quantitative optical coherence tomography findings in a 4-year-old boy with typical morning glory disk anomaly

Morning glory disk anomaly (MGDA) is a congenital malformation of the optic disk that is usually unilateral. It has characteristic fundus findings, including enlarged optic disk opening and funnel-shaped excavation of the peripapillary fundus. Optical coherence tomography (OCT) with micrometer resolution and cross-sectional imaging capabilities can provide detailed information about the structure of the living eye. Some reports have used OCT to demonstrate the structure of the disk in older patients with MGDA but, to our knowledge, no quantitative OCT report concerning a child with MGDA has been published previously.

Validation of a prediction rule for development of rheumatoid arthritis in patients with early undifferentiated arthritis

Objective:

To validate a model which predicts progression from undifferentiated arthritis (UA) to RA, in a Canadian UA cohort.

Methods:

The prediction rule, comprising variables which are scored from 0 to 13, with higher scores reflecting an increased risk of RA, was applied to baseline characteristics of all patients with UA. Progression to RA was determined at 6 months.

Results:

105 patients were identified. By 6 months, 80 (76%) had developed RA while 25 (24%) had developed another diagnosis. Number of tender and swollen joints, rheumatoid factor positivity, anti-cyclic citrullinated peptide positivity, poor functional status and high disease activity were associated with development of RA (p<0.01). Median prediction score was 8.0 for progressors, 5.0 for non-progressors. With these cut-off points, 18 (72%) patients with scores ⩽5 did not develop RA, while 35 (97%) with scores ⩾8 did develop RA.

Conclusions:

High scores in our cohort predicted those who progressed to RA by 6 months. Baseline scores ⩾8 corresponded with higher rates of progression.

Complex temporal patterns of spontaneous initiation and termination of reentry in a loop of cardiac tissue

A two-component model is developed consisting of a discrete loop of cardiac cells that circulates action potentials as well as a pacing mechanism. Physiological properties of cells such as restitutions of refractoriness and of conduction velocity are given via experimentally measured functions. The dynamics of circulating pulses and the pacer's action are regulated by two threshold relations. Patterns of spontaneous initiations and terminations of reentry (SITR) generated by this system are studied through numerical simulations and analytical observations. These patterns can be regular or irregular; causes of irregularities are identified as the threshold bistability (T-bistability) of reentrant circulation and in some cases, also phase-resetting interactions with the pacer.