Diagnostic accuracy of 4D flow MRI comparing 2mm3 and 3mm3 spatial resolution

Funding Acknowledgements

Type of funding sources: Public Institution(s). Main funding source(s): National Institute for Health Research, UK University of Leeds

Background

Cardiac magnetic resonance (CMR) examinations requiring repeated breath-holds are challenging in younger patients. While 4-dimensional phase-contrast (4D flow) CMR does not require breath-holds, acquisition has been lengthy. Therefore to date spatial resolution has been influenced mainly by scan length. With accelerated sequences becoming available, higher spatial resolution is becoming clinically feasible.

Purpose

We therefore evaluated the minimum spatial resolution in 4D flow CMR necessary for accurate clinical assessment.

Methods

Ten healthy volunteers (mean age 24.8 years) underwent cardiac examinations on a 3T scanner using a 4D Flow prototype sequence at 2x2x2mm3 (4DFlow2) and 3x3x3mm3 (4DFlow3) spatial resolution. Net forward flow (FF) and peak velocity (PV) using valve tracking were calculated with commercially available software and kinetic energy (KE) in the left ventricle (LV) was analysed using a research tool. Bland-Altman analysis was used for statistical assessment and is reported as bias ± limits of agreement.

Results

Aortic valve flow metrics were similar in 4DFlow2 (FF 94ml; PV 133cm/s) and 4DFlow3 (FF 95ml; PV 130cm/s), and both showed good agreement with 2D PC MRI (FF 93ml, Bland-Altman:1.6 ± 9.7 and 2.2 ± 13.5, respectively). Similar results were obtained for pulmonary valve flow (FF 138cm/s; Bland-Altman:4.7 ± 15.1 and 8.1 ± 18.2, respectively). Branch pulmonary artery (PA) FF showed good agreement with the main PA FF in 2D and 4DFlow2 (Bland-Altman:1.1 ± 15.9 and 1.1 ± 10.6, respectively), but not in 4DFlow3 (Bland-Altman:1.1 ± 32.5). Global LV KE measured by 4DFlow3 was on average 12% lower compared to 4DFlow2, whereas maximum systolic LV KE was similar in both acquisition methods.

Conclusions

3mm3 spatial resolution appears to be sufficient for clinical evaluation of aortic and pulmonary valves. Smaller vessels such as branch pulmonary arteries require higher resolution for accurate assessment. While no gold standard is available for kinetic energy assessment, our results suggest that some parameters LV energetic assessment is spatial resolution sensitive. Differences in SNR might also contribute to the differing results.

Abstract Figure. Bland-Altman plots for 4D flow MRI

Risk Factors for Contact Lens-Related Microbial Keratitis and Associated Vision Loss in a South Indian Population

OBJECTIVES

To identify risk factors associated with contact lens-related microbial keratitis (CL-MK) and subsequent vision loss in a south Indian population.

METHODS

A retrospective study of medical records at the LV Prasad Eye Institute in Hyderabad, India, of patients diagnosed with CL-MK and of controls who had no history of corneal inflammation during contact lens wear was undertaken. Variables such as demographic data, contact lens wear details, duration of the event, visual acuity, epithelial defect and infiltrate size, and microbiology of the cornea during the event were collected. Differences between cases and controls were analyzed using parametric and nonparametric tests. Logistic regression was used to calculate the odds ratio (OR) and associated 95% confidence intervals in univariate and multivariate analyses for cases vs. controls and for factors associated with vision loss.

RESULTS

One hundred sixty-seven cases of CL-MK and 153 controls were included in the analyses. Risk factors associated with the greatest increased OR for CL-related MK were: being in professional employment vs. a student (OR=3.9), disposing lenses yearly versus monthly or biweekly (OR=2.2), and any overnight wear (OR=2.8). Risk factors associated with vision loss were: high myopia (OR=3.6), severe vs. mild severity (OR=16.0), and hypopyon (OR=4.3).

CONCLUSIONS

Identification of these risk factors may help inform safe contact lens wear habits and management strategies.

Sol-Gel Nanocomposite Coatings for Preventing Biofilm Formation on Contact Lens Cases

Purpose

To evaluate the efficacy of a nanosilver-based sol–gel coating in preventing biofilm formation on contact lens cases.

Methods

An organic–inorganic hybrid silica–zirconia sol formulation with immobilized silver nanoparticles was deposited on contact lens case coupons. The coated and uncoated coupons were subjected to biofilm formation to Gram-negative and Gram-positive keratitis isolates and ATCC strains using a standard protocol. The biofilms were evaluated using crystal violet, MTT assay, and scanning electron microscope (SEM) examination. The duration of efficacy of the coating was evaluated by exposing the coated and uncoated coupons to a multipurpose lens cleaning solution for various durations up to 30 days and comparing their biofilm characteristics. The cytotoxicity of the coated surface was assessed using cell culture studies.

Results

Cross-hatch tests and SEM confirmed the presence of a uniform, well-adhered coating on the surface. The coating resulted in a nearly 95% reduction in biofilm formation of the tested bacteria and was effective despite exposures of up to 30 days to a multipurpose lens cleaning solution. The coating did not exhibit cytotoxicity to human corneal epithelial cells.

Conclusions

The silver nanoparticle-based coating exhibits a good antibiofilm property for both Gram-negative bacilli and Gram-positive cocci and is promising for commercial use in preventing contact lens-related infections.

Translational Relevance

Biofilm formation on lens cases continues to be an important concern. The proposed coating will help reduce such formations, thus reducing the risk of lens-associated microbial keratitis.

Response of L V Prasad Eye Institute to COVID-19 outbreak in India: experience at its tertiary eye care centre and adoption to its Eye Health Pyramid

AIM

To summarize the experience of response to COVID-19 outbreak at a tertiary eye care institute and its network of health facilities in India.

METHODS

Our responses are based on the principles of social distancing, hand hygiene, respiratory etiquettes, surface disinfection protocol, and rational use of appropriate personal protective equipment (PPE). We describe our response in terms of administrative controls, clinical protocols, staff protection, environmental controls, and social distancing measures. We also discuss our communication strategies and monitoring systems, to ensure compliance to protocols.

RESULTS

Administrative control is mainly related to formation of task force and its functions. Clinical protocols are related to patient triaging methods and clinical examination guidelines in Outpatient, Inpatient and Operating Room. Staff protection is focused on training staff on the protocols to be followed in hospital as well as at home, and use of PPE. Environmental protocol is focused on cleaning and disinfectant methods to be used in the hospital. In addition, there are systems for communication as well as monitoring compliance to protocols.

CONCLUSION

We hope that these protocols and our experience would help the ophthalmic community globally and serve as a guide to protect ophthalmologists and ophthalmic care personnel, and their patients across the world.

Branched amphotericin functional poly(N-isopropyl acrylamide): an antifungal polymer

Branched poly(N-isopropylacrylamide) was functionalized with Amphotericin B (AmB) at the chain ends to produce an antifungal material. The polymer showed antifungal properties against AmB-sensitive strains of Candida albicans, Fusarium keratoplasticum and Aspergillus flavus (minimal inhibitory concentration ranged from 5 to 500 µg ml^-1) but was not effective against an AmB resistant strain of C. albicans nor against Candida tropicalis. The polymer end groups bound to the AmB target, ergosterol, and the fluorescence spectrum of a dye used as a solvatochromic probe, Nile red, was blue shifted indicating that segments of the polymer became desolvated on binding. The polymer was less toxic to corneal and renal epithelial cells and explanted corneal tissue than the free drug. Also, the polymer did not induce reactive oxygen species release from peripheral blood mononuclear cells, nor did it cause a substantial release of the proinflammatory cytokines, tumour necrosis factor-α and interleukin-1β (at 0.5 mg ml^-1).

Corneal delivery of moxifloxacin and dexamethasone combination using drug-eluting mucoadhesive contact lens to treat ocular infections

The important causes of loss of vision are ocular infections, including keratitis and conjunctivitis. Attaining an adequate concentration of topically applied antibiotics to prevent or treat infections within the cornea is challenging. The study aimed to design and develop a drug-eluting polymeric contact lens for the effective delivery of moxifloxacin (MF) and dexamethasone (DM). The polymeric contact lens was prepared using chitosan, glycerol, and polyethylene glycol. MF and DM were loaded into the contact lens, both separately and in combination. The MF and DM loaded contact lenses were characterized for thickness, swelling index, surface topography, and mucoadhesion strength. Furthermore, studies were performed to understand the in vitro drug release behavior, ex vivo corneal permeation, and in vitro and in vivo antimicrobial activity. The drug-loaded contact lens was compared with the standard drug solutions. The physical characteristics of the polymeric contact lens were similar to the commercially available contact lens. Compared to the topically applied standard drug solutions, the drug-loaded contact lens showed significantly (p < 0.05) greater corneal drug distribution after 24 h incubation. In vitro and in vivo antimicrobial activity of the MF loaded contact lens was superior to the standard drug solution. In vivo drug distribution studies showed greater tissue concentration of MF in cornea, sclera, and aqueous humor with contact lens application compared with drug solutions. Overall, the polymeric contact lens was efficient in delivering MF and DM at required therapeutic concentrations. The findings from the present study show that drug-eluting contact lenses could be used in post-operative conditions to prevent ocular infections.

Corneal Infection Models: Tools to Investigate the Role of Biofilms in Bacterial Keratitis

Bacterial keratitis is a corneal infection which may cause visual impairment or even loss of the infected eye. It remains a major cause of blindness in the developing world. Staphylococcus aureus and Pseudomonas aeruginosa are common causative agents and these bacterial species are known to colonise the corneal surface as biofilm populations. Biofilms are complex bacterial communities encased in an extracellular polymeric matrix and are notoriously difficult to eradicate once established. Biofilm bacteria exhibit different phenotypic characteristics from their planktonic counterparts, including an increased resistance to antibiotics and the host immune response. Therefore, understanding the role of biofilms will be essential in the development of new ophthalmic antimicrobials. A brief overview of biofilm-specific resistance mechanisms is provided, but this is a highly multifactorial and rapidly expanding field that warrants further research. Progression in this field is dependent on the development of suitable biofilm models that acknowledge the complexity of the ocular environment. Abiotic models of biofilm formation (where biofilms are studied on non-living surfaces) currently dominate the literature, but co-culture infection models are beginning to emerge. In vitro, ex vivo and in vivo corneal infection models have now been reported which use a variety of different experimental techniques and animal models. In this review, we will discuss existing corneal infection models and their application in the study of biofilms and host-pathogen interactions at the corneal surface.

Toll-like receptor gene polymorphisms in patients with keratitis

OBJECTIVE

To investigate differences in SNPs in TLR genes between people who had keratitis and controls in an Indian population.

METHODS

145 cases of keratitis and 189 matched controls were recruited. DNA was extracted from peripheral blood. Single nucleotide polymorphisms (SNP) in TLR2 (n = 6), TLR4 (n = 15), TLR5 (n = 13) and TLR9 (n = 10) were analysed. The risk of developing keratitis was assessed based on allele, genotype and haplotype associations.

RESULTS

For all cases of keratitis, the TLR4 SNP rs4986791 TC genotype frequency was significantly higher in cases (p = 0.006, OR = 1.96, 95 % CI 1.19-3.2). Including cases of only microbial keratitis (MK) revealed that genotypes in TLR2 SNP rs5743706 TA (p = 0.0001; OR = 8.61; 95 % CI 2.59-28.56)), TLR4 SNP s4986791 TC (p = 0.002; OR = 2.65; 95 % CI 1.39-5.07) were significantly more common for MK, whereas the TLR5 SNP rs2241096 A allele (p = 0.00316, OR = 0.42, 95 % CI 0.2-0.9286) and GA genotype (p = 0.016; OR = 0.45; 95 % CI 0.23-0.86) was significantly less common in MK cases. The TLR2 SNP rs5743706 genotype TA was significantly less common in the sterile keratitis (SK) group (p = 0.004, OR = 0.43, 95 %CI 0.24-0.77). Haplotype analysis of MK compared to controls showed that TLR2 AT was more common in controls (p = 0.003); TLR4 ACAC was more common in cases (p = 0.004); TLR5 TGGCA was more common in controls (p = 0.001).

CONCLUSION

The present study revealed multiple associations between variants across TLR genes, which may have implications for understanding the underlying host factors, risk of developing keratitis and molecular pathogenesis in keratitis.

A randomized masked pilot clinical trial to compare the efficacy of topical 1% voriconazole ophthalmic solution as monotherapy with combination therapy of topical 0.02% polyhexamethylene biguanide and 0.02% chlorhexidine in the treatment of Acanthamoeba keratitis

PURPOSE

To compare the efficacy of topical voriconazole 1% and the combination therapy of 0.02% polyhexamethylene biguanide (PHMB) and 0.02% chlorhexidine for the treatment of Acanthamoeba keratitis (AK).

METHODS

This is a prospective, pilot, double-masked randomized comparative study. Twenty-three eyes of 23 patients with microbiologically (smear and/or growth on culture) confirmed AK were randomized to group BG (PHMB 0.02% and chlorhexidine 0.02%) or group VZ (voriconazole 1%). Primary outcome measure was change in geometric mean (GM) of the corneal ulcer size at final visit. Secondary outcome measures were change in visual acuity.

RESULTS

Out of 71 patients with confirmed AK seen during study period, 23 patients were recruited and 18 patients completed minimum 2 weeks of treatment and further analyzed. Ten patients received BG, whereas eight received VZ. Median ulcer size measured as GM of infiltrate decreased from 5.7 mm (IQR, 5.3-6.5 mm) (p = 0.02) to 1 mm (IQR, 0-4.3 mm) in group BG and from 4.5 mm (IQR, 1.8-5.1 mm) (p < 0.05) to 0.7 mm (IQR, 0-1.6 mm) in VZ group. Median visual acuity improved from 1.79 (IQR, 1.48-2.78) to 1.10 (IQR, 0.48-1.79) in BG group (p = 0.02) and from 1.60 (IQR, 1.00-2.78) to 0.80 (IQR, 0.48-1.30) in VZ group (p = 0.18).

CONCLUSION

These outcomes suggest that topical VZ as a monotherapy in AK treatment is effective and comparable to BG combination therapy but needs trials with larger sample size and longer follow-up to provide conclusive evidence.

Delays and barriers to early treatment initiation for childhood tuberculosis in India

BACKGROUND: India accounts for 27% of global childhood tuberculosis (TB) burden. Understanding barriers to early diagnosis and treatment in children may improve care and outcomes.METHODS: A cross-sectional study was performed among 89 children initiated on anti-TB treatment from a public hospital in Pune during 2016, using a structured questionnaire and hospital records. Health care providers (HCPs) were defined as medical personnel consulted about the child's TB symptoms. Time-to-treatment initiation (TTI) was defined as the number of days between onset of TB symptoms and anti-TB treatment initiation. Based on Revised National TB Control Programme recommendations, delayed TTI was defined as >28 days.RESULTS: Sixty-seven (75%) of 89 enrolled children had significant TTI delays (median 51 days, interquartile range [IQR] 27-86). Sixty-six (74%) children visited 1-8 HCPs in the private sector before approaching the public sector. The median HCP delay was 28 days (IQR 10-75). Bacille Calmette-Guérin vaccination (aOR 10.96, P = 0.04) and loss of appetite (aOR 4.44, P = 0.04) were associated with delayed TTI.CONCLUSION: The majority of the children had TTI delays due to delays by HCPs in the private sector. Strengthening HCP competency in TB symptom screening and encouraging early referrals are crucial for rapid scaling up of early treatment initiation in childhood TB.

Establishing a Porcine Ex Vivo Cornea Model for Studying Drug Treatments against Bacterial Keratitis

When developing novel antimicrobials, the success of animal trials is dependent on accurate extrapolation of antimicrobial efficacy from in vitro tests to animal infections in vivo. The existing in vitro tests typically overestimate antimicrobial efficacy as the presence of host tissue as a diffusion barrier is not accounted for. To overcome this bottleneck, we have developed an ex vivo porcine corneal model of bacterial keratitis using Pseudomonas aeruginosa as a prototypic organism. This article describes the preparation of the porcine cornea and protocol for establishment of the infection. Bespoke glass molds enable straightforward setup of the cornea for infection studies. The model mimics in vivo infection as bacterial proliferation is dependent on the ability of the bacterium to damage corneal tissue. Establishment of infection is verified as an increase in the number of colony forming units assessed via viable plate counts. The results demonstrate that infection can be established in a highly reproducible fashion in the ex vivo corneas using the method described here. The model can be extended in the future to mimic keratitis caused by microorganisms other than P. aeruginosa. The ultimate aim of the model is to investigate the effect of antimicrobial chemotherapy on the progress of bacterial infection in a scenario more representative of in vivo infections. In so doing, the model described here will reduce the use of animals for testing, improve success rates in clinical trials and ultimately enable rapid translation of novel antimicrobials to the clinic.

Outcome of therapeutic deep anterior lamellar keratoplasty in advanced Acanthamoeba keratitis

Purpose

To report and analyze the outcomes of therapeutic deep anterior lamellar keratoplasty (DALK) in patients with advanced Acanthamoeba keratitis (AK).

Methods

Medical records of microbiologically confirmed AK, underwent DALK from 2004 to 2017, were reviewed and the data related to early and late outcome including complications were retrieved. Outcome of cases with largest diameter of infiltrate ≥8 mm at the time of surgery (advanced keratitis) were analyzed and compared with those with less severe keratitis (infiltrate size less than 8 mm).

Results

Out of 23 patients of AK in whom DALK was performed, ten (43.4%) patients had advanced keratitis. Mean age of these patients was 38.7 ± 8.6 years (range, 25 to 56). Median visual acuity at presentation was 2.78 (IQR, 1.79-3.0) that improved to 1.79 (IQR, 0.70-2.78) postoperatively. Early complications included recurrence of AK in 2 (20%), Descemet's membrane detachment in 5 (50%), and persistent epithelial defect in 3 (30%) cases. Overall, 6 (60%) grafts failed, whereas 4 (40%) patients had clear graft at their last follow-up. Median follow-up of these cases was 5 months (IQR, 1.4-11.4). One graft developed stromal rejection, which resolved with increased dose of corticosteroids. In comparison, DALK performed for less severe keratitis (N = 13) had 1 (7.6%) recurrence and 2 (15.8%) grafts failure (OR, 8.25). The probability of one-year graft survival and eradication of infection was 32% and 74.1%, respectively, in advanced cases compared to 91.6% and 83.9% in less severe cases.

Conclusion

Outcome of DALK in advanced Acanthamoeba keratitis is less favorable compared to those carried out for less severe keratitis cases.

Characterization of Ocular Clinical Isolates of Pseudomonas aeruginosa from Non-Contact Lens Related Keratitis Patients from South India

P. aeruginosa is the most common Gram-negative organism causing bacterial keratitis. Pseudomonas utilizes various virulence mechanisms to adhere and colonize in the host tissue. In the present study, we examined virulence factors associated with thirty-four clinical P. aeruginosa isolates collected from keratitis patients seeking care at L V Prasad Eye Institute, Hyderabad. The virulence-associated genes in all the isolates were genotyped and characteristics such as antibiotic susceptibility, biofilm formation, swarming motility, pyoverdine production and cell cytotoxicity were analyzed. All the isolates showed the presence of genes related to biofilm formation, alkaline proteases and elastases; however, there was a difference in the presence of genes related to the type III secretion system (T3SS). A higher prevalence of exoU+ genotype was noted in the drug-resistant isolates. All the isolates were capable of forming biofilms and more than 70% of the isolates showed good swarming motility. Pyoverdine production was not associated with the T3SS genotype. In the cytotoxicity assay, the presence of exoS,exoU or both resulted in higher cytotoxicity compared to the absence of both the genes. Overall, our results suggest that the T3SS profile is a good indicator of P. aeruginosa virulence characteristics and the isolates lacking the effector genes may have evolved alternate mechanisms of colonization in the host.

Cyclam-based antibacterial molecules eradicate Gram-negative superbugs with potent efficacy against human corneal infection

Cyclam-based antibacterial molecules (CAMs) that display potent activity against both the planktonic and stationary phase of multidrug-resistant Gram-negative bacteria were rationally designed.

Novel drug delivery methods for the treatment of keratitis: moving away from surgical intervention

Introduction: Corneal ulceration is one of the leading causes of blindness especially in low- and mid-income countries (LMICs). Surgical treatment of microbial keratitis is associated with multiple challenges that include non-availability of donor corneal tissues, lack of trained corneal surgeons, and poor compliance to follow up care. As a result, the surgery fails in 70-90% cases. Therefore, improving outcome of medical treatment and thereby avoiding the need for the surgery is an unmet need in the care of corneal ulcer cases.Areas covered: In this review article, the authors have tried to compile information on the novel drug-delivery systems that have potential to enhance success of medical management. We have discussed the following systems: cyclodextrins, gel formulations, colloidal system, nanoformulations, drug-eluting contact lens, microneedle patch, and ocular inserts.Expert opinion: The goals of corneal ulcer treatment are as follows: rapid eradication of causative microorganisms, control of damage from induced inflammation and microbial toxins, and facilitation of repair. The ocular surface anatomy poses several challenges for drug delivery using standard topical therapy. The novel drug-delivery systems mentioned above aim to enhanced tear solubility; superior stability; improved bio-availability; reduced toxicity; besides facilitating targeted drug delivery and convenience of administration.