Multi-Scale Convolutional Neural Network for Accurate Corneal Segmentation in Early Detection of Fungal Keratitis.

Microbial keratitis is an infection of the cornea of the eye that is commonly caused by prolonged contact lens wear, corneal trauma, pre-existing systemic disorders and other ocular surface disorders. It can result in severe visual impairment if improperly managed. According to the latest World Vision Report, at least 4.2 million people worldwide suffer from corneal opacities caused by infectious agents such as fungi, bacteria, protozoa and viruses. In patients with fungal keratitis (FK), often overt symptoms are not evident, until an advanced stage. Furthermore, it has been reported that clear discrimination between bacterial keratitis and FK is a challenging process even for trained corneal experts and is often misdiagnosed in more than 30% of the cases. However, if diagnosed early, vision impairment can be prevented through early cost-effective interventions. In this work, we propose a multi-scale convolutional neural network (MS-CNN) for accurate segmentation of the corneal region to enable early FK diagnosis. The proposed approach consists of a deep neural pipeline for corneal region segmentation followed by a ResNeXt model to differentiate between FK and non-FK classes. The model trained on the segmented images in the region of interest, achieved a diagnostic accuracy of 88.96%. The features learnt by the model emphasize that it can correctly identify dominant corneal lesions for detecting FK

Cryopreservation in Ophthalmology

Amniotic membranes (AMs) and corneas are critical materials in ocular surface reconstruction. AM has specific structures (e.g., basement and two types of cells with stemness characteristics: amniotic epithelial cells and amniotic mesenchymal cells), which contribute to its attractive physical and biological properties that make it fundamental to clinical application. The corneal endothelial cell is a vital part of the cornea, which can influence postoperative vision directly. However, widespread use of fresh AM and cornea has been limited due to their short use span and safety concerns. To overcome these concerns, different preservation methods have been introduced. Cryopreservation is distinguished from many preservation methods for its attractive advantages of prolonged use span, optimally retained tissue structure, and minimized infection risk. This review will focus on recent advances of cryopreserved AM and cornea, including different cryopreservation methods and their indications in ophthalmology

Accuracy of artificial intelligence model for infectious keratitis classification: a systematic review and meta-analysis

BackgroundInfectious keratitis (IK) is a sight-threatening condition requiring immediate definite treatment. The need for prompt treatment heavily depends on timely diagnosis. The diagnosis of IK, however, is challenged by the drawbacks of the current “gold standard.” The poorly differentiated clinical features, the possibility of low microbial culture yield, and the duration for culture are the culprits of delayed IK treatment. Deep learning (DL) is a recent artificial intelligence (AI) advancement that has been demonstrated to be highly promising in making automated diagnosis in IK with high accuracy. However, its exact accuracy is not yet elucidated. This article is the first systematic review and meta-analysis that aims to assess the accuracy of available DL models to correctly classify IK based on etiology compared to the current gold standards.MethodsA systematic search was carried out in PubMed, Google Scholars, Proquest, ScienceDirect, Cochrane and Scopus. The used keywords are: “Keratitis,” “Corneal ulcer,” “Corneal diseases,” “Corneal lesions,” “Artificial intelligence,” “Deep learning,” and “Machine learning.” Studies including slit lamp photography of the cornea and validity study on DL performance were considered. The primary outcomes reviewed were the accuracy and classification capability of the AI machine learning/DL algorithm. We analyzed the extracted data with the MetaXL 5.2 Software.ResultsA total of eleven articles from 2002 to 2022 were included with a total dataset of 34,070 images. All studies used convolutional neural networks (CNNs), with ResNet and DenseNet models being the most used models across studies. Most AI models outperform the human counterparts with a pooled area under the curve (AUC) of 0.851 and accuracy of 96.6% in differentiating IK vs. non-IK and pooled AUC 0.895 and accuracy of 64.38% for classifying bacterial keratitis (BK) vs. fungal keratitis (FK).ConclusionThis study demonstrated that DL algorithms have high potential in diagnosing and classifying IK with accuracy that, if not better, is comparable to trained corneal experts. However, various factors, such as the unique architecture of DL model, the problem with overfitting, image quality of the datasets, and the complex nature of IK itself, still hamper the universal applicability of DL in daily clinical practice

Topical chlorhexidine 0.2% versus topical natamycin 5% for fungal keratitis in Nepal: rationale and design of a randomised controlled non-inferiority trial.

INTRODUCTION: Fungal infections of the cornea, fungal keratitis (FK), are challenging to treat. Current topical antifungals are not always effective and are often unavailable, particularly in low-income and middle-income countries where most cases occur. Topical natamycin 5% is usually first-line treatment, however, even when treated intensively, infections may progress to perforation of the eye in around a quarter of cases. Alternative antifungal medications are needed to treat this blinding disease.Chlorhexidine is an antiseptic agent with antibacterial and antifungal properties. Previous pilot studies suggest that topical chlorhexidine 0.2% compares favourably with topical natamycin. Full-scale randomised controlled trials (RCTs) of topical chlorhexidine 0.2% are warranted to answer this question definitively. METHODS AND ANALYSIS: We will test the hypothesis that topical chlorhexidine 0.2% is non-inferior to topical natamycin 5% in a two-arm, single-masked RCT. Participants are adults with FK presenting to a tertiary ophthalmic hospital in Nepal. Baseline assessment includes history, examination, photography, in vivo confocal microscopy and cornea scrapes for microbiology. Participants will be randomised to alternative topical antifungal treatments (topical chlorhexidine 0.2% and topical natamycin 5%; 1:1 ratio, 2-6 random block size). Patients are reviewed at day 2, day 7 (with reculture), day 14, day 21, month 2 and month 3. The primary outcome is the best spectacle corrected visual acuity (BSCVA) at 3 months. Primary analysis (intention to treat) will be by linear regression, with treatment arm and baseline BSCVA prespecified covariates. Secondary outcomes include epithelial healing time, scar/infiltrate size, ulcer depth, hypopyon size, perforation and/or therapeutic penetrating keratoplasty (corneal transplant), positive reculture rate (day 7) and quality of life (EuroQol-5 dimensions, WHO/PBD-VF20, WHOQOL-BREF). ETHICS AND DISSEMINATION: The Nepal Health Research Council, the Nepal Department of Drug Administration and the London School of Hygiene and Tropical Medicine ethics committee have approved the trial. The results will be presented at local and international meetings and submitted to peer-reviewed journals for publication. TRIAL REGISTRATION NUMBER: ISRCTN14332621; pre-results

The Epidemiology of Microbial Keratitis in South Western Uganda

Background: Microbial Keratitis (MK) is the leading cause of unilateral blindness after cataract in Tropical regions and is responsible for 2 million cases of blindness per year. In Sub-Saharan Africa, MK is a neglected problem, most ophthalmic centres do not have diagnostic services, patients present late, appropriate drugs are often not available, corneal transplant services are rarely available. Subsequently, outcomes are poor in this area. Currently there are very limited data to guide policy and practice. Methods: In a main cohort design, individuals with MK presenting to the two referral eye hospitals in South Western Uganda were enrolled over a one-year period. Clinical history and presentation journey were recorded. Their eyes were carefully examined, and samples were collected for microbiology. Patients were tested for HIV and Diabetes. At three months, patients were followed up in their homes and at this point healthy community controls were enrolled to compare risk factors in a nested case-control study and assess the impact of the disease on the Quality of Life (QoL). A separate situation analysis survey of lower health centres was additionally conducted to understand the role of the health system in management of MK. Results: Three hundred and thirteen individuals were enrolled. Median age was 47 years (ra nge 18-96) and 174 (56%) were male. Median presentation time to the eye hospital was 17 days from onset (IQR 8-32). Trauma was reported by 29%. Majority presented with severe in fections (median infiltrate size 5.2 mm); 47% were blind in the affected eye (vision <3/60), fu ngal cases were 62%. At 3-months, 30% of participants were blind in the affected eye, while 9% had lost their eye from the infection. Predictors of poor vision at 3-months were: baseline vision (aOR 2.98 [95%CI 2.12-4.19], p<0.0001), infiltrate size (aOR 1.19 [95%CI 1.03-1.3 6], p<0.020) and perforation at presentation (aOR 9.93 [95% CI 3.70-26.6], p<0.0001). Traditional Eye Medicine (TEM) use was reported in 188/313. TEM users had a delayed presentation; median presenting time 18 days versus 14 days, p= 0.005; had larger ulcers 5.6 mm versus 4.3 mm p=0.0005; a worse presenting visual acuity median logarithm of the minimum angle of resolution (Log MAR) 1.5 versus 0.6, p=0.005; and, a worse visual acuity at 3 months median Log MAR 0.6 versus 0.2, p=0.010. In the qualitative analysis, reasons for TEM use included lack of confidence in conventional medicine, health system breakdown, poverty, fear of the eye hospital, cultural belief in TEM, influence from traditional healers, personal circumstances and ignorance. In the case-control analysis, HIV OR 83.5 (95%CI 2.01-3456), p=0.020, Diabetes OR 9.38 (95% CI 1.48-59.3), p=0.017 and a farming occupation OR 2.60 (95%CI 1.21-5.57), p=0.014 were main risk factors of MK. In the Quality of Life (QoL) analysis, mean QoL scores of the cases were lower than controls across all domains. Determinants of QoL among the cases at 3-months included visual acuity at 3-months and history of eye loss. Although most patients presented early to the primary health centres (median 2days IQR 0-5 days), there were severe weaknesses along the health system in identification and early referral of MK. Only 12% of the health workers could make a diagnosis of MK. None of the health facilities had a stock of the recommended first line treatment options for MK (ciprofloxacin and Natamycin eye drops). Conclusion: This is the first large epidemiological cohort in SSA studying MK and provides a baseline understanding of the epidemiology, aetiology and outcomes, and what needs to be done to improve the situation and reduce the devastating visual outcomes currently experienced by many peopl

Plasma Rich in Growth Factors Membrane as Coadjuvant Treatment in the Surgery of Ocular Surface Disorders

To evaluate the safety and efficacy of the surgical use of plasma rich in growth factors fibrin membrane (mPRGF) in different ocular surface pathologies.Fifteen patients with different corneal and conjunctival diseases were included in the study. Patients were grouped according to the use of mPRGF as graft (corneal and/or conjunctival) or dressing; they were also grouped according to the surgical subgroup of intervention (persistent corneal ulcer [PCU], keratoplasty, superficial keratectomy, corneal perforation, and pterygium). Best corrected visual acuity, intraocular pressure (IOP), inflammation control time (ICT), mPRGF AT (PRGF membrane absorption time), and the healing time of the epithelial defect (HTED) were evaluated throughout the clinical follow-up time. Safety assessment was also performed reporting all adverse events.mPRGF showed a total closure of the defect in 13 of 15 patients (86.7%) and a partial closure in 2 patients (13.3%). The mean follow-up time was 11.14.2 (4.8-22.8) months, the mean ICT was 2.5 +/- 1.1 (1.0-4.0) months, the mean mPRGF AT was 12.4 +/- 2.0 (10.0-16.0) days, and for the global HTED the mean was 2.9 +/- 1.2 (1-4.8) months. Results showed an improvement in BCVA in all patients, with an overall improvement of 2.9 in Vision Lines. The BCVA significantly improved (P.05) throughout the clinical follow-up time. No adverse events were reported after mPRGF use.The mPRGF is effective and safe as coadjuvant treatment in surgeries related with ocular surface disorders, being an alternative to the use of amniotic membrane. The mPRGF accelerates tissue regeneration after ocular surface surgery thus minimizing inflammation and fibrosis.This study received funding from the Ministry of Economy and Competitiveness of the Spanish Government, within the project denominated SURFEYE (reference RTC-2014-2375-1)

Current and emerging therapies for corneal infection: a clinical and laboratory study

Corneal infection or infectious keratitis (IK) is a major cause for corneal blindness worldwide. Broad-spectrum antimicrobial therapy is currently the mainstay of treatment for IK, but the efficacy is being challenged by the emergence of antimicrobial resistance. Host defense peptides (HDPs), also known as antimicrobial peptides (AMPs), are evolutionarily conserved molecules of innate immune system that are found in all kingdoms of life. HDPs have shown promise as a novel class of antimicrobial therapeutics due to their broad-spectrum and rapid antimicrobial activity against a wide array of infection with minimal risk of developing resistance. At the ocular surface, HDPs, particularly human cathelicidin (LL-37) and human beta-defensins (HBDs), have been shown to play a vital role during IK. The first part of this work (Chapter 2 to Chapter 4) consisted of a body of work examining the epidemiology, causes, clinical characteristics, outcomes, and prognostic factors of IK in Nottingham, UK. IK was shown to be a persistent burden in Nottingham over the past decade, with ocular surface diseases, contact lens wear and systemic immunosuppression being the most common risk factors. More than 50% of the patients with IK required hospitalisation for intensive treatment, highlighting the burden of the disease on the patients and the healthcare system. Poor clinical outcome was significantly affected by older age, large infiltrate size and poor presenting vision. The second part (Chapter 5 and Chapter 6) systematically examined the effectiveness and safety of adjuvant therapeutic corneal collagen cross-linking (PACK-CXL) and amniotic membrane transplant for treating IK, in addition to standard antimicrobial therapy. The meta-analyses demonstrated that both interventions significantly expedited the healing of IK, though the overall quality of evidence was low, highlighting the need for further high-quality randomised controlled trials. The third part (Chapter 7 and Chapter 8) highlighted a body of work in developing a new class of HDP-based antimicrobial therapy for IK based on hybrid derivatives of human cathelicidin (LL-37) and human beta-defensins-1 to -3. CaD23, derived from LL-37 and HBD-2, exhibited good in vitro efficacy against Gram-positive bacteria and moderate efficacy against Gram-negative bacteria. It demonstrated a rapid antimicrobial activity, which was likely attributed to its membrane-permeabilising activity, supported by SYTOX green dye uptake assay and molecular dynamics simulation study. CaD23 was also shown to exhibit a strong additive effect when used in combination with conventional antibiotics against Gram-positive bacteria. Finally, CaD23 exhibited good antimicrobial efficacy against Gram-positive bacteria (1.2 logCFU or 94% reduction in the bioburden) in a murine bacterial keratitis model. The discovery of CaD23 has provided a new scaffold for future development of newer generations of hybrid peptides

Corticosteroid-Antibiotic Interactions in Bacteria that Cause Corneal Infection

Purpose: Although a comprehensive knowledge of antibiotic/corticosteroid combinations is essential for the appropriate treatment of eye infections, the impact of their co-administration has not been well studied to date. A systematic pharmacodynamic/pharmacokinetic study to determine the effects of cotreatment with various antibiotics and corticosteroids was conducted. Methods: Four bacterial strains, seven antibiotics, and four corticosteroids were used in the analyses. Drug interactions were evaluated by considering antibacterial effects with a checkerboard assay and intracellular concentrations in human corneal epithelial cells. Results: The drug combinations that showed the most stable effects against Pseudomonas aeruginosa was levofloxacin-prednisolone. Stable combinations against the three types of Gram-positive bacteria were neomycin-prednisolone, ofloxacin-dexamethasone, ofloxacin-prednisolone, and polymyxin-dexamethasone. The cellular concentrations were changed for the gatifloxacin-fluorometholone, moxifloxacin-fluorometholone, tobramycin-dexamethasone, and tobramycin-prednisolone combinations. Conclusions: Loteprednol and fluorometholone reduced the antibacterial effects of all of the tested antibiotics in this study. Dexamethasone and prednisolone showed various effects in this regard, depending on the co-administered antibiotic. Prior knowledge of specific antibiotic/corticosteroid interactions provides valuable information to clinical practitioners by combining data on the antibacterial and intracellular uptake effects of their co-administration. Translational relevance: When using antibiotics and corticosteroids, drug combinations can be selected by referring to the results of this study.ope