Intrastromal Corneal Ring Implants Associated Bacterial Infections

PURPOSE

This study examines the incidence of infection and resistance associated with Intracorneal Ring Segment (ICRS) implantation, a common outpatient surgical treatment for correcting refractive errors and corneal ectatic diseases. Although ICRS procedures are typically safe and reversible, there is a low but notable risk of microbial infections, which require prompt and sometimes invasive treatment.

METHODS

Three electronic databases, PubMed, Web of Science (WoS), and Scopus, were utilised to search for literature according to PRISMA guidelines to identify infections related to the implantation of ICRS in the cornea between January 2000 and December 2022.

RESULTS

Gram-positive organisms were involved in 86% of cases: 35.7% S. aureus, 25% coagulase-negative staphylococci species, 17.8% streptococci and 7.1% Nocardia species. Less commonly recorded were Gram-negative bacteria (14%), with Pseudomonas aeruginosa (circa 10%) and Klebsiella pneumonia (4%) being the most common Gram-negative bacteria. In rare cases, fungi have also been reported. ICRS-related bacterial infections can be categorised into early or late onset. Early onset infection typically manifests within the first few weeks after implantation and is often associated with contamination during surgery, unhygienic practices, or inadequate sterilisation techniques. On the other hand, late-onset infection may develop months or even years after the initial procedures and may be associated with persistent bacterial colonisation, secondary infections, or prolonged use of prophylactic antibiotics. S aureus is encountered in both early and late-onset infections, while Nocardia species and K. pneumoniae have generally been reported to occur in late-onset infections. In addition, vision recovery from S. aureus infections tends to be poor compared to other bacterial infections.

CONCLUSION

S. aureus is a predominant pathogen that often requires surgical intervention with poor outcomes. Early infections result from incision gaps and ring segment rubbing, while late infections are linked to prolonged antibiotic use. Further research is needed on novel antimicrobial ICRS to procure the vision.

Epidemiology of Microbial Keratitis at a Tertiary Care Hospital in Southern Thailand

Purpose

This study aimed to ascertain the microbial profiles and predisposing risk factors for microbial keratitis and to analyze the trend of mixed microbial infection cases over 8 years.

Patients and Methods

In this retrospective analysis, we reviewed the electronic medical records of inpatients diagnosed with microbial keratitis between January 2012 and December 2019. Data on demographics, risk factors, and causative pathogens were analyzed. Multivariate logistic regression models were utilized to identify risk factors associated with pathogens.

Results

This study included 640 eyes of 638 patients. Trauma was the most common predisposing risk factor (57.2%), followed by a combination of factors (14.4%). Among diagnostic test results, bacteria, fungi, and mixed pathogens were identified in 46.72%, 46.56%, and 21.41% of cases, respectively. Positive culture results were obtained in 324 eyes (53.6%), with Pseudomonas aeruginosa (25.1%) and Fusarium spp. (17.4%) being the most prevalent pathogens. In the multivariate logistic regression model, contact lens use, presence of diabetes mellitus, and HIV infection were statistically significant risk factors for Pseudomonas aeruginosa infection (p = 0.001, p = 0.046, and p = 0.04, respectively). Trauma was associated with Fusarium spp. infection (p = 0.001). An increase in the percentage of mixed microbial infection cases was observed when comparing the periods of 2016-2019 with 2012-2015 (p = 0.023).

Conclusion

Bacteria and fungi are equally common causes of microbial keratitis, with Pseudomonas aeruginosa and Fusarium spp. being the predominant pathogens causing bacterial and fungal infections. Trauma is the primary predisposing risk factor for microbial keratitis. There was a notable increase in mixed infection cases over the study period.

Trends and Clinical Outcomes of Fungal Keratitis in Canada: a 20-year Retrospective Multicentre Study

PURPOSE

An increase in fungal and particularly filamentous keratitis has been observed in many geographic areas, mostly in contact lens wearers. This study seeks to characterize long-term trends in fungal keratitis in a continental climate area to provide guidance for diagnosis and treatment.

DESIGN

Retrospective multicentric case series.

METHODS

Cases of microbiology-confirmed fungal keratitis from 2003 to 2022 presenting to tertiary care centers across Canada were included. Charts were reviewed for patient demographics, risk factors, visual acuity, and treatments undertaken.

RESULTS

A total of 138 patients were identified: 75 had yeast keratitis while 63 had filamentous keratitis. Patients with yeast keratitis had more ocular surface disease (79% vs 28%) while patients with filamentous keratitis wore more refractive contact lenses (78% vs 19%). Candida species accounted for 96% of all yeast identified, while Aspergillus (32%) and Fusarium (26%) were the most common filamentous fungi species. The mean duration of treatment was 81 ± 96 days. Patients with yeast keratitis did not have significantly improved visual acuity with medical treatment (1.8 ± 1 LogMAR to 1.9 ± 1.5 LogMAR, p = 0.9980), in contrast to patients with filamentous keratitis (1.4 ± 1.2 LogMAR to 1.1 ± 1.3 LogMAR, p = 0.0093).

CONCLUSIONS

Fungal keratitis is increasing in incidence, with contact lenses emerging as one of the leading risk factors. Significant differences in the risk factors and visual outcomes exist between yeast keratitis and filamentous keratitis which may guide diagnosis and treatment.

Post-Keratoplasty Microbial Keratitis in the Era of Lamellar Transplants-A Comprehensive Review

Microbial keratitis in a post-transplant cornea should be considered a distinct entity from microbial keratitis in a non-transplant cornea. Firstly, the use of immunosuppressive treatments and sutures in corneal transplants changes the etiology of keratitis. Secondly, corneal transplant has an impact on corneal biomechanics and structure, which facilitates the spread of infection. Finally, the emergence of lamellar transplants has introduced a new form of keratitis known as interface keratitis. Given these factors, there is a clear need to update our understanding of and management strategies for microbial keratitis following corneal transplantation, especially in the era of lamellar transplants. To address this, a comprehensive review is provided, covering the incidence, risk factors, causes, and timing of microbial keratitis, as well as both clinical and surgical management approaches for its treatment in cases of penetrating and lamellar corneal transplants.

Automatic Classification of Slit-Lamp Photographs by Imaging Illumination

PURPOSE

The aim of this study was to facilitate deep learning systems in image annotations for diagnosing keratitis type by developing an automated algorithm to classify slit-lamp photographs (SLPs) based on illumination technique.

METHODS

SLPs were collected from patients with corneal ulcer at Kellogg Eye Center, Bascom Palmer Eye Institute, and Aravind Eye Care Systems. Illumination techniques were slit beam, diffuse white light, diffuse blue light with fluorescein, and sclerotic scatter (ScS). Images were manually labeled for illumination and randomly split into training, validation, and testing data sets (70%:15%:15%). Classification algorithms including MobileNetV2, ResNet50, LeNet, AlexNet, multilayer perceptron, and k-nearest neighborhood were trained to distinguish 4 type of illumination techniques. The algorithm performances on the test data set were evaluated with 95% confidence intervals (CIs) for accuracy, F1 score, and area under the receiver operator characteristics curve (AUC-ROC), overall and by class (one-vs-rest).

RESULTS

A total of 12,132 images from 409 patients were analyzed, including 41.8% (n = 5069) slit-beam photographs, 21.2% (2571) diffuse white light, 19.5% (2364) diffuse blue light, and 17.5% (2128) ScS. MobileNetV2 achieved the highest overall F1 score of 97.95% (CI, 97.94%-97.97%), AUC-ROC of 99.83% (99.72%-99.9%), and accuracy of 98.98% (98.97%-98.98%). The F1 scores for slit beam, diffuse white light, diffuse blue light, and ScS were 97.82% (97.80%-97.84%), 96.62% (96.58%-96.66%), 99.88% (99.87%-99.89%), and 97.59% (97.55%-97.62%), respectively. Slit beam and ScS were the 2 most frequently misclassified illumination.

CONCLUSIONS

MobileNetV2 accurately labeled illumination of SLPs using a large data set of corneal images. Effective, automatic classification of SLPs is key to integrating deep learning systems for clinical decision support into practice workflows.

Factors Associated With Laboratory Test Negativity Following a Transition in Specimen Collection in Microbial Keratitis Cases

PURPOSE

Negative laboratory results make targeting microbial keratitis treatment difficult. We investigated factors associated with laboratory negativity in patients with microbial keratitis in the context of a transition to a new specimen collection method.

METHODS

Microbial keratitis patients with associated laboratory tests were identified in the electronic health record of a tertiary care facility from August 2012 to April 2022. Patient demographics and laboratory results were obtained. Random sampling of 50% of charts was performed to assess the impact of the ocular history and pretreatment measures. The relationship between probability of negative laboratory results with demographics, ocular history, pretreatment measures, and utilization of a new specimen collection method (i.e. ESwab) was evaluated by multivariable logistic regression.

RESULTS

Of 3395 microbial keratitis patients identified, 31% (n = 1051) had laboratory tests. Laboratory testing increased over time (slope = 2.5% per year, p < 0.001; 19.6% in 2013 to 42.2% in 2021). Laboratory negative rate increased over time (slope = 2.2% per year, p = 0.022; 48.5% in 2013 to 62.3% in 2021). Almost one-third of patients (31.2%, n = 164) were pretreated with steroids. Over two-thirds of patients were pretreated with antibiotics (69.5%, n = 367). 56.5% (n = 297) of patients were outside referrals. In multivariable regression, patients with corticosteroid pretreatment had lower odds of negative laboratory results (odds ratio [OR] = 0.49, p = 0.001). There were higher odds of negative laboratory results for every additional antibiotic prescribed to a patient prior to presentation (OR = 1.30, p = 0.006) and for specimens collected using ESwabs (OR = 1.69, p = 0.005). Age, prior eye trauma, outside referrals, and contact lens wear were not significantly associated with negative laboratory results.

CONCLUSION

More microbial keratitis associated laboratory tests are being taken over time. Over 60% of tests were negative by 2022. Factors associated with negative laboratory test results included pretreatment with antibiotics and specimens collected with the new collection method.

Infectious Keratitis: Characterization of Microbial Diversity through Species Richness and Shannon Diversity Index

Purpose: To characterize microbial keratitis diversity utilizing species richness and Shannon Diversity Index. Methods: Corneal impression membrane was used to collect samples. All swabs were processed and analyzed by Biolab Laboratory (level V-SSN Excellence: ISO 9001:2015), Biolab Srl (Ascoli Piceno, Italy). DNA extraction, library preparation, and sequencing were performed in all samples. After sequencing, low-quality and polyclonal sequences were filtered out by the Ion software. At this point, we employed Kraken2 for microbial community analysis in keratitis samples. Nuclease-free water and all the reagents included in the experiment were used as a negative control. The primary outcome was the reduction in bacterial DNA (microbial load) at T1, expressed as a percentage of the baseline value (T0). Richness and Shannon alpha diversity metrics, along with Bray-Curtis beta diversity values, were calculated using the phyloseq package in R. Principal coordinate analysis was also conducted to interpret these metrics. Results: 19 samples were included in the study. The results exhibited a motley species richness, with the highest recorded value surpassing 800 species. Most of the samples displayed richness values ranging broadly from under 200 to around 600, indicating considerable variability in species count among the keratitis samples. Conclusions: A significant presence of both typical and atypical bacterial phyla in keratitis infections, underlining the complexity of the disease's microbial etiology.

Spontaneous expulsive choroidal hemorrhage in an elderly female with microbial keratitis

PURPOSE

To report spontaneous choroidal hemorrhage with the expulsion of intraocular contents in an elderly female as a complication of microbial keratitis.

METHODS

Retrospective case report along with imaging.

RESULTS

A 60-year-old female on treatment for microbial keratitis, presented with protrusion of intraocular contents and no perception of light in the right eye. Ophthalmic ultrasound demonstrated choroidal hemorrhage with coexistent retinal detachment and vitreous hemorrhage. She underwent uneventful evisceration for her condition.

CONCLUSION

Microbial keratitis needs aggressive medical treatment to prevent associated stromal infiltration and corneal weakening. In cases of microbial keratitis, if spontaneous choroidal hemorrhage occurs, due to thinning of the cornea and compromised integrity of the eyeball, it can lead to the complete expulsion of intraocular contents with unsalvageable loss of vision.

Synergistic Effect of Nilavembu Choornam-Gold Nanoparticles on Antibiotic-Resistant Bacterial Susceptibility and Contact Lens Contamination-Associated Infectious Pathogenicity

Antibiotic-resistant bacterial colonies mitigate rapid biofilm formation and have complex cell wall fabrications, making it challenging to penetrate drugs across their biofilm barriers. The objective of this study was to investigate the antibacterial susceptibility of antibiotic-resistant bacteria and contact lens barrenness. Nilavembu Choornam-Gold Nanoparticles (NC-GNPs) were synthesized using NC polyherbal extract and characterized by UV-visible spectrophotometer, SEM-EDX, XRD, Zeta sizer, FTIR, and TEM analysis. Contact lenses with overnight cultures of antibiotic-resistant bacteria K. pneumoniae and S. aureus showed significant differences in growth, biofilm formation, and infection pathogenicity. The NC-GNPs were observed in terms of size (average size is 57.6 nm) and surface chemistry. A zone of inhibition was calculated for K. pneumoniae 18.8 ± 1.06, S. aureus 23.6 ± 1.15, P. aeruginosa 24.16 ± 0.87, and E. faecalis 24.5 ± 1.54 mm at 24 h of NC-GNPs alone treatment. In electron microscopy studies, NC-GNP-treated groups showed nuclear shrinkage, nuclear disintegration, degeneration of cell walls, and inhibited chromosomal division. In contrast, normal bacterial colonies had a higher number of cell divisions and routinely migrated toward cell multiplications. NC-GNPs exhibited antibacterial efficacy against antibiotic-resistant bacteria when compared to NC extract alone. We suggest that NC-GNPs are highly valuable to the population of hospitalized patients and other people to reduce the primary complications of contact lens contamination-oriented microbial infection and the therapeutic efficiency of antibiotic-resistant bacterial pathogenicity.

Hydroquinine Enhances the Efficacy of Contact Lens Solutions for Inhibiting Pseudomonas aeruginosa Adhesion and Biofilm Formation

P. aeruginosa is one of the most common bacteria causing contact lens-related microbial keratitis (CLMK). Previous studies report that disinfecting solutions were ineffective in preventing biofilm formation. Solutions containing novel natural agents may be an excellent alternative for reducing the risk of CLMK. Here, we investigate the disinfecting properties of hydroquinine in combination with multipurpose solutions (MPSs) to prevent P. aeruginosa adhesion and biofilm formation. We examined the antibacterial, anti-adhesion, and anti-biofilm properties of hydroquinine-formulated MPSs compared to MPSs alone. Using RT-qPCR, hydroquinine directly affected the expression levels of adhesion-related genes, namely, cgrC, cheY, cheZ, fimU, and pilV, resulting in reduced adhesion and anti-biofilm formation. Using ISO 14729 stand-alone testing, hydroquinine met the criteria (>99.9% killing at disinfection time) against both P. aeruginosa reference and clinical strains. Using the crystal violet retention assay and FE-SEM, MPSs combined with hydroquinine were effective in inhibiting P. aeruginosa adhesion and destroying preexisting biofilms. This report is the first to highlight the potential utility of hydroquinine-containing formulations as a disinfecting solution for contact lenses, specifically for inhibiting adhesion and destroying biofilm. These findings may aid in the development of novel disinfectants aimed at combating P. aeruginosa, thereby potentially reducing the incidence of CLMK.

A Comparison of Culture Results and Visual Acuity in Contact Lens Related Microbial Keratitis

PURPOSE

Evaluate the effect of corneal and contact lens-related (CLR) culture results on visual acuity (VA) in patients with microbial keratitis (MK).

METHODS

MK patients with corneal and CLR cultures were identified in the University of Michigan electronic health record from August 2012 to April 2022. Test results were classified as laboratory-positive or laboratory-negative. Linear regression was used to examine trends of VA and associations between changes in VA (differences of VA at 90-day and baseline VA) and corneal and CLR culture results, after adjustment for baseline VA. One-sample t-tests were used to test if the slope estimates were different from zero.

RESULTS

MK patients (n = 50) were on average 49 years old (standard deviation = 20.9), 56% female, and 90% White. Positive corneal and CLR cultures were reported in 60% and 64% of patients, respectively, and 38% reported both. The agreement rate between corneal and CLR culture results was 30% (n = 15/50). LogMAR VA improved over time in patients with positive corneal and CLR cultures (Estimate=-0.19 per 10-day increase, p = 0.002), and in those with negative corneal and positive CLR cultures (Estimate= -0.17 per 10-day increase, p = 0.004). Compared to patients with negative corneal and CLR cultures, there was a trend toward improvement in VA for patients with positive corneal and CLR cultures (Estimate=-0.68, p = 0.068), and those with negative corneal and positive CLR cultures (Estimate= -0.74, p = 0.059), after adjusting for baseline VA.

CONCLUSIONS

Positive CLR cultures are associated with significant improvement in VA over time. These additional cultures can provide guidance on appropriate antimicrobial selection, especially when corneal cultures are negative.

Microbial Keratitis Isolates at a Midwestern Tertiary Eye Care Center

PURPOSE

The aim of the study was to describe the pathogen, antimicrobial susceptibility, and trends over time of microbial keratitis (MK) at a Midwestern tertiary eye center.

METHODS

Patients with MK were identified in the electronic health record from August 2012 to December 2021. Diagnostic laboratory tests with an MK diagnosis were identified and classified as laboratory positive or laboratory negative. Laboratory-positive infections were categorized as bacterial (gram-positive, gram-negative, or acid-fast bacilli), fungal, viral, Acanthamoeba , or polymicrobial. Antimicrobial susceptibilities were obtained. Trends over time were assessed using linear regression.

RESULTS

Of 3288 patients with MK identified, 1012 (30.8%) had laboratory tests performed. Laboratory-positive infections (n = 499, 49.3%) were bacterial in 73.5% (n = 367) of cases, fungal in 7.8% (n = 39), viral in 1.6% (n = 8), Acanthamoeba in 1.4% (n = 7), and polymicrobial in 15.6% (n = 78). Of bacterial infections, 70% (n = 257) were gram-positive, with coagulase-negative Staphylococcus (CoNS; 31%) and Staphylococcus aureus ( S. aureus ; 23%) as the most common pathogens. Bacteria were acid-fast bacilli in 1.9% (n = 7) of cases and gram-negative in 28.1% (n = 103), with Pseudomonas aeruginosa as the predominant pathogen (47.7%). S. aureus showed antibiotic resistance from 0% (vancomycin and gentamicin) to 50% (erythromycin); CoNS from 0% (vancomycin, gentamicin, and moxifloxacin) to 64% (erythromycin). The rate of laboratory-negative MK significantly increased over time (slope estimate = 2.1% per year, P = 0.034). Rates of bacterial, fungal, viral, Acanthamoeba , and polymicrobial infections were stable over time (all slope P > 0.05).

CONCLUSIONS

Bacterial keratitis accounted for most MK cases. Gram-positive bacteria were the most common isolates. CoNS and S. aureus were universally susceptible to vancomycin. Rates of MK infection types were stable over time.

Quantifying Clinicians' Diagnostic Uncertainty When Making Initial Treatment Decisions for Microbial Keratitis

PURPOSE

There is a need to understand physicians' diagnostic uncertainty in the initial management of microbial keratitis (MK). This study aimed to understand corneal specialists' diagnostic uncertainty by establishing risk thresholds for treatment of MK that could be used to inform a decision curve analysis for prediction modeling.

METHODS

A cross-sectional survey of corneal specialists with at least 2 years clinical experience was conducted. Clinicians provided the percentage risk at which they would always or never treat MK types (bacterial, fungal, herpetic, and amoebic) based on initial ulcer sizes and locations (<2 mm 2 central, <2 mm 2 peripheral, and >8 mm 2 central).

RESULTS

Seventy-two of 99 ophthalmologists participated who were 50% female with an average of 14.7 (SD = 10.1) years of experience, 60% in academic practices, and 38% outside the United States. Clinicians reported they would "never" and "always" treat a <2 mm 2 central MK infection if the median risk was 0% and 20% for bacterial (interquartile range, IQR = 0-5 and 5-50), 4.5% and 27.5% for herpetic (IQR = 0-10 and 10-50), 5% and 50% for fungal (IQR = 0-10 and 20-75), and 5% and 50.5% for amoebic (IQR = 0-20 and 32-80), respectively. Mixed-effects models showed lower thresholds to treat larger and central infections ( P < 0.001, respectively), and thresholds to always treat differed between MK types for the United States ( P < 0.001) but not international clinicians.

CONCLUSIONS

Risk thresholds to treat differed by practice locations and MK types, location, and size. Researchers can use these thresholds to understand when a clinician is uncertain and to create decision support tools to guide clinicians' treatment decisions.

Epidemiological and microbiological profiles of microbial keratitis in a tertiary eye center in Eastern India (Bihar)

Purpose

To determine the demography, risk factors, and causative organisms of microbial keratitis (MK) in Bihar, an eastern state of India.

Design

Retrospective study.

Methods

We reviewed the demographic, clinical, and microbiological data of 2303 patients with MK (non-viral) presenting between January 2019 and December 2022.

Results

This study revealed a predominance of males (65.0%) compared to females (34.9%), with a mean age of 48.4 ± 16.5 years. The majority of patients (63.1%) presented after 2 weeks from the onset of symptoms. The most common risk factor observed was corneal injury (58.1%), followed by ocular surface diseases (13.6%) and diabetes mellitus (13.3%). The majority of patients (73.16%) were involved in agriculture. Prior to presentation, almost all patients (92%) had received topical antibiotics. Unsupervised use of topical corticosteroids was observed in 29.2% of the patients for the median duration of 3 days (odds ratio, 0.17). At presentation, the median size of corneal ulcers was 5 mm, the best-corrected visual acuity was less than 20/400 in 51.4% of patients, and corneal perforation was in 14% of patients. The smear and culture positivity rate were 75.4% and 47.9%, respectively. The common causative organism was fungus (48.8%), followed by bacteria (17.4%). Aspergillus spp. and Staphylococcus spp. were the most commonly identified organisms; a quarter of the patients (24.5%) remained unidentified. All bacteria showed good sensitivity to vancomycin.

Conclusion

MK is a significant cause of ocular morbidity in Bihar. The knowledge of epidemiology, risk factors, and microbiological profiles of MK can provide a valuable approach to disease prevention, diagnosis, and management.

Updates in Diagnostic Imaging for Infectious Keratitis: A Review

Infectious keratitis (IK) is among the top five leading causes of blindness globally. Early diagnosis is needed to guide appropriate therapy to avoid complications such as vision impairment and blindness. Slit lamp microscopy and culture of corneal scrapes are key to diagnosing IK. Slit lamp photography was transformed when digital cameras and smartphones were invented. The digital camera or smartphone camera sensor's resolution, the resolution of the slit lamp and the focal length of the smartphone camera system are key to a high-quality slit lamp image. Alternative diagnostic tools include imaging, such as optical coherence tomography (OCT) and in vivo confocal microscopy (IVCM). OCT's advantage is its ability to accurately determine the depth and extent of the corneal ulceration, infiltrates and haze, therefore characterizing the severity and progression of the infection. However, OCT is not a preferred choice in the diagnostic tool package for infectious keratitis. Rather, IVCM is a great aid in the diagnosis of fungal and Acanthamoeba keratitis with overall sensitivities of 66-74% and 80-100% and specificity of 78-100% and 84-100%, respectively. Recently, deep learning (DL) models have been shown to be promising aids for the diagnosis of IK via image recognition. Most of the studies that have developed DL models to diagnose the different types of IK have utilised slit lamp photographs. Some studies have used extremely efficient single convolutional neural network algorithms to train their models, and others used ensemble approaches with variable results. Limitations of DL models include the need for large image datasets to train the models, the difficulty in finding special features of the different types of IK, the imbalance of training models, the lack of image protocols and misclassification bias, which need to be overcome to apply these models into real-world settings. Newer artificial intelligence technology that generates synthetic data, such as generative adversarial networks, may assist in overcoming some of these limitations of CNN models.

Artificial Intelligence and Infectious Keratitis: Where Are We Now?

Infectious keratitis (IK), which is one of the most common and catastrophic ophthalmic emergencies, accounts for the leading cause of corneal blindness worldwide. Different pathogens, including bacteria, viruses, fungi, and parasites, can cause IK. The diagnosis and etiology detection of IK pose specific challenges, and delayed or incorrect diagnosis can significantly worsen the outcome. Currently, this process is mainly performed based on slit-lamp findings, corneal smear and culture, tissue biopsy, PCR, and confocal microscopy. However, these diagnostic methods have their drawbacks, including experience dependency, tissue damage, cost, and time consumption. Diagnosis and etiology detection of IK can be especially challenging in rural areas or in countries with limited resources. In recent years, artificial intelligence (AI) has opened new windows in medical fields such as ophthalmology. An increasing number of studies have utilized AI in the diagnosis of anterior segment diseases such as IK. Several studies have demonstrated that AI algorithms can diagnose and detect the etiology of IK accurately and fast, which can be valuable, especially in remote areas and in countries with limited resources. Herein, we provided a comprehensive update on the utility of AI in IK.

Whole Corneal Descemetocele

Background and Objectives: To report a case of microbial keratitis complicated by severe corneal melting and whole corneal descemetocele. Methods: A 72-year-old male farmer presented with a right corneal ulcer involving nearly the entire cornea, which was almost completely melted down with the remaining Descemet's membrane (DM). The pupil area was filled with melted necrotic material, with the intraocular lens partially protruding from the pupil and indenting the DM. Corneal optical coherence tomography (OCT) examination revealed a corneal thickness of 37 µm that was attached to its back surface, with the iris and a part of the intraocular lens (IOL) protruding through the pupil. The patient was hospitalized and treated with local and systemic antibiotics until control of the inflammation was achieved. Corneoscleral transplantation plus excision/transplantation of the corneal limbus were performed, and the entire corneal limbus was lamellarly incised. After completely suturing all around the transplanted corneoscleral graft, the anterior chamber was formed. Postoperative treatment included local antibiotics, anti-inflammatory drugs, and cycloplegic drops. Results: There was no recurrence of infection, and the corneal epithelium gradually regenerated and covered the whole graft. Visual acuity was light perception at 6 months after the surgery. The patient was satisfied that the globe was preserved and did not wish to undergo any further treatment. Conclusions: Corneoscleral transplantation is preferred for the treatment of large-sized descemetoceles with active microbial keratitis and extensive infiltrates, especially in cases where the whole cornea has transformed into a large cyst.

Effects of In Vitro Combination of Nitric Oxide Donors and Hypochlorite on Acanthamoeba castellanii Viability

Purpose

To investigate the combined anti-Acanthamoeba effects of nitric oxide (NO) donors and hypochlorite to maximize amoebicidal outcomes while minimizing damage to human corneal epithelial cells (HCECs).

Methods

Acanthamoeba castellanii and primary cultured HCECs and keratocytes were treated with sodium hypochlorite (NaOCl), NO donors (sodium nitroprusside [SNP] and sodium nitrite [NaNO2]), or a combination of hypochlorite and NO donors. The viability of A. castellanii, HCECs, and keratocytes was assessed. Minimal inhibitory concentration (MIC) and fractional inhibitory concentration of NaOCl and NO donors were determined. The activation of mammalian targets of rapamycin (mTOR) and ERK and the expression of nitrite reductase and Nrf2 were assessed in HCECs using Western blot analysis. The cysticidal effects of combined NaOCl and NO donors were also evaluated.

Results

A dose-dependent toxicity was observed in A. castellanii, HCECs, and keratocytes when treated with NaOCl and SNP. The range of tested NaNO2 concentrations showed no significant toxicity to HCECs; however, dose-dependent toxicity to A. castellanii was observed. The MIC of NaOCl against HCECs and A. castellanii was 8.0 mg/mL. The MIC of NaNO2 and SNP was 500 mM and 10 mM in both HCECs and A. castellanii, respectively. Weak attenuation of the mTOR and ERK phosphorylation was observed and Nrf2 expression decreased slightly after exposure of HCECs to 2.0 mg/mL NaOCl. For the combination treatment, NaOCl (0.125 mg/mL) was selected based on the safety of HCECs and the toxicity of A. castellanii. A more potent anti-Acanthamoeba effect and HCEC toxicity were observed when NaOCl was combined with SNP rather than NaNO2.

Conclusions

Combined NaOCl and NO donors had a stronger anti-Acanthamoeba effect compared to either drug alone.

Translational Relevance

This study demonstrates that the combined use of various drugs for the treatment of Acanthamoeba infection can enhance the anti-Acanthamoeba effect while minimizing the toxicity of the individual drug.

The Epidemiological Profile and Predisposing Factors of Microbial Keratitis Over a 10-Year Period at a Tertiary Hospital in Central Saudi Arabia

PURPOSE

To evaluate the demographic and predisposing factors and clinical presentation of microbial keratitis (MK) patients over 10 years at a tertiary hospital in central Saudi Arabia.

METHOD

In 2020, a retrospective review of data from clinical and pathology departments from 2010 to 2019 was conducted. Demography includes age, gender, residence, and the risk factor of microbial keratitis, clinical features, and organism profile as number and percentage.

RESULT

We reviewed 181 eyes of 179 patients with microbial keratitis. The mean age was 40.1 years. Contact lens usage (55; 30%), ocular trauma (30; 16.5%), and ocular surface diseases (42; 23.2%) were the main predisposing factors. Hypopyon was noted in 60 (33%) eyes, impaired vision at presentation was observed in 78 (43%) eyes, and endophthalmitis with microbial keratitis was noted in eight (4.4%) eyes at presentation. Ninety-eight (54,1%) cases were culture positive, while gram-positive organisms were seen in 50 (27.6%) eyes, gram-negative organisms in 35 (19.3%) patients, and fungi in 13 (7.2%) patients. Microbial keratitis was central in 67 (37%), paracentral in 94 (52%), and peripheral in 20 (11.3%) patients. All instances of fungal keratitis occurred in the eyes of men who work in the agriculture field.

CONCLUSION

Standard operating procedures to manage microbial keratitis at primary and secondary eye care levels are recommended. Health promotion to prevent trauma, appropriate use of contact lens, and early treatment could prevent the incidence of microbial keratitis.

A 7-year review of clinical characteristics, predisposing factors and outcomes of post-keratoplasty infectious keratitis: the Nottingham infectious keratitis study

Background/objectives

Post-keratoplasty infectious keratitis (PKIK) is a unique sight-threatening clinical entity which often poses significant therapeutic challenges. This study aimed to examine the clinical presentation, risk factors, management, and clinical outcomes of PKIK.

Methods

This was a retrospective study of all patients who presented to the Queen's Medical Centre, Nottingham, with PKIK between September 2015 and August 2022 (a 7-year period). Relevant data on types of keratoplasty, clinical presentations, causative microorganisms, management, and outcome were analyzed.

Results

Forty-nine PKIK cases, including four cases of interface infectious keratitis, were identified during the study period. The most common graft indications for PKP, DALK and EK were failed grafts (9, 37.5%), keratoconus (6, 54.5%) and Fuchs endothelial corneal dystrophy (FECD; 8, 57.1%), respectively. Staphylococcus spp. were the most commonly identified organisms (15, 50.0%). Bullous keratopathy (18, 36.7%), ocular surface disease (18, 36.7%), and broken/loose sutures (15, 30.6%) were the most common risk factors. Concurrent use of topical steroids was identified in 25 (51.0%) cases. Of 31 functioning grafts at presentation, 12 (38.7%) grafts failed at final follow-up with 15 (48.4%) patients retaining a CDVA of ≥1.0 logMAR. The overall estimated 5-year survival rate post-PKIK was 55.9% (95% CI, 35.9%-75.9%), with DALK having the highest survival rate [63.6% (95% CI, 28.9%-98.3%)], followed by EK [57.1% (95% CI, 20.4%-93.8%)] and PKP [52.7% (95% CI, 25.1%-80.3%)], though no statistical difference was observed (p=0.48).

Conclusions

PKIK represents an important cause of IK and graft failure. Bullous keratopathy, OSD and suture-related complications are the commonest risk factors, highlighting the potential benefit of prophylactic topical antibiotics (for unhealthy ocular surface) and early suture removal (where possible) in reducing the risk of PKIK. Graft survival may be higher in lamellar keratoplasty following PKIK but larger studies are required to elucidate this observation.

Managing Corneal Infections: Out with the old, in with the new?

There have been multiple reports of eye infections caused by antibiotic-resistant bacteria, with increasing evidence of ineffective treatment outcomes from existing therapies. With respect to corneal infections, the most commonly used antibiotics (fluoroquinolones, aminoglycosides, and cephalosporines) are demonstrating reduced efficacy against bacterial keratitis isolates. While traditional methods are losing efficacy, several novel technologies are under investigation, including light-based anti-infective technology with or without chemical substrates, phage therapy, and probiotics. Many of these methods show non-selective antimicrobial activity with potential development as broad-spectrum antimicrobial agents. Multiple preclinical studies and a limited number of clinical case studies have confirmed the efficacy of some of these novel methods. However, given the rapid evolution of corneal infections, their treatment requires rapid institution to limit the impact on vision and prevent complications such as scarring and corneal perforation. Given their rapid effects on microbial viability, light-based technologies seem particularly promising in this regard.

Corneal Culture and Antibiotic Susceptibility Results for Microbial Keratitis in the Mid-Atlantic Region of the United States, 2016 to 2020

OBJECTIVE

To examine the microbial distribution and antimicrobial susceptibility of culture-positive microbial keratitis at a large tertiary referral center in the mid-Atlantic region of the United States.

METHODS

Retrospective review of culture-positive microbial keratitis cases at the Wilmer Eye Institute from 2016 through 2020.

RESULTS

Of the 474 culture-positive microbial keratitis cases, most were bacterial (N=450, 94.9%), followed by fungal (N=48, 10.1%) and Acanthamoeba keratitis (N=15, 3.1%). Of the 450 bacterial isolates, 284 (69.5%) were gram-positive organisms, whereas 157 (28.4%) were gram-negative organisms. The most common bacterial species isolated was coagulase-negative Staphylococcus spp (N=154, 24.8%), and the most common gram-negative isolate was Pseudomonas aeruginosa (N=76, 12.3%). Among fungi, the most common isolates were Candida (N=25, 45.4%), whereas Fusarium (N=6, 10.9%) and Aspergillus (N=3, 5.5%) were less common. Of the 217 bacterial isolates tested for erythromycin susceptibility, 121 (55.7%; ∼60% of coagulase-negative staphylococci and corynebacteria tested) showed resistance to erythromycin.

CONCLUSIONS

Microbial keratitis in the Baltimore Mid-Atlantic region of the United States is most commonly caused by bacteria, with fungi and acanthamoeba being less common. Gram-positive bacterial infections predominate. Among fungal keratitis cases, Candida species are more commonly encountered than are filamentous species. Use of erythromycin as infection prophylaxis should be reexamined. Findings from our study may guide empiric treatment in this geographic region.

The effect of social determinants of health on severity of microbial keratitis presentation at a tertiary eye care hospital in Southern India

Purpose

Understanding the association between social determinants of health (SDoHs) and microbial keratitis (MK) can inform underlying risk for patients and identify risk factors associated with worse disease, such as presenting visual acuity (VA) and time to initial presentation.

Methods

This was a cross-sectional study was conducted with patients presenting with MK to the cornea clinic at a tertiary care hospital in Madurai, India. Patient demographics, SDoH survey responses, geographic pollution, and clinical features at presentation were collected. Descriptive statistics, univariate analysis, multi-variable linear regression models, and Poisson regression models were utilized.

Results

There were 51 patients evaluated. The mean age was 51.2 years (SD = 13.3); 33.3% were female and 55% did not visit a vision center (VC) prior to presenting to the clinic. The median presenting logarithm of the minimum angle of resolution (logMAR) VA was 1.1 [Snellen 20/240, inter-quartile range (IQR) = 20/80 to 20/4000]. The median time to presentation was 7 days (IQR = 4.5 to 10). The average particulate matter 2.5 (PM2.5) concentration, a measure of air pollution, for the districts from which the patients traveled was 24.3 μg/m3 (SD = 1.6). Age- and sex-adjusted linear regression and Poisson regression results showed that higher levels of PM2.5 were associated with 0.28 worse presenting logMAR VA (Snellen 2.8 lines, P = 0.002). Patients who did not visit a VC had a 100% longer time to presentation compared to those who did (incidence rate ratio = 2.0, 95% confidence interval = 1.3-3.0, P = 0.001).

Conclusion

Patient SDoH and environmental exposures can impact MK presentation. Understanding SDoH is important for public health and policy implications to mitigate eye health disparities in India.

Incidence of Corneal Adverse Events in Children Wearing Soft Contact Lenses

OBJECTIVES

There is increasing interest in fitting children with soft contact lenses, in part due to the increase in prescribing of designs to slow the progression of myopia. This literature review summarizes large prospective and retrospective studies that include data on the incidence of microbial keratitis and corneal infiltrative events (CIEs) in children wearing soft contact lenses.

METHODS

Peer-reviewed prospective and retrospective studies that report contact lens-related complications in children with at least one year of wear and at least 100 patient years of wear were identified.

RESULTS

Seven prospective studies published between 2004 and 2022 were identified representing 3,752 patient years of wear in 1,756 children, nearly all of whom were fitted at age 12 years or younger. Collectively, they report one case of microbial keratitis and 53 CIEs, of which 16 were classified as symptomatic. The overall incidence of microbial keratitis was 2.7 per 10,000 patient years (95% CI: 0.5-15), and the incidence of symptomatic CIEs was 42 per 10,000 patient years (95% CI: 26-69). Two retrospective studies were identified representing 2,545 patient years of wear in 1,025 children, fitted at age 12 years or younger. One study reports two cases of microbial keratitis giving an incidence of 9.4 per 10,000 patient years (95% CI: 0.5-15).

CONCLUSIONS

Accurate classification of CIEs is challenging, particularly in retrospective studies. The incidence of microbial keratitis in children wearing soft lenses is no higher than in adults, and the incidence of CIEs seems to be markedly lower.

Survey-Based Estimation of Corneal Complications Associated with Scleral Lens Wear

ABSTRACT

The benefits of scleral lens (SL) wear have been described in cross-sectional and retrospective studies; however, the frequency of complications associated with SL wear has not, to the best of our knowledge, been determined. From a survey of SL practitioners, we estimated the period prevalence over 1 year of corneal complications that required SL wearers to discontinue lens wear. In a sample of 72,605 wearers, SL wear was discontinued for the following complications: corneal edema, 1.2%; corneal neovascularization, 0.53%; microbial keratitis, 0.45%; and limbal stem cell deficiency, 0.20%. This study design allowed for calculation of period prevalence of these complications rather than complication incidence rates. Information presented in this report may be useful in clinical decision-making and for future study design.

Prediction of Visual Acuity in Patients With Microbial Keratitis

PURPOSE

The purpose of this study was to predict visual acuity (VA) 90 days after presentation for patients with microbial keratitis (MK) from data at the initial clinical ophthalmic encounter.

METHODS

Patients with MK were identified in the electronic health record between August 2012 and February 2021. Random forest (RF) models were used to predict 90-day VA < 20/40 [visual impairment (VI)]. Predictors evaluated included age, sex, initial VA, and information documented in notes at presentation. Model diagnostics are reported with 95% confidence intervals (CIs) for area under the curve (AUC), misclassification rate, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV).

RESULTS

One thousand seven hundred ninety-one patients were identified. The presenting logMAR VA was on average 0.86 (Snellen equivalent and standard deviation = 20/144 ± 12.6 lines) in the affected or worse eye, and 43.6% with VI. VI at 90-day follow-up was present in the affected eye or worse eye for 26.9% of patients. The RF model for predicting 90-day VI had an AUC of 95% (CI: 93%-97%) and a misclassification rate of 9% (7%-12%). The percent sensitivity, specificity, PPV, and NPV were 86% (80%-91%), 92% (89%-95%), 81% (74%-86%), and 95% (92%-97%), respectively. Older age, worse presenting VA, and more mentions of "penetrating keratoplasty" and "bandage contact lens" were associated with increased probability of 90-day VI, whereas more mentions of "quiet" were associated with decreased probability of 90-day VI.

CONCLUSIONS

RF modeling yielded good sensitivity and specificity to predict VI at 90 days which could guide clinicians about the risk of poor vision outcomes for patients with MK.

Local Ugandan Production of Stable 0.2% Chlorhexidine Eye Drops

Purpose

The purpose of this study was to develop a protocol to prepare buffered chlorhexidine (CHX) eye drops (0.2% w/v) in the United Kingdom that can be reproduced at a production facility in Uganda. Buffered CHX eye drops can prevent CHX degradation and improve ocular tolerability during the treatment of fungal keratitis.

Methods

Buffered CHX eye drops in amber glass containers were prepared using sodium acetate buffer at pH 5.90 to 6.75. Two commercial CHX solutions and CHX in water were used as controls. Eye drops were stored at 40°C (70% humidity, 21 months) in the United Kingdom and at ambient temperature in Uganda (30 months). High-performance liquid chromatography was used to determine CHX stability over time, and pH was monitored. Sterility was achieved using an autoclave (121°C, 15 minutes) and water bath (100°C, 30 minutes).

Results

The pH of acetate-buffered CHX eye drops did not change over 21 months at 40°C or at ambient temperature (30 months), whereas the pH of the unbuffered aqueous CHX displayed significant fluctuations, with an increase in acidity. The CHX concentration remained the same in both buffered and unbuffered eye-drop solutions. Eye drops sterilization was successful using an autoclave and a water bath.

Conclusions

Stable, sterile, buffered CHX eye drops (pH 6.75) were successfully prepared first in the United Kingdom and then reproducibly in Uganda. This eye drops can be prepared in a hospital or pharmacy setting with limited resources, thus providing a cost-effective treatment for fungal keratitis.

Translational Relevance

A protocol has been developed to prepare buffered CHX eye drops in low- and middle-income countries to treat fungal keratitis.

Complete Recovery of Acanthamoeba Motility among Surviving Organisms after Contact Lens Care Disinfection

Acanthamoeba keratitis is a sight-threatening infection of the cornea which is extremely challenging to treat. Understanding this organism's responses during contact lens contact and disinfection could enhance our understanding of how Acanthamoebae colonize contact lens cases, better inform us on contact lens care solution (CLC) efficacy, and help us better understand the efficacy required of CLC products. To explore this gap in knowledge, we used Acanthamoeba ATCC 30461 and ATCC 50370 trophozoites to examine Acanthamoeba behavior during and after CLC disinfection. Amoebae were added to sterile aluminum flow cells and flow cell solutions were changed to Ringer's solution (control), or one of four CLCs based on biocides (PHMB, PAPB/Polyquad, Polyquad/Aldox, or Polyquad/Alexidine) for 6 h. Each flow cell solution was then changed to axenic culture media (AC6) for 12 h to determine the behavior of amoebae following disinfection. Distance, speed, and displacement were calculated for each organism. As compared to the control of one-quarter Ringer's solution, each CLC significantly impacted Acanthamoeba motility in both the CLC and AC6 conditions. However, the amoebae challenged with the PHMB CLC traveled a significantly greater total distance than with the other three CLCs, indicating differences in effectiveness between biocides. Furthermore, amoebae regaining motility post-disinfection by CLCs were observed to travel considerable distances and thus could be considered dangerous to ocular health. We determined that while all CLCs produced a substantial or complete cessation of movement vs. the control condition during disinfection, those which relied on the Polyquad biocides were the most effective, and that any amoebae which survived disinfection were able to recover motility. Future examinations of these findings should include direct correlations between motility and viability, and how infectivity and motility may be related.

Presumed Microbial Keratitis Cases Resulting in Evisceration and Enucleation in Sydney, Australia

PURPOSE

Describe presumed microbial keratitis cases resulting in evisceration/enucleation from 2012 to 2016 in Sydney, Australia.

METHODS

A retrospective case review included 33 patients. Cases were identified from pathology and hospital coding data. Sociodemographic and clinical details were collated.

RESULTS

Mean age was 79 years (range: 38-100 years), and 64% female. There were 30 eviscerations and 3 enucleations, at a median time of 8 days (range: 1-270 days) due to endophthalmitis (n = 15, 45%). Major ocular associated factors included topical corticosteroid use in 12 patients (36%), exposure keratopathy in 4 (12%), ectropion in 3 (9%), degenerative corneal disease in 3 (9%), and corneal graft in 2 (6%). Pseudomonas aeruginosa was the most common isolate with no reports of antimicrobial resistance.

CONCLUSIONS

Educating elderly patients with a history of topical corticosteroid use, corneal or ocular surface disease about prompt hospital presentation and treatment of microbial keratitis may decrease the probability of losing the eye.

Deep Learning Approach in Image Diagnosis of Pseudomonas Keratitis

This investigation aimed to explore deep learning (DL) models' potential for diagnosing Pseudomonas keratitis using external eye images. In the retrospective research, the images of bacterial keratitis (BK, n = 929), classified as Pseudomonas (n = 618) and non-Pseudomonas (n = 311) keratitis, were collected. Eight DL algorithms, including ResNet50, DenseNet121, ResNeXt50, SE-ResNet50, and EfficientNets B0 to B3, were adopted as backbone models to train and obtain the best ensemble 2-, 3-, 4-, and 5-DL models. Five-fold cross-validation was used to determine the ability of single and ensemble models to diagnose Pseudomonas keratitis. The EfficientNet B2 model had the highest accuracy (71.2%) of the eight single-DL models, while the best ensemble 4-DL model showed the highest accuracy (72.1%) among the ensemble models. However, no statistical difference was shown in the area under the receiver operating characteristic curve and diagnostic accuracy among these single-DL models and among the four best ensemble models. As a proof of concept, the DL approach, via external eye photos, could assist in identifying Pseudomonas keratitis from BK patients. All the best ensemble models can enhance the performance of constituent DL models in diagnosing Pseudomonas keratitis, but the enhancement effect appears to be limited.

Management of Filamentous Fungal Keratitis: A Pragmatic Approach

Filamentous fungal infections of the cornea known as filamentous fungal keratitis (FK) are challenging to treat. Topical natamycin 5% is usually first-line treatment following the results of several landmark clinical trials. However, even when treated intensively, infections may progress to corneal perforation. Current topical antifungals are not always effective and are often unavailable. Alternatives topical therapies to natamycin include voriconazole, chlorhexidine, amphotericin B and econazole. Surgical therapy, typically in the form of therapeutic penetrating keratoplasty, may be required for severe cases or following corneal perforation. Alternative treatment strategies such as intrastromal or intracameral injections of antifungals may be used. However, there is often no clear treatment strategy and the evidence to guide therapy is often lacking. This review describes the different treatment options and their evidence and provides a pragmatic approach to the management of fungal keratitis, particularly for clinicians working in tropical, low-resource settings where fungal keratitis is most prevalent.

Clinical differentiation of Pythium keratitis from fungal keratitis and development of a scoring system

Purpose

To differentiate Pythium keratitis from fungal keratitis using clinical signs, to explore usefulness of various signs as diagnostic prognosticators, and develop a clinical scoring system.

Methods

A retrospective review of medical records and archived clinical photographs of patients with culture-positive Pythium keratitis and hyaline filamentous fungal keratitis was conducted at a tertiary eye institute to explore characteristics of ulcers that may aid diagnosis.

Results

Full-thickness corneal stromal keratitis (P = 0.055), a dry ulcer surface (P = 0.010), tentacles (P < 0.0001), intrastromal dots (P < 0.0001), ring infiltrates (P = 0.024), reticular patterns (P < 0.0001), and peripheral furrows (P < 0.0001) were clinical signs associated with Pythium keratitis. Multiple regression analysis identified tentacles (odds ratio: 24.1, 95% confidence interval (CI): 3.8-158.1, P = 0.001) and peripheral furrows (odds ratio: 60.6, 95% CI: 5.1-712.3, P = 0.001) as independent diagnostic prognosticators for Pythium keratitis. The positive and negative likelihood ratios of a dry ulcer surface, tentacles, intrastromal dots, ring infiltrates, reticular patterns, and peripheral furrows predicting Pythium keratitis were 1.6, 13.6, 17.9, 4.3, 30.7, 15.3 and 0.4, 0.4, 0.7, 0.9, 0.6 and 0.8, respectively. The presence of two or more of these clinical signs (excluding a dry ulcer surface) had a sensitivity of 55.6% and a false positive rate of 1.4%.

Conclusion

Tentacles, intrastromal dots, ring infiltrates, reticular patterns, and peripheral furrows are clinical signs to be considered for the diagnosis of Pythium keratitis and the presence of two or more signs has a very low false positive rate.

Unusual Presentation of Pythium Keratitis as Peripheral Ulcerative Keratitis: Clinical Dilemma

PURPOSE

To describe the clinical picture and outcome of a case of Pythium keratitis, presenting as peripheral ulcerative keratitis (PUK).

CASE SUMMARY

A 54- year- old male presented to the clinic with a PUK in the right eye. Systemic investigations were performed to rule out associated collagen vascular disorders. Microbiological examination of corneal scrapings was performed to rule out secondary infection which revealed gram positive cocci on Gram stain. There was no growth of any organism on culture. Topical vancomycin 5% and ciprofloxacin 0.3% were started initially. On regular follow-up, there was worsening of clinical signs. Topical and oral corticosteroids were further added. Due to progressive worsening of infiltrate size and corneal perforation, therapeutic penetrating keratoplasty was performed. Pythium insidiosum (confirmed by DNA sequencing and zoospore formation) was grown from excised corneal button and the histopathology revealed filaments suggestive of Pythium species.

CONCLUSION

This case describes the uncommon manifestation of Pythium insidiosum keratitis presenting as peripheral ulcerative keratitis.

Acremonium keratitis: Risk factors, clinical characteristics, management, and outcome in 65 cases

Purpose

To study the risk factors, clinical presentation, management options, and outcomes in cases of culture-proven Acremonium keratitis.

Methods

Medical and microbiology records of culture-proven Acremonium keratitis from Jan 2007 to Dec 2019 at a tertiary eye care center were reviewed. Details of clinical findings on each visit and operating notes were reviewed from the medical records. All cases were subjected to corneal scraping at the first visit for microbiological investigation consisting of direct smear examination and culture. Topical natamycin 5% was the mainstay of medical treatment. Surgical treatment was considered for nonresponding patients.

Results

During the 13-year study period, 65 cases of culture-proven Acremonium keratitis were identified out of 1605 cases of fungal keratitis. Trauma was the most common predisposing factor in 32 cases (49.2%). The average area of the corneal stromal infiltrate was 24.8 mm² at the initial presentation. Hypopyon at the time of presentation was evident in 28 (43.1%) cases. Staphylococcus spp. was the most common (n = 22, 33.8%) organism coexistent with Acremonium. Direct microscopy of corneal scraping was positive for fungal filaments in 57/65 (87.6%) cases. Medical management alone was given in 44 patients (67.6%). Age (>50 years) and treatment delay (>15 days) were found to be independent risk factors for the poor final visual outcome (VA <20/60).

Conclusion

When treated early, Acremonium keratitis responds well to medical therapy with currently available topical antifungals. However, advanced and nonresponding cases require surgical intervention for resolution of the infection.

Diagnosis of Fungal Keratitis in Low-Income Countries: Evaluation of Smear Microscopy, Culture, and In Vivo Confocal Microscopy in Nepal

Clinically diagnosing fungal keratitis (FK) is challenging; diagnosis can be assisted by investigations including in vivo confocal microscopy (IVCM), smear microscopy, and culture. The aim of this study was to estimate the sensitivity in detecting fungal keratitis (FK) using IVCM, smear microscopy, and culture in a setting with a high prevalence of FK. In this cross-sectional study nested within a prospective cohort study, consecutive microbial keratitis (MK) patients attending a tertiary-referral eye hospital in south-eastern Nepal between June 2019 and November 2020 were recruited. IVCM and corneal scrapes for smear microscopy and culture were performed using a standardised protocol. Smear microscopy was performed using potassium hydroxide (KOH), Gram stain, and calcofluor white. The primary outcomes were sensitivities with 95% confidence intervals [95% CI] for IVCM, smear microscopy and culture, and for each different microscopy stain independently, to detect FK compared to a composite referent. We enrolled 642 patients with MK; 468/642 (72.9%) were filamentous FK, 32/642 (5.0%) were bacterial keratitis and 64/642 (10.0%) were mixed bacterial-filamentous FK, with one yeast infection (0.16%). No organism was identified in 77/642 (12.0%). Smear microscopy had the highest sensitivity (90.7% [87.9-93.1%]), followed by IVCM (89.8% [86.9-92.3%]) and culture (75.7% [71.8-79.3%]). Of the three smear microscopy stains, KOH had the highest sensitivity (85.3% [81.9-88.4%]), followed by Gram stain (83.2% [79.7-86.4%]) and calcofluor white (79.1% [75.4-82.5%]). Smear microscopy and IVCM were the most sensitive tools for identifying FK in our cohort. In low-resource settings we recommend clinicians perform corneal scrapes for microscopy using KOH and Gram staining. Culture remains an important tool to diagnose bacterial infection, identify causative fungi and enable antimicrobial susceptibility testing.

Artificial intelligence and corneal diseases

PURPOSE OF REVIEW

Artificial intelligence has advanced rapidly in recent years and has provided powerful tools to aid with the diagnosis, management, and treatment of ophthalmic diseases. This article aims to review the most current clinical artificial intelligence applications in anterior segment diseases, with an emphasis on microbial keratitis, keratoconus, dry eye syndrome, and Fuchs endothelial dystrophy.

RECENT FINDINGS

Most current artificial intelligence approaches have focused on developing deep learning algorithms based on various imaging modalities. Algorithms have been developed to detect and differentiate microbial keratitis classes and quantify microbial keratitis features. Artificial intelligence may aid with early detection and staging of keratoconus. Many advances have been made to detect, segment, and quantify features of dry eye syndrome and Fuchs. There is significant variability in the reporting of methodology, patient population, and outcome metrics.

SUMMARY

Artificial intelligence shows great promise in detecting, diagnosing, grading, and measuring diseases. There is a need for standardization of reporting to improve the transparency, validity, and comparability of algorithms.

Antimicrobial Peptide Expression at the Ocular Surface and Their Therapeutic Use in the Treatment of Microbial Keratitis

Microbial keratitis is a common cause of ocular pain and visual impairment worldwide. The ocular surface has a relatively paucicellular microbial community, mostly found in the conjunctiva, while the cornea would be considered relatively sterile. However, in patients with microbial keratitis, the cornea can be infected with multiple pathogens including Staphylococcus aureus, Pseudomonas aeruginosa, and Fusarium sp. Treatment with topical antimicrobials serves as the standard of care for microbial keratitis, however, due to high rates of pathogen resistance to current antimicrobial medications, alternative therapeutic strategies must be developed. Multiple studies have characterized the expression and activity of antimicrobial peptides (AMPs), endogenous peptides with key antimicrobial and wound healing properties, on the ocular surface. Recent studies and clinical trials provide promise for the use of AMPs as therapeutic agents. This article reviews the repertoire of AMPs expressed at the ocular surface, how expression of these AMPs can be modulated, and the potential for harnessing the AMPs as potential therapeutics for patients with microbial keratitis.

Deep Learning for Discrimination Between Fungal Keratitis and Bacterial Keratitis: DeepKeratitis

PURPOSE

Microbial keratitis is an urgent condition in ophthalmology that requires prompt treatment. This study aimed to apply deep learning algorithms for rapidly discriminating between fungal keratitis (FK) and bacterial keratitis (BK).

METHODS

A total of 2167 anterior segment images retrospectively acquired from 194 patients with 128 patients with BK (1388 images, 64.1%) and 66 patients with FK (779 images, 35.9%) were used to develop the model. The images were split into training, validation, and test sets. Three convolutional neural networks consisting of VGG19, ResNet50, and DenseNet121 were trained to classify images. Performance of each model was evaluated using precision (positive predictive value), sensitivity (recall), F1 score (test's accuracy), and area under the precision-recall curve (AUPRC). Ensemble learning was then applied to improve classification performance.

RESULTS

The classification performance in F1 score (95% confident interval) of VGG19, DenseNet121, and RestNet50 was 0.78 (0.72-0.84), 0.71 (0.64-0.78), and 0.68 (0.61-0.75), respectively. VGG19 also demonstrated the highest AUPRC of 0.86 followed by RestNet50 (0.73) and DenseNet (0.60). The ensemble learning could improve performance with the sensitivity and F1 score of 0.77 (0.81-0.83) and 0.83 (0.77-0.89) with an AUPRC of 0.904.

CONCLUSIONS

Convolutional neural network with ensemble learning showed the best performance in discriminating FK from BK compared with single architecture models. Our model can potentially be considered as an adjunctive tool for providing rapid provisional diagnosis in patients with microbial keratitis.

Update on indications, complications, and outcomes of scleral contact lenses

Background

The role of scleral contact lenses (SCLs) has increasingly expanded since the first lens was fitted more than a century ago. While it was initially prescribed for the management of severely compromised corneas, the indications for modern SCL use have expanded to include less severe diseases. In this review, we aimed to provide an up-to-date overview of the current indications, complications, and outcomes for the various types of SCLs.

Methods

In this narrative review, we thoroughly searched the PubMed/MEDLINE database for literature published from January 1980 to November 2021. Only relevant up-to-date English references were included. Furthermore, the figures in this manuscript were derived from our unit's patient documentation.

Results

Currently, SCLs can successfully be used to manage ocular surface diseases, visually rehabilitate irregular corneas, and correct irregular refractive errors. Although newer materials have yielded the same visual outcomes with fewer complications, these consequences still occur in approximately one-third of contact lens wearers, including difficulties in insertion and/or removal, discomfort or pain, and developing either halos, blurriness, or haze. Even though most of these complications are minor and can be easily treated, a good practice is essential to avoid sight-threatening complications such as microbial keratitis.

Conclusions

SCLs are indispensable in ophthalmic clinics. The development of better-quality SCLs has increased the number of indications and improved the achievable visual rehabilitation. The future of developing improvements in SCL design, materials, and fit, and the expansion of their indication range is promising.

Comparison of Culture-Positive and -Negative Microbial Keratitis

Objectives:

To evaluate and compare the risk factors, presenting features, and outcomes of patients with culture-positive and culturenegative microbial keratitis (MK) who presented to a tertiary referral center.

Materials and Methods:

We conducted a retrospective review of the medical records of 314 patients who were diagnosed with MK in our clinic between 2012 and 2019.

Results:

Among 314 patients, 142 had positive cultures (45.2%). The mean ages of the culture-positive and -negative patients at the time of diagnosis were 51.39±21.31 (range, 14-90) years and 56.68±21.34 (7-94) years, respectively (p=0.028). The mean best corrected visual acuity (BCVA) of the culture-positive and -negative patients were1.74±1.25 (0-3.1) LogMAR and 1.91±1.23 (0-3.1) LogMAR prior to treatment and increased to 1.21±1.30 (0-3.1) LogMAR and 1.27± 1.29 (0-3.1) LogMAR at last visit, respectively. There was no statistically significant difference between culture-positive and -negative patients’ BCVA levels at presentation or last visit. Ninety-two patients (64.7%) were infected with bacteria and 50 patients (35.2%) with fungi. The most common pathogen was Pseudomonas aeruginosa (18.3%), followed by Streptococcus pneumoniae (11.2%) and Fusarium spp. (11.2%). Keratitis foci were either centrally or paracentrally located in 105 eyes (73.9%) of culture-positive patients and 149 eyes (86.6%) of culture-negative patients. Multiple foci were present mostly in culture-positive patients (p=0.001). There was no significant difference between the culture-positive and -negative groups in terms of hypopyon presence (p=0.364). The proportion of contact lens (CL) wearers was 33% (n=47) among culturepositive MK patients and 13.3% (n=23) among culture-negative MK patients, respectively (p<0.001). Culture positivity was found to be significantly higher in keratitis associated with CL use (p=0.0001).

Conclusion:

Microbiological analysis and culture evaluation are important steps in order to manage proper treatment in microbial keratitis. Prognosis mostly depends on the infectivity of the microbiological agent.

Microbial Keratitis in Nepal: Predicting the Microbial Aetiology from Clinical Features

Fungal corneal infection (keratitis) is a common clinical problem in South Asia. However, it is often challenging to distinguish this from other aetiologies, such as bacteria or acanthamoeba. In this prospective study, we investigated clinical and epidemiological features that can predict the microbial aetiology of microbial keratitis in Nepal. We recruited patients presenting with keratitis to a tertiary eye hospital in lowland eastern Nepal between June 2019 and November 2020. A structured assessment, including demographics, history, and clinical signs, was carried out. The aetiology was investigated with in vivo confocal microscopy and corneal scrape for microscopy and culture. A predictor score was developed using odds ratios calculated to predict aetiology from features. A fungal cause was identified in 482/642 (75.1%) of cases, which increased to 532/642 (82.9%) when including mixed infections. Unusually, dematiaceous fungi accounted for half of the culture-positive cases (50.6%). Serrated infiltrate margins, patent nasolacrimal duct, raised corneal slough, and organic trauma were independently associated with fungal keratitis (p < 0.01). These four features were combined in a predictor score. The probability of fungal keratitis was 30.1% if one feature was present, increasing to 96.3% if all four were present. Whilst microbiological diagnosis is the "gold standard" to determine the aetiology of an infection, certain clinical signs can help direct the clinician to find a presumptive infectious cause, allowing appropriate treatment to be started without delay. Additionally, this study identified dematiaceous fungi, specifically Curvularia spp., as the main causative agent for fungal keratitis in this region. This novel finding warrants further research to understand potential implications and any trends over time.

Delay in accessing definitive care for patients with microbial keratitis in Nepal

Background

The aim of this study was to describe the health-seeking journey for patients with microbial keratitis (MK) in Nepal and identify factors associated with delay.

Methods

Prospective cohort study where MK patients attending a large, tertiary-referral eye hospital in south-eastern Nepal between June 2019 and November 2020 were recruited. We collected demographic details, clinical history, and examination findings. Care-seeking journey details were captured including places attended, number of journeys, time from symptom onset, and costs. We compared "direct" with "indirect" presenters, analyzing for predictors of delay.

Results

We enrolled 643 patients with MK. The majority (96%) self-referred. "Direct" attenders accounted for only 23.6% (152/643) of patients, the majority of "indirect" patients initially presented to a pharmacy (255/491). Over half (328/643) of all cases presented after at least 7 days. The total cost of care increased with increasing numbers of facilities visited (p < 0.001). Those living furthest away were least likely to present directly (p < 0.001). Factors independently associated with delayed presentation included distance >50 km from the eye hospital [aOR 5.760 (95% CI 1.829-18.14, p = 0.003)], previous antifungal use [aOR 4.706 (95% CI 3.139-5.360)], and two or more previous journeys [aOR 1.442 (95% CI 1.111-3.255)].

Conclusions

Most patients visited at least one facility prior to our institution, with time to presentation and costs increasing with the number of prior journeys. Distance to the eye hospital is a significant barrier to prompt, direct presentation. Based on these findings, improving access to eye care services, strengthening referral networks and encouraging early appropriate treatment are recommended to reduce delay, ultimately improving clinical outcomes.

Multidrug-Resistant Stenotrophomonas maltophilia Keratitis in a Penetrating Keratoplasty Patient

We describe the management of a case of multidrug-resistant Stenotrophomonas maltophilia in a patient who had previously undergone photorefractive keratectomy and subsequent penetrating keratoplasty for Schnyder’s crystalline corneal dystrophy. This pathogen is rare and, in this case, was multi-drug resistant.

Bacterial Keratitis: Similar Bacterial and Clinical Outcomes in Female versus Male New Zealand White Rabbits Infected with Serratia marcescens

PURPOSE

Females and males respond differently to a number of systemic viral infections. Differences between females and males with respect to the severity of keratitis caused by Gram-negative bacteria such as Serratia marcescens are less well established.

METHODS

In this study, we injected female and male New Zealand White rabbit corneas with a keratitis isolate of S. marcescens and evaluated the eyes after 48 hours for a number of clinical and microbiological parameters.

RESULTS

No statistical differences in bacterial burden and corneal scores were recorded between female and male rabbits although there was a non-significant trend toward a higher frequency of female rabbits demonstrating hypopyons.

CONCLUSIONS

This data suggests that for experimental bacterial keratitis studies involving Gram-negative rods, a single sex or mixed group of rabbit is sufficient for evaluating pathology and bacterial burdens. This will reduce the number of animals used for subsequent studies.

Ocular pathogens and antibiotic resistance in microbial keratitis over three years in Harbin, Northeast China

Purpose

Understanding the spectrum of ocular pathogens in a given geographic region is important for devising appropriate practical treatment. Therefore, we examined the pathogen spectrum and antibiotic resistance of microbial keratitis in northeast China.

Methods

In this retrospective observational study, we reviewed the microbiology laboratory records of patients diagnosed with microbial keratitis in a tertiary eye hospital in Harbin, northeast China, between 2017 and 2019, and analysed the pathogen spectrum and antibiotic susceptibility.

Results

We collected 462 specimens, of which 282 exhibited positive cultures. Among these cultures, 257 were bacterial and 25 were fungal. Of the 257 bacterial isolates, 214 (83.27%) were gram positive whereas 43 (16.73%) were gram negative. The most prevalent gram‐positive pathogen was coagulase‐negative staphylococcus (CoNS; 58.37%), followed by Staphylococcus aureus (S. aureus; 20.62%) and Streptococcus pneumoniae (2.33%). Of the gram‐negative bacterial isolates, 10 were Pseudomonas aeruginosa (3.89%). The most frequently detected ocular pathogens from fungal isolates were Fusarium species (40%). We also found more culture‐positive cases of bacterial keratitis in summer. Overall, 16.98% S. aureus and 64.00% CoNS isolates were methicillin resistant. These methicillin‐resistant bacteria were also more likely to be resistant to other antibiotics, with multidrug resistance found in 77.78% methicillin‐resistant S. aureus and 90.63% methicillin‐resistant CoNS. However, all gram‐positive isolates were sensitive to vancomycin and linezolid.

Conclusion

Coagulase‐negative staphylococcus are the most common ocular pathogens in northeast China. We also show the prevalence of methicillin resistance and concurrent multidrug resistance among staphylococcal isolates. Monitoring the patterns of antimicrobial resistance could help in the management selection.

An Evaluation of a Simplified Impression Membrane Sampling Method for the Diagnosis of Microbial Keratitis

The purpose of this study was to compare bacterial isolation rate using a corneal impression membrane (CIM) and a sharp instrument for obtaining corneal samples from patients with suspected microbial keratitis (MK). Data was retrospectively collected for all patients that had corneal samples taken for presumed MK between May 2014 and May 2020. Prior to May 2017 samples were collected by scraping the edges of the ulcer with a blade. From May 2017, samples were collected by placing a CIM (Millicell cell culture insert) against the ulcer. All corneal samples were processed using the same conventional diagnostic culture method. A total of 3099 corneal samples were included, of which 1214 (39.2%) were corneal scrapes and 1885 (60.9%) CIMs. Microorganisms were isolated from 235 (19.4%) and 1229 (65.2%) cases using a corneal scrape and CIM, respectively (p < 0.001). Of routinely described pathogenic microorganisms, there were significant increases in the isolations of S. aureus (2.4% to 11.3%) and Serratia (0.5% to 1.7%) using the CIM and no significant changes in the isolations of S. pneumoniae and P. aeruginosa. No significant differences were seen between the isolation rates of fungi or Acanthamoeba species. There was a significant increase in the isolation rates of other Streptococcal species (0.7% to 6.9%) and CNS species, specifically, S. epidermidis (2.1% to 26.2%), S. capitis (0.4% to 2.6%) and S. warneri (0.3% to 1.6%) using the CIM. The simplified CIM sampling method is an effective method for collecting corneal samples from patients with presumed MK in clinical practice.

Antimicrobial Efficacy of Contact Lens Solutions Assessed by ISO Standards

Microbial keratitis (MK) is an eye infection caused by opportunistic bacteria or fungi, which may lead to sight-threatening corneal ulcers. These microorganisms can be introduced to the eye via improper contact lens usage or hygiene, or ineffective multipurpose solutions (MPSs) to disinfect daily wear contact lenses. Thus, the patient’s choice and use of these MPSs is a known risk factor for the development of MK. It is then critical to determine the efficacy of popular MPSs against ubiquitous ocular microorganisms. Therefore, we compare the efficacy of nine major MPSs on the global market against four different microorganism species, and with four different common contact lenses. In accordance with International Standards Organization protocol 14729 and 18259, the microorganisms were inoculated into each MPS with and without contact lenses, and held for the manufacturer’s disinfection time, 24 h, and 7 days after challenge with Serratia marcescens or Fusarium spp. Plates were incubated for 2–7 days and plate counts were conducted to determine the number of surviving microorganisms. The majority of MPSs demonstrated significantly higher disinfection efficacies without contact lenses. Broadly, among the microorganisms tested, the OPTI-FREE products (Puremoist, Express, and Replenish) maintained the highest disinfection efficacies at the manufacturer’s stated disinfection time when paired with any contact lens, compared with other MPSs. These were followed closely by RevitaLens and renu Advanced. MPSs containing dual biocides polyquaternium-1 and myristamidopropyl dimethylamine possessed the highest disinfection efficacy against multiple ocular pathogens.

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.

Susceptibility of Ocular Staphylococcus aureus to Antibiotics and Multipurpose Disinfecting Solutions

Staphylococcus aureus is a frequent cause of ocular surface infections worldwide. Of these surface infections, those involving the cornea (microbial keratitis) are most sight-threatening. S. aureus can also cause conjunctivitis and contact lens-related non-infectious corneal infiltrative events (niCIE). The aim of this study was to determine the rates of resistance of S. aureus isolates to antibiotics and disinfecting solutions from these different ocular surface conditions. In total, 63 S. aureus strains from the USA and Australia were evaluated; 14 were from niCIE, 26 from conjunctivitis, and 23 from microbial keratitis (MK). The minimum inhibitory (MIC) and minimum bactericidal concentrations (MBC) of all the strains to ciprofloxacin, ceftazidime, oxacillin, gentamicin, vancomycin, chloramphenicol, azithromycin, and polymyxin B were determined. The MIC and MBC of the niCIE strains to contact lens multipurpose disinfectant solutions (MPDSs) was determined. All isolates were susceptible to vancomycin (100%). The susceptibility to other antibiotics decreased in the following order: gentamicin (98%), chloramphenicol (76%), oxacillin (74%), ciprofloxacin (46%), ceftazidime (11%), azithromycin (8%), and polymyxin B (8%). In total, 87% of all the isolates were multidrug resistant and 17% of the isolates from microbial keratitis were extensively drug resistant. The microbial keratitis strains from Australia were usually susceptible to ciprofloxacin (57% vs. 11%; p = 0.04) and oxacillin (93% vs. 11%; p = 0.02) compared to microbial keratitis isolates from the USA. Microbial keratitis isolates from the USA were less susceptible (55%) to chloramphenicol compared to conjunctivitis strains (95%; p = 0.01). Similarly, 75% of conjunctivitis strains from Australia were susceptible to chloramphenicol compared to 14% of microbial keratitis strains (p = 0.04). Most (93%) strains isolated from contact lens wearers were killed in 100% MPDS, except S. aureus 27. OPTI-FREE PureMoist was the most active MPDS against all strains with 35% of strains having an MIC ≤ 11.36%. There was a significant difference in susceptibility between OPTI-FREE PureMoist and Biotrue (p = 0.02). S. aureus non-infectious CIE strains were more susceptible to antibiotics than conjunctivitis strains and conjunctivitis strains were more susceptible than microbial keratitis strains. Microbial keratitis strains from Australia (isolated between 2006 and 2018) were more susceptible to antibiotics in comparison with microbial keratitis strains from the USA (isolated in 2004). Most of the strains were multidrug-resistant. There was variability in the susceptibility of contact lens isolates to MPDSs with one S. aureus strain, S. aureus 27, isolated from niCIE, in Australia in 1997 being highly resistant to all four MPDSs and three different types of antibiotics. Knowledge of the rates of resistance to antibiotics in different conditions and regions could help guide treatment of these diseases.