Microbial keratitis and its management at a rural centre: achieving success with limited resources

PURPOSE

Microbial keratitis is a sight-threatening condition with a higher incidence in agrarian populations. In countries with a high indigent population, due to financial and other constraints, patients prefer to seek therapy locally rather than travel to advanced centres. The aim of this study is to describe the epidemiology, clinical characteristics, and outcomes of 60 consecutive patients with microbial keratitis managed at a rural centre.

METHODS

Descriptive case series. All patients clinically diagnosed with infectious keratitis were included. Corneal scrapings were obtained and microbiological identification was done by Gram stain. Anti-microbial therapy was commenced based on smear findings and the patients were followed up till disease resolution.

RESULTS

Sixty eyes of 60 patients were diagnosed with microbial keratitis in the study period. The mean age was 47.43 ± 18.69 years. Male:female ratio was 47:53. Risk factors included ocular trauma in the majority of patients (46/60; 76.7%). Microorganisms were identified on 75.6% of smears, with fungal filaments (65.4%) being the most common. Ulcers were central in over half (32/60; 53.3%), and > 3 mm in diameter in over three-fourths (81.6%) of patients. Forty-four patients (73.3%) achieved treatment success whereas 16/60 (26.6%) required referral to our tertiary-eye care facility for management. The median time to resolution was 14 days (IQR 10-26 days).

CONCLUSION

Our series demonstrates the feasibility of microbiology-guided therapy in microbial keratitis by ophthalmologists at the secondary rural eye-care level. Two-thirds of the patients could be successfully managed at the rural centre and only severe cases needed a referral to tertiary centres.

Corneal Specialists' Confidence in Identifying Causal Organisms of Microbial Keratitis

PURPOSE

Microbial keratitis (MK) is a potentially blinding corneal disease caused by an array of microbial etiologies. However, the lack of early organism identification is a barrier to optimal care. We investigated clinician confidence in their diagnosis of organism type on initial presentation and the relationship between confidence and presenting features.

METHODS

This research presents secondary data analysis of 72 patients from the Automated Quantitative Ulcer Analysis (AQUA) study. Cornea specialists reported their confidence in organism identification. Presenting sample characteristics were recorded including patient demographics, health history, infection morphology, symptoms, and circumstances of infection. The association between confidence and presenting characteristics was investigated with 2-sample t-tests, Wilcoxon tests, and Chi-square or Fisher's exact tests.

RESULTS

Clinicians reported being "confident or very confident" in their diagnosis of the causal organism in MK infections for 39 patients (54%) and "not confident" for 33 patients (46%). Confidence was not significantly associated with patient demographics, morphologic features, or symptoms related to MK. MK cases where clinicians reported they were confident, versus not confident in their diagnosis, showed significantly smaller percentages of previous corneal disease (0% versus 15%, p = 0.017), were not seen by an outside provider first (69% versus 94%, p = 0.015), or had no prior labs drawn (8% versus 33%, p = 0.046), and a significantly larger percentage of cases wore contact lenses (54% versus 28%, p = 0.029).

CONCLUSION

In almost half of MK cases, cornea specialists reported lack of confidence in identifying the infection type. Confidence was related to ocular history and circumstances of infection but not by observable signs and symptoms or patient demographics. Tools are needed to assist clinicians with early diagnosis of MK infection type to expedite care and healing.

Concurrent determination of anti-microbial and anti-inflammatory drugs in lachrymal fluid and tissue by LC-MS/MS: A potential treatment for microbial keratitis and its PK-PD evaluation

Unforeseen surfacing of microbial keratitis (MKT) over the years has led to a requisite for promising treatment strategy involving combination of antifungal and antibacterial agents. Subsequently, symptoms associated with MKT including inflammation and watery eyes require treatment with anti-inflammatory agents. Thus, a requirement of functional clinical treatment strategy involving combination of anti-inflammatory corticosteroids (Betamethasone) with antifungal polyene (Amphotericin B, AmB) and antibacterials macrolide (Azithromycin, AZT) and aminoglycoside (Neomycin, NEO). In the ensuing pursuit, a sensitive and fast simultaneous LC-MS/MS method of four drastically different analytes in rabbit tear fluid and cornea was developed and validated as per US-FDA guidelines. The gradient LC set-up was used with C18 column and flow rate of 0.55 mL/min along with short run time of 7 min. The calibration curves showed good linearity over the concentration range of 0.07-300 ng/mL, 1.00-400 ng/mL, 3.00-600 ng/mL and 8.00-900 ng/mL for AZT, AmB, NEO and BEM respectively. The bioanalytical method requires only 10 µL of ocular sample and analytes were extracted with fast protein precipitation with acidic methanol. Finally, the developed method was validated for selectivity, linearity (r2 > 0.99), precision, accuracy, matrix effects, and stability. PK-PD indices and dosing frequency was predicted using Phoenix WinNonlin Software, based on single dose ocular pharmacokinetics and MIC values of AmB, AZT and NEO. According to the PK-PD simulation, S. aureus and E. coli required 6 and 12 instillations of AZT per 24 h, respectively whereas 12 instillation of NEO requires per 24 h for S. aureus. The result suggests that to minimize antimicrobial resistance; drug, dose and dosing schedule depend upon the pathogen as well as the strain.

A snap-shot of orthokeratology lens rinsing habits: An online survey in a major eye hospital in Shanghai

PURPOSE

A hospital-based survey to explore lens rinsing habits of orthokeratology (ortho-k) patients, including the solution used for rinsing.

METHODS

An anonymous survey, via an online questionnaire, was administered to ortho-k lens wearers or their parents when they attended Fudan University Eye and ENT Hospital for routine follow-up visits. Three major issues were investigated: basic demographics, lens rinsing solution used, and specific rinsing habits. Relationships between demographics and rinsing solution used and rinsing behaviours were explored.

RESULTS

Of the total of 541 online questionnaires delivered, 296 were completed and returned. The respondents were the person responsible for lens care, either the ortho-k users themselves, or their parents. The median age of the lens wearers was 12.0 years (range: 8-22 years), and the median period of ortho-k lens wear was 18.0 months (range: 1-109 months). The most common rinsing solutions reported were a particular brand of multidose preserved saline (28.4%), cooled boiled water (23.3%), and non-preserved multidose saline (16.2%). Overall, the main reason for choice of rinsing solution was recommendation of eye care practitioners (90.2%). The respondents with a longer lens wear history tended to use commercially available bottled water, drinking water, or cooled boiled water rather than non-preserved saline (unidose or multidose) (p ≤ 0.009) and were more likely to use the rinsing solution to soak their lenses (p = 0.009). Lens wearers who rinsed the lenses themselves tended to use tap water compared to those whose lenses were handled by parents (p = 0.040).

CONCLUSION

Inappropriate choice and usage of rinsing solution appeared to be a common issue among ortho-k lens wearers in Shanghai, China. The problem was more pronounced in long-term wearers and in those who performed rinsing themselves.

Collagen cross-linking as monotherapy in experimentally induced corneal abscess in rabbits

BACKGROUND AND PURPOSE

Collagen cross-linking (CXL) has evolved as an essential therapeutic approach for corneal infections, allowing for rapidly eliminating the infecting microorganism while reducing inflammation. This study aims to evaluate the efficacy of CXL as a monotherapy for managing infectious keratitis caused by Fusarium solani and Pseudomonas aeruginosa.

MATERIALS AND METHODS

Forty-eight white New Zealand rabbits weighing approximately 1.5-2 KG were included. The cornea of one eye of each rabbit was inoculated with either Fusarium solani or Pseudomonas aeruginosa. Group A served as a control and was subdivided into two subgroups, A1 and A2; each subgroup consisted of 8 eyes and was injected with either Fusarium solani or Pseudomonas aeruginosa, respectively. Group B (16 eyes) was inoculated with Fusarium solani, while group C (16 eyes) were inoculated with Pseudomonas aeruginosa. All animals in Group B and C received CXL treatment one week after inoculation of the organisms and after corneal abscess formation was confirmed. At the same time, animals in Group A were left untreated.

RESULTS

There was a statistically significant reduction in the number of colony-forming units (CFU) in Group B following CXL. No growth existed in any samples at the end of the 4th week. There was a statistically significant difference in the number of CFU between group B and the control group (p < 0.001). In group C, there was a statistically significant reduction in the CFU at the end of the first week after CXL. However, there was regrowth in all samples afterward. All 16 models in Group C showed uncountable and extensive growth during the subsequent follow-ups. There was no statistically significant difference between the number of CFU in Group C and the control group. Histopathology showed lesser corneal melting in CXL-treated Pseudomonas aeruginosa.

CONCLUSIONS

Collagen cross-linking is promising monotherapy and alternative treatment in managing infective keratitis caused by Fusarium solani but is less effective in Pseudomonas aeruginosa as monotherapy.

Atypical microbial keratitis

Atypical microbial keratitis refers to corneal infections caused by micro-organisms not commonly encountered in clinical practice. Unlike infections caused by common bacteria, cases of atypical microbial keratitis are often associated with worse clinical outcomes and visual prognosis. This is due to the challenges in the identification of causative organisms with standard diagnostic techniques, resulting in delays in the initiation of appropriate therapies. Furthermore, due to the comparatively lower incidence of atypical microbial keratitis, there is limited literature on effective management strategies for some of these difficult to manage corneal infections. This review highlights the current management and available evidence of atypical microbial keratitis, focusing on atypical mycobacteria keratitis, nocardia keratitis, achromobacter keratitis, and pythium keratitis. It will also describe the management of two uncommonly encountered conditions, infectious crystalline keratopathy and post-refractive infectious keratitis. This review can be used as a guide for clinicians managing patients with such challenging corneal infections.

A study on childhood microbial keratitis in South India

Purpose

The aim of this study was to determine the predisposing risk factors, clinical characteristics, microbiological profile, and visual and functional treatment outcome of microbial keratitis including viral keratitis in children.

Methods

A prospective study was carried out in a tertiary care institute over a period of 18 months on 73 pediatric patients. Data collected was analyzed for demographics of the patient population, causative organisms, and management outcome in terms of visual and functional outcome.

Results

Patients in the age group from 1 month to 16 years were included, with a mean age of 10.81 years. Trauma was the commonest risk factor (40.9%), with unidentified foreign body fall being the most common (32.3%). No predisposing factors were identified in 50% of cases. Also, 36.8% of eyes were culture positive, with bacterial isolates in 17.9% and fungus in 82.1%. Moreover, 7.1% eyes were culture positive for Streptococcus pneumoniae and Pseudomonas aeruginosa each. Fusarium species (67.8%) was the commonest fungal pathogen, followed by Aspergillus species (10.7%). Also, 11.8% were clinically diagnosed as viral keratitis. No growth was found in 63.2% of patients. Treatment with broad-spectrum antibiotics/antifungals was administered in all cases. At the final follow-up, 87.8% achieved a best corrected visual acuity (BCVA) of 6/12 or better. Therapeutic penetrating keratoplasty (TPK) was required by 2.6% of eyes.

Conclusion

Trauma was the major cause for pediatric keratitis. Majority of the eyes responded well to medical treatment, with only two eyes needing TPK. Early diagnosis and prompt management helped majority of the eyes to achieve a good visual acuity after the resolution of keratitis.

Enterobacter Cloacae keratitis after corneal cross-linking for keratoconus: A case report

PURPOSE

To report a case of Enterobacter cloacae (E. cloacae) keratitis in a patient who underwent corneal crosslinking (CXL) for progressive keratoconus.

OBSERVATIONS

A 19-year-old female underwent CXL for keratoconus in her left eye. The patient neglected her post-procedure medications and missed the follow-up visit. Subsequently, she presented on day-10 post CXL with redness and pain in the treated eye. Clinical examination revealed a ring-shape infiltrate measuring 7.8 mm in diameter. Culture indicated the presence of E. cloacae. Treatment with gentamicin failed after the emergence of resistance. The patient was successfully treated with amikacin and moxifloxacin over several weeks.

CONCLUSIONS

Judicious antibiotic selection is crucial to limit the emergence of resistance in multidrug-resistant (MDR) pathogens. All patients need to be educated about their role in the management plan.

Challenges in management of microbial keratitis during COVID-19 pandemic related lockdown: a comparative analysis with pre pandemic data

Purpose

To study the challenges of managing microbial keratitis(MK) during the COVID19 pandemic related lockdown and assess the outcomes of treatment at a tertiary cornea service.

Methods

Retrospective, non comparative study of electronic medical records of MK presenting to a network of four tertiary care cornea services. The medical history, presenting clinical features, microbiology work up and treatment outcomes were analyzed. The primary outcome measure was final outcome at last follow up. Secondary outcomes measures were non-compliance to treatment due to travel restrictions, therapeutic PKP not done due non availability of corneal tissues. Results- MK was noted in 330 eyes of 330 patients between April and May 2020. Of these 237(71.8%) were males. Median age was 45 years(IQR, 33-56). Low socioeconomic status noted in 102(30.9%). Patients travelling beyond the district from where the hospital was located comprised of 64.9%(n=214). At a median follow up of 32 days(IQR, 9-54), 118(35.8%) patients had resolved, with medical management, 73(22.1%) patients were under active treatment, 139(42.1%) were lost to follow up. Sixty-six patients(20%) were non-compliant to treatment of which 59 could not follow appointment schedule due to travel restrictions. Therapeutic PKP (TPK) was planned in 48/128 (37.5%) patients, but was performed in only 34/48 (70.8%) due to non-availability of donor corneas.

Conclusions

Abnormal social circumstances due to the COVID pandemic and the ensuing impediments to travel for access to health care affected compliance to treatment of ocular emergencies such as microbial keratitis.

Microbial Keratitis following Self-Retained Cryopreserved Amniotic Membrane

The aim of this study was to report a severe case of mixed fungal and bacterial microbial keratitis following implantation of a self-retained cryopreserved amniotic membrane, PROKERA® SLIM (Bio-Tissue, Inc) in a patient with history of neurotrophic ulcer secondary to herpetic epithelial keratitis. Despite maximally tolerated topical and systemic therapy, the patient's eye continued to deteriorate and eventually required evisceration. PROKERA implantation might be associated with severe recalcitrant microbial keratitis. Caution is urged when considering implantation especially in monocular patients.

Preclinical confirmation of UVC efficacy in treating infectious keratitis

PURPOSE

Preclinical evaluation of the therapeutic potential of antimicrobial 265 nm UVC for infectious keratitis.

METHODS

Four experiments explored UVC: 1) impact on bacterial and fungal lawns on agar, in individual or mixed culture, 2) bacterial inactivation dose in an in vitro deep corneal infection model, 3) dose validation in an ex vivo porcine keratitis model and 4) efficacy in a masked, randomised, controlled murine keratitis trial using bioluminescent Pseudomonas aeruginosa.

RESULTS

Minimum effective UVC exposures ranged between 2 s and 5 s for lawn bacteria and fungi in individual or mixed culture. Significant P. aeruginosa growth inhibition in the in vitro infection model was achieved with 15 s UVC, that resulted in a >3.5 log10 reduction of bacteria in a subsequent ex vivo keratitis model (p < 0.05). Bioluminescence fell below baseline levels in all treated animals, within 8 h of treatment (p < 0.05), in the in vivo study. Re-epithelialisation with corneal clarity occurred within 24 h in 75% of UVC-treated cases, with no relapse at 48 h. On plating, bacteria were recovered only from untreated controls.

CONCLUSIONS

UVC inhibited all tested bacteria and fungi, including mixed culture and strains linked to antibiotic resistance, in vitro, with exposures of ≤ 5 s. In vitro and ex vivo testing confirmed therapeutic potential of 15 s UVC. In vivo, 15 s UVC administered in two doses, 4 h apart, proved effective in treating murine bacterial keratitis.

Clinical profile of keratitis treated within 3 months of acute COVID-19 illness at a tertiary care eye centre

Purpose

To report the spectrum of keratitis treated within 3 months of acute COVID-19 infection.

Methods

Retrospective, descriptive case series study of 19 eyes of 16 patients who presented at tertiary eye care centre in Southern India.

Results

Median age of the patients was 43(IQR 35–55.5) years. Majority (15/16, 93.75%) were males. Unilateral affliction was predominant (13/16, 81.25% patients). Nine had a history of hospitalization, five had received oxygen supplementation and five had been treated with steroids during COVID-19 illness. The median duration between COVID-19 diagnosis and the ocular symptoms in the eye was 29 (IQR 22–57) days. Microbiological diagnosis consisted of microsporidia in nine eyes of seven patients, fungus in six patients, Pythium in one patient, and herpes zoster ophthalmicus in one patient. One patient had neurotrophic keratitis. Therapeutic penetrating keratoplasty was performed in five patients, glue application in two patients and three were managed with tarsorrhaphy with/without amniotic membrane grafting or tenonplasty. There was medical and surgical cure in all patients.

Conclusions

Microsporidia was the commonest cause of keratitis, followed by fungal infection. Majority of the microsporidia infections were keratoconjunctivitis. The fungal isolates identified were Aspergillus and Mucor species. All patients responded to conventional management guidelines with favourable outcomes.

Bacterial keratitis: identifying the areas of clinical uncertainty

Bacterial keratitis is a common corneal infection that is treated with topical antimicrobials. By the time of presentation there may already be severe visual loss from corneal ulceration and opacity, which may persist despite treatment. There are significant differences in the associated risk factors and the bacterial isolates between high income and low- or middle-income countries, so that general management guidelines may not be appropriate. Although the diagnosis of bacterial keratitis may seem intuitive there are multiple uncertainties about the criteria that are used, which impacts the interpretation of investigations and recruitment to clinical studies. Importantly, the concept that bacterial keratitis can only be confirmed by culture ignores the approximately 50% of cases clinically consistent with bacterial keratitis in which investigations are negative. The aetiology of these culture-negative cases is unknown. Currently, the estimation of bacterial susceptibility to antimicrobials is based on data from systemic administration and achievable serum or tissue concentrations, rather than relevant corneal concentrations and biological activity in the cornea. The provision to the clinician of minimum inhibitory concentrations of the antimicrobials for the isolated bacteria would be an important step forward. An increase in the prevalence of antimicrobial resistance is a concern, but the effect this has on disease outcomes is yet unclear. Virulence factors are not routinely assessed although they may affect the pathogenicity of bacteria within species and affect outcomes. New technologies have been developed to detect and kill bacteria, and their application to bacterial keratitis is discussed. In this review we present the multiple areas of clinical uncertainty that hamper research and the clinical management of bacterial keratitis, and we address some of the assumptions and dogma that have become established in the literature.

Commercial soft contact lenses engineered with zwitterionic silver nanoparticles for effectively treating microbial keratitis

The introduction of various drugs onto commercial soft contact lenses (CLs) has emerged as a potentially effective strategy for treating microbial keratitis (MK) because drug-loaded CLs can maintain a controlled drug concentration which leaded to enhanced drug bioavailability and reduced side effects in ocular tissues. In this study, silver nanoparticles modified with zwitterionic poly (carboxybetaine-co-dopamine methacrylamide) copolymer (PCBDA@AgNPs) as novel anti-infective therapeutics were prepared and firmly immobilized onto soft CLs through mussel-inspired surface chemistry. The obtained PCBDA@AgNPs coated CL (PCBDA@AgNPs-CL) remained the excellent transparency of commercial CLs and exhibited strong and broad-spectrum antimicrobial activities. We systematically explored the mechanism and found that the functional CLs can effectively inhibit the growth of microbial biofilms via a synergic "resist-kill-remove" strategy due to the zwitterionic surface and sustained release of silver ions. Significantly, in vitro cell cytotoxicity and in vivo subcutaneous implantation experiments proved the significant biosafety of PCBDA@AgNPs-CL. Furthermore, PCBDA@AgNPs-CL was successfully employed for the in vivo treatment of MK rabbit models, demonstrating excellent abilities to eradicate microbe-induced ocular infections and to prevent the destruction and irreversible structural alterations of corneal tissues. Collectively, PCBDA@AgNPs-CL is therefore a highly promising therapeutic device to significantly boost the efficacy for MK treatment.

Efficacy, predictability and safety of long-term orthokeratology: An 18-year follow-up study

PURPOSE

To determine the efficacy, predictability and safety of long-term orthokeratology in children and adults.

METHODS

Case histories of 300 orthokeratology patients (596 eyes; 34.3% children; 65.7% adults) were reviewed to collect information on demographics, corneal and refractive parameters, visual acuity, residual refraction and adverse effects. Predictability was defined as the percentage of eyes with absolute values of spherical equivalent refraction ≤ 0.5 D of emmetropia, and efficacy as the ratio of post-orthokeratology uncorrected and pre-orthokeratology corrected distance visual acuity.

RESULTS

Median duration of treatment was 37 and 28.5 months in children and adults, respectively (p = 0.022). During the first year, 17.2% of children and 33% of adults ceased lens wear (p < 0.001). For children and adults with a successful ortho-k treatment of at least one year of duration, 88.7% and 95.9% of eyes had a predictable refractive outcome, and efficacy was 0.98 and 1.01, respectively. A larger percentage of children (65.7%) were free of complications than of adults (55.4%) (p = 0.015). One event of microbial keratitis occurred in adults (6.8 cases per 10,000 patient-years) and none in children. Corneal staining was the most frequent complication, with a higher incidence in adults (p = 0.007) and in higher myopia (p < 0.001), higher anterior corneal eccentricity (p = 0.019) and smaller anterior horizontal radius (p = 0.027).

CONCLUSION

Orthokeratology is a safe and predictable long-term procedure in children and adults, with a low incidence of serious adverse effects. Corneal staining episodes are relatively frequent throughout the course of the treatment, thus highlighting the relevance of education of experienced users.

Late-onset granular intra-amniotic infection following amniotic membrane transplantation

Background

The amniotic membrane (AM) is used in ocular surface reconstruction and is effective at promoting epithelialization and preventing corneal perforation in cases of acute microbial keratitis. Here, we report a case of isolated AM infection after AM transplantation for a persistent epithelial defect following tectonic penetrating keratoplasty.

Case presentation

A 47-year-old man with poorly controlled type 2 diabetes mellitus presented to the emergency department with a referral for perforated microbial keratitis. After ophthalmic examination, corneal scraping was performed, and corneal gluing was attempted and failed. Hence, the patient underwent tectonic penetrating keratoplasty. After keratoplasty, the patient developed a persistent epithelial defect that required AM transplantation as an overlay. Thirty days post-AM transplant, the patient presented with signs and symptoms resembling granular microbial infection of the cornea. After two days, the granular findings began dislodging from the corneal surface and were sent for culture, sensitivity, and histopathological identification. Histological analysis of the granular material indicated it to be a small piece of AM stroma infiltrated with mixed-type inflammatory cells. Corneal scraping cultures indicated Streptococcus mitis and Streptococcus oralis.

Conclusion

The infiltrate was localized to the basement membrane of the AM as, despite the anti-inflammatory effects of AM, it can also act as a barrier against polymorphonuclear leukocyte infiltration from the tear film and microbial invasion into the cornea.

Foundational concepts in the biology of bacterial keratitis

Bacterial infections of the cornea, or bacterial keratitis (BK), are notorious for causing rapidly fulminant disease and permanent vision loss, even among treated patients. In the last sixty years, dramatic upward trajectories in the frequency of BK have been observed internationally, driven in large part by the commercialization of hydrogel contact lenses in the late 1960s. Despite this worsening burden of disease, current evidence-based therapies for BK - including broad-spectrum topical antibiotics and, if indicated, topical corticosteroids - fail to salvage vision in a substantial proportion of affected patients. Amid growing concerns of rapidly diminishing antibiotic utility, there has been renewed interest in urgently needed novel treatments that may improve clinical outcomes on an individual and public health level. Bridging the translational gap in the care of BK requires the identification of new therapeutic targets and rational treatment design, but neither of these aims can be achieved without understanding the complex biological processes that determine how bacterial corneal infections arise, progress, and resolve. In this chapter, we synthesize the current wealth of human and animal experimental data that now inform our understanding of basic BK pathophysiology, in context with modern concepts in ocular immunology and microbiology. By identifying the key molecular determinants of clinical disease, we explore how novel treatments can be developed and translated into routine patient care.

Cationic Polyelectrolyte Nanocapsules of Moxifloxacin for Microbial Keratitis Therapy: Development, Characterization, and Pharmacodynamic Study

Microbial keratitis (MK) is a vision-threatening disease and the fourth leading cause of blindness worldwide. In this work, we aim to develop moxifloxacin (MXN)-loaded chitosan-based cationic mucoadhesive polyelectrolyte nanocapsules (PENs) for the effective treatment of MK. PENs were formulated by polyelectrolyte complex coacervation method and characterized for their particle size, surface charge, morphology, mucoadhesive property, in-vitro and ex-vivo release, ocular tolerance, and antimicrobial efficacy studies. The pharmacodynamic study was conducted on rabbit eye model of induced keratitis and it is compared with marketed formulation (MF). Developed PENs showed the size range from 230.7 ± 0.64 to 249.0 ± 0.49 nm and positive surface charge, spherical shape along with appropriate physico-chemical parameters. Both in-vitro and ex-vivo examination concludes that PENs having more efficiency in sustained release of MXN compared to MF. Ocular irritation studies demonstrated that no corneal damage or ocular irritation. The in-vivo study proved that the anti-bacterial efficacy of PENs was improved when compared with MF. These results suggested that PENs are a feasible choice for MK therapy because of their ability to enhance ocular retention of loaded MXN through interaction with the corneal surface of the mucous membrane.

Risk factors, clinical features and outcomes of Neisseria keratitis

OBJECTIVE

To describe the clinical features, risk factors and outcomes of Neisseria keratitis.

METHODS

This is a retrospective observational study wherein medical records of cases with microbiologically proven Neisseria keratitis were reviewed. Data pertaining to the underlying predisposing factors, clinical characteristics of the corneal ulcer, antibiotic susceptibility of the Neisseria species isolate from the corneal scraping, the treatment given, and outcomes were collected and analyzed.

RESULTS

Medical records of 60 patients (60 eyes) with Neisseria keratitis were reviewed. Among the causes of poor ocular surface as predisposing factor, vernal keratoconjunctivitis (n = 6 eyes), along with use of topical corticosteroids (n = 18 eyes) was the most common. The ulcer was characterized by a central infiltrate (31/60, 51.7%) involving up to the mid-stroma (43/60, 71.7%). Of the forty-four (73.3%) eyes with pure Neisseria keratitis, 31 eyes (72.1%) resolved with medical therapy alone while five eyes (11.6%) underwent therapeutic penetrating keratoplasty and in two (4.6%) eyes evisceration was performed. The other 5/44 (11.6%) patients were lost to follow-up. Resolution with medical therapy was found to be similar in cases with pure infection and mixed infection (p = 0.58).

CONCLUSIONS

Neisseria keratitis most commonly causes a mild form of keratitis and is often associated with the poor ocular surface or prior steroid use. In most cases medical therapy is sufficient for complete resolution of the keratitis.

The role of nitric oxide in ocular surface physiology and pathophysiology

Nitric oxide (NO) has a wide array of biological functions including the regulation of vascular tone, neurotransmission, immunomodulation, stimulation of proinflammatory cytokine expression and antimicrobial action. These functions may depend on the type of isoform that is responsible for the synthesis of NO. NO is found in various ocular tissues playing a pivotal role in physiological mechanisms, namely regulating vascular tone in the uvea, retinal blood circulation, aqueous humor dynamics, neurotransmission and phototransduction in retinal layers. Unregulated production of NO in ocular tissues may result in production of toxic superoxide free radicals that participate in ocular diseases such as endotoxin-induced uveitis, ischemic proliferative retinopathy and neurotoxicity of optic nerve head in glaucoma. However, the role of NO on the ocular surface in mediating physiology and pathophysiological processes is not fully understood. Moreover, methods used to measure levels of NO in the biological samples of the ocular surface are not well established due to its rapid oxidation. The purpose of this review is to highlight the role of NO in the physiology and pathophysiology of ocular surface and propose suitable techniques to measure NO levels in ocular surface tissues and tears. This will improve the understanding of NO's role in ocular surface biology and the development of new NO-based therapies to treat various ocular surface diseases. Further, this review summarizes the biochemistry underpinning NO's antimicrobial action.

Evaluation of full-length nanopore 16S sequencing for detection of pathogens in microbial keratitis

BACKGROUND

Microbial keratitis is a leading cause of preventable blindness worldwide. Conventional sampling and culture techniques are time-consuming, with over 40% of cases being culture-negative. Nanopore sequencing technology is portable and capable of generating long sequencing reads in real-time. The aim of this study is to evaluate the potential of nanopore sequencing directly from clinical samples for the diagnosis of bacterial microbial keratitis.

METHODS

Using full-length 16S rRNA amplicon sequences from a defined mock microbial community, we evaluated and benchmarked our bioinformatics analysis pipeline for taxonomic assignment on three different 16S rRNA databases (NCBI 16S RefSeq, RDP and SILVA) with clustering at 97%, 99% and 100% similarities. Next, we optimised the sample collection using an ex vivo porcine model of microbial keratitis to compare DNA recovery rates of 12 different collection methods: 21-gauge needle, PTFE membrane (4 mm and 6 mm), Isohelix™ SK-2S, Sugi® Eyespear, Cotton, Rayon, Dryswab™, Hydraflock®, Albumin-coated, Purflock®, Purfoam and Polyester swabs. As a proof-of-concept study, we then used the sampling technique that provided the highest DNA recovery, along with the optimised bioinformatics pipeline, to prospectively collected samples from patients with suspected microbial keratitis. The resulting nanopore sequencing results were then compared to standard microbiology culture methods.

RESULTS

We found that applying alignment filtering to nanopore sequencing reads and aligning to the NCBI 16S RefSeq database at 100% similarity provided the most accurate bacterial taxa assignment. DNA concentration recovery rates differed significantly between the collection methods (p < 0.001), with the Sugi® Eyespear swab providing the highest mean rank of DNA concentration. Then, applying the optimised collection method and bioinformatics pipeline directly to samples from two patients with suspected microbial keratitis, sequencing results from Patient A were in agreement with culture results, whilst Patient B, with negative culture results and previous antibiotic use, showed agreement between nanopore and Illumina Miseq sequencing results.

CONCLUSION

We have optimised collection methods and demonstrated a novel workflow for identification of bacterial microbial keratitis using full-length 16S nanopore sequencing.

Contact lens wear and care in Spain during the COVID-19 pandemic

AIM

To establish contact lens wear and care practices during the COVID-19 pandemic in Spain.

METHOD

A 58-item anonymous online survey was distributed during the period 30th April to 10th May via Qualtrics. The survey explored: a) demographic characteristics (age, sex, general health and where they were living during lockdown), b) changes in their contact lens use during lockdown, c) hygiene and contact lens compliance and d) concerns associated with contact lens wear and ways to support wearers during the pandemic.

RESULTS

Two hundred and sixty responses were analysed (38.8 ± 11.4 years old, 75% female). Three-quarters of participants reported that they were self-isolating or rigorously following social distancing advice. Sixty-seven percent of participants reported using their contact lenses less during the pandemic. Respondents were found to be compliant with handwashing prior to inserting and removing contact lenses (in both cases 97% doing this 'most times' or 'every time'). However, only 44 % complied with the '20 s rule' and 48 % used a shared towel to dry their hands. A higher proportion of hydrogen peroxide users replaced the lens case monthly compared to multi-purpose users (64% vs.49%; p < 0.001). Twenty-four percent admitted wearing lenses whilst showering and 16% did not consider ceasing lens wear if feeling unwell with flu/cold symptoms.

CONCLUSION

Eye care practitioners should continue to educate contact lens wearers to ensure safe contact lens wear to minimise the chance of developing contact lens related complications during the pandemic. Modifiable factors that need particular attention in Spain include: handwashing for at least 20s before lens handling, drying hands with single use paper towels, including a rub-and-rinse step for reusable lenses, lens case cleaning and renewal, avoidance of water exposure and when to cease lens wear during the pandemic.

Recent progress and strategies to develop antimicrobial contact lenses and lens cases for different types of microbial keratitis

Although contact lenses are widely used for vision correction, they are also the primary cause of a number of ocular diseases such as microbial keratitis (MK), etc. and inflammatory events such as infiltrative keratitis (IK), contact lens acute red eye (CLARE), contact lens-induced peripheral ulcer (CLPU), etc. These diseases and infiltrative events often result from microbial contamination of lens care solutions and lens cases that can be exacerbated by unsanitary lens care and extended lens wear. The treatment of microbial biofilms (MBs) on lens cases and contact lenses are complicated and challenging due to their resistance to conventional antimicrobial lens care solutions. More importantly, MK caused by MBs can lead to acute visual damage or even vision impairment. Therefore, the development of lens cases, lens care solutions, and contact lenses with effective antimicrobial performance against MK will contribute to the safe use of contact lenses. This review article summarizes and discusses different chemical approaches for the development of antimicrobial contact lenses and lens cases employing passive surface modifications, antimicrobial peptides, free-radical fabricating agents, quorum sensing quenchers, antibiotics, antifungal drugs and various metals and coatings with antimicrobial nanomaterials. The benefits and shortcomings of these approaches are assessed, and alternative solutions for future developments are discussed.

Distribution of Microbial Keratitis After Penetrating Keratoplasty According to Early and Late Postoperative Periods

Objectives:

The aim of this study was to investigate the distribution of microbial agents in the early and late postoperative periods in patients with microbial keratitis (MK) after penetrating keratoplasty (PK).

Materials and Methods:

The records of 36 patients who were clinically diagnosed as having MK after PK were retrospectively reviewed. Culture results were obtained from microbiology records and the organisms that were produced were noted. A case was deemed as viral keratitis based on the clinical appearance, negative cultures, and response to antiviral treatment. Keratitis development times were evaluated in 2 categories: early (within the first year) and late (after year 1) postoperative period. Mann-Whitney U and Kruskal-Wallis tests were used to compare numerical variables that did not show normal distribution and chi-square test was used to compare categorical variables.

Results:

The majority of MK cases were of bacterial origin (55.5%, n=20), followed by viral (41.7%, n=15) and fungal (2.8%, n=1). Of the 15 cases of early postoperative MK, 10 were bacterial, 4 were viral, and 1 was fungal; however, among cases of late postoperative MK, 10 were bacterial and 11 were viral. The majority (65%) of early and late bacterial infections were caused by gram-positive strains (most commonly staphylococci). Gram-positive bacteria caused keratitis significantly earlier than gram-negative bacteria (p=0.037). Viral and gram-negative bacterial MK was more frequent in the late postoperative period, but the difference was not statistically significant.

Conclusion:

In our study, bacterial keratitis was more common in post-keratoplasty MK than viral and fungal keratitis. Gram-positive bacteria were the most common causative agents. The increased incidence of gram-negative bacterial agents and viral keratitis in the late postoperative period can be explained by long-term topical steroid use.

Soft contact lens wearers' compliance during the COVID-19 pandemic

Aim

Contact lens wearers need to maintain optimal hygiene practices during the COVID-19 pandemic to minimise contact-lens complications including microbial keratitis and corneal infiltrative events. This online survey (UK and Ireland) explored contact lens wearers’ compliance behaviours, attitudes and concerns during the pandemic.

Method

The 60-item anonymous online survey was distributed during a 1-month period via Qualtrics (starting on 14/04/20). The survey captured: a) demographic information, b) type of lenses worn and compliance with lens wear and care procedures, c) adherence to recommendations and d) concerns associated with contact lens wear during the pandemic.

Results

Two hundred and forty seven responses were received (34.3 ± 11.7 years old, 79% female). Seventy nine percent of participants reported that they were self-isolating or rigorously following social distance advice. Fifty-six percent of participants reported using their lenses less during the pandemic. Eighty-seven percent of respondents reported following the recommended 20-second rule most times/every time and 96% used soap and water during handwashing. Eleven percent of respondents admitted not following recommendations regarding disposal of lenses and 18% would not consider ceasing lens wear if unwell (with flu/cold) during the pandemic.

Conclusion

Respondents reported wearing their contact lenses less than usual. Good compliance with handwashing was observed but soft reusable lens wearers showed a statistically significant lower compliance with lens wear and care compared to daily disposable lens wearers (p=<0.001).

Antibiotic eye drops prescription patterns by orthokeratology practitioners in China and the development of antibiotic usage guidelines

PURPOSE

To investigate antibiotic eye drops prescribing patterns of contact lens practitioners in Mainland China for orthokeratology (ortho-k) patients and to develop guidelines for their use.

METHODS

A questionnaire on their antibiotic prescribing habits was administered to eye care practitioners (ECP) involved in ortho-k lens fitting nationwide via an official online account. Multiple logistic regression models were used to assess the relationships between prescribing habits and demographics.

RESULTS

A total of 555 ECP completed the survey, of whom 50.5 % were optometrists (non-medical degree). About 30 % of the respondents routinely prescribed antibiotic eye drops for prophylactic use before and/or after commencement of ortho-k treatment. Forty one percent of the respondents dispensed antibiotics to patients for emergency use without giving written instructions, 48.5 % used antibiotic eye drops to wet fluorescein strips during ortho-k lens fitting, and 44.9 % considered treating corneal infiltrate(s) with antibiotics to be appropriate. A set of guidelines, including when to use antibiotic eye drops during ortho-k lens treatment and their proper use, stratified by different corneal conditions, was developed.

CONCLUSIONS

Inappropriate use of antibiotic eye drops appeared to be common among ortho-k practitioners in Mainland China. Taking into account deficiencies and errors identified from the survey, a set of guidelines based on best practice was developed and can serve to provide advice for proper use of antibiotics in ortho-k practice.

Overnight orthokeratology

Overnight orthokeratology lenses are approved in countries all over the world for the temporary reduction in myopia, and recently, one lens design has received regulatory approval for myopia control in Europe. The modern orthokeratology lens has a substantial history from its origins of attempting to flatten the corneal curvature with a spherical rigid contact lens to sophisticated gas permeable lenses, designed to reshape the cornea. These lenses are predominantly prescribed for children to slow myopia progression and limit axial elongation of the eye. This article reviews the peer-reviewed literature on the efficacy of orthokeratology for myopia control, sustainability after treatment is discontinued, and the safety concerns of overnight contact lens wear. Future avenues of research are discussed.

pHEMA@AGMNA-1: A novel material for the development of antibacterial contact lens

The Metal Organic Framework (MOF) of formula {[Ag₆(μ₃-HMNA)₄(μ₃-MNA)₂]^2-·[(Et₃NH)⁺]₂·(DMSO)₂·(H₂O)} (AGMNA), a known efficient antimicrobial compound which contains the anti-metabolite, 2-thio-nicotinic acid (H₂MNA), was incorporated in polymer hydrogels using, hydroxyethyl-methacrylate (HEMA). The material pHEMA@AGMNA-1 was characterized by X-ray fluorescence (XRF) spectroscopy, X-ray powder diffraction analysis (XRPD), Scanning Electron Microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX), Thermogravimetric Differential Thermal Analysis (TG-DTA), Differential Scanning Calorimetry (DTG/DSC), attenuated total reflection spectroscopy (FT-IR-ATR) and Ultrasonic Imaging. The antimicrobial capacity of pHEMA@AGMNA-1 was evaluated against the Gram negative bacterial strain Pseudomonas aeruginosa and the Gram positive ones of the genus of Staphylococcus epidermidis and Staphylococcus aureus, which are the etiology of the microbial keratitis. The % bacterial viability of P. aeruginosa, S. epidermidis and S. aureus upon their incubation with pHEMA@AGMNA-1 discs is significantly low (0.4 ± 0.1%, 1.5 ± 0.4% and 7.7 ± 0.5% respectively). The inhibition zones (IZ) caused by pHEMA@AGMNA-1 discs against P. aeruginosa, S. epidermidis and S. aureus are 14.0 ± 1.1, 11.3 ± 1.3 and 11.8 ± 1.8 mm respectively. Furthermore, pHEMA@AGMNA-1 exhibits low toxicity. Thus, pHEMA@AGMNA-1 might be an efficient candidate for the development of antimicrobial active contact lenses.

Outcome of therapeutic deep anterior lamellar keratoplasty in advanced Acanthamoeba keratitis

Purpose

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

Methods

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

Results

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

Conclusion

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

Clinical metagenomics for infectious corneal ulcers: Rags to riches?

The emergence of clinical metagenomics as an unbiased, hypothesis-free approach to diagnostic testing is set to fundamentally alter the way infectious diseases are detected. Long envisioned as the solution to the limitations of culture-based conventional microbiology, next generation sequencing methods will soon mature, and our attention will inevitably turn to how they can be applied to areas of medicine which need it most urgently. In ophthalmology, the demand for this technology is particularly pressing for the care of infectious corneal ulcers, where current diagnostic tests may fail to identify a causative organism in over half of cases. However, the optimism found in the budding discourse surrounding clinical metagenomics belies the reality that clinicians and scientists will soon be inundated by oppressive volumes of sequencing data, much of which will be foreign and unfamiliar. Therefore, our success in translating clinical metagenomics is likely to hinge on how we make sense of these data, and understanding its implications for the interpretation and implementation of sequencing into routine clinical care. In this consortium-led review, we provide an outline of these data-related issues and how they may be used to inform technical workflows, with the hope that we may edge closer to realizing the potential of clinical metagenomics for this important unmet need.

Epidemiology of Microbial Keratitis in Uganda: A Cohort Study

Purpose

To describe the epidemiology of Microbial Keratitis (MK) in Uganda.

Methods

We prospectively recruited patients presenting with MK at two main eye units in Southern Uganda between December 2016 and March 2018. We collected information on clinical history and presentation, microbiology and 3-month outcomes. Poor vision was defined as vision < 6/60).

Results

313 individuals were enrolled. Median age was 47 years (range 18–96) and 174 (56%) were male. Median presentation time was 17 days from onset (IQR 8–32). Trauma was reported by 29% and use of Traditional Eye Medicine by 60%. Majority presented with severe infections (median infiltrate size 5.2 mm); 47% were blind in the affected eye (vision < 3/60). Microbiology was available from 270 cases: 62% were fungal, 7% mixed (bacterial and fungal), 7% bacterial and 24% no organism detected. At 3 months, 30% of the participants were blind in the affected eye, while 9% had lost their eye from the infection. Delayed presentation (overall p = .007) and prior use of Traditional Eye Medicine (aOR 1.58 [95% CI 1.04–2.42], p = .033) were responsible for poor presentation. Predictors of poor vision at 3 months were: baseline vision (aOR 2.98 [95%CI 2.12–4.19], p < .0001), infiltrate size (aOR 1.19 [95%CI 1.03–1.36], p < .020) and perforation at presentation (aOR 9.93 [95% CI 3.70–26.6], p < .0001).

Conclusion

The most important outcome predictor was the state of the eye at presentation, facilitated by prior use of Traditional Eye Medicine and delayed presentation. In order to improve outcomes, we need effective early interventions.

Childhood and lifetime risk comparison of myopia control with contact lenses

PURPOSE

The relative risks of ocular pathology with increasing myopia have been described; the absolute lifetime risk of vision impairment from myopia is yet to be compared to the childhood and lifetime risks of contact lens wear for myopia control.

METHODS

Using peer-reviewed data, the absolute risks of microbial keratitis (MK) in daily disposable soft, reusable soft and orthokeratology contact lens (CL) wear were calculated over both a childhood (age 8-18) and a lifetime (age 8-65) of CL wear. This was compared to the previously published cumulative risk of vision impairment by age 75 based on increasing myopia and axial length. Data were converted utilizing the Council of International Organizations of Medical Sciences (CIOMS) classification system for frequency of adverse events, with 95 % confidence intervals included.

RESULTS

The lifetime risk of vision impairment in axial lengths over 26 mm and more than 6D of myopia is greater than the lifetime risk of MK in any CL modality, except for adult SCL extended wear. If axial length is below 26 mm and myopia lower than 3D, a lifetime of CL wear is more risky in comparison, except in the case of daily disposable wear. Ten years of childhood CL wear of any modality presents lower likelihood of MK than any comparable risk of vision impairment.

CONCLUSION

The comparative lifetime risks of contact lens wear commenced at age 8 for myopia control are less than the lifetime risks of vision impairment with myopia more than 6D or axial length more than 26 mm. When only childhood CL wear is considered, the risk comparison is clearly skewed towards the positive impact of CL wear, especially in daily disposable wear. Clinicians should be confident to proactively recommend myopia control CL wear to younger children, as both the safety profile and potential preventative ocular health benefits are evident.

Atypical herpes simplex keratitis: frequency, clinical presentations and treatment results

AIMS

To determine herpes simplex virus (HSV) DNA positivity in corneal scraping samples obtained from patients with microbial keratitis whose findings were not specific for HSV keratitis and to evaluate these particular cases with respect to clinical features and antiviral treatment results.

METHODS

Records of patients with microbial keratitis treated in a tertiary eye care hospital within the 3-year period were evaluated retrospectively. Real-time polymerase chain reaction (PCR) was used to identify HSV DNA. Smear slides were evaluated by light microscopy. Patients with typical presentations and histories of HSV keratitis were excluded.

RESULTS

Two hundred and seventy-six eyes of 276 patients were included in the study. HSV-1 DNA was detected in 25 eyes (9%). In these 25 eyes, the initial diagnosis was fungal or bacterial keratitis. The mean symptom duration was 20 ± 14 days (2-60 days). The risk factors were ocular surgery (20%), blepharitis (16%), trauma (8%) and contact lens wear (4%); however, the majority of patients did not have any specific cause for keratitis (52%). Clinical features were variable and not typical for any particular etiology. Culture and microscopic examinations revealed bacteria and/or fungi in 6 patients in addition to herpes infection. Antiviral treatment was successful in 72% of patients.

CONCLUSION

Herpetic corneal infections can present without typical dendritic or geographic ulcers and may be masked by other infections. Real-time PCR is a useful method for rapid and definitive diagnosis. HSV infection should be considered for microbial keratitis without specific risk factors, with negative culture results and poor response to antimicrobial agents.

Therapeutic penetrating keratoplasty for microbial keratitis in Taiwan from 2001 to 2014

PURPOSE

To study the surgical outcome of therapeutic penetrating keratoplasty (TPK) for medically uncontrolled microbial keratitis at a tertiary hospital in Taiwan over a 14-year period.

METHODS

This is a retrospective case series study. Patients who underwent TPK at National Taiwan University Hospital in 2001-2014 were included. Patients were divided into 3 diagnostic groups: bacterial keratitis, fungal keratitis, and acanthamoeba keratitis. Each of the following criteria was evaluated: graft clarity at 1 month and 1 year postoperatively, cure of the disease, and anatomical success rate.

RESULTS

A total of 107 TPKs were included. TPK eradicated the infection in 57/62 (91.9%) of bacterial keratitis, 33/41 (80.5%) of fungal keratitis, and 9/10 (90.0%) of acanthamoeba keratitis. 22/57 grafts (38.6%) of bacterial keratitis, 22/38 grafts (57.9%) of fungal keratitis, and 5/10 grafts (50.0%) of acanthamoeba keratitis remained clear at 1 year postoperatively. The 1-year graft survival rate did not significantly differ among these 3 groups. The leading causes of graft failure were late endothelial decompensation and graft reinfection. A higher percentage of graft clarity was achieved in grafts <8.5 mm in diameter than in larger grafts (55.4% vs. 31.4%, P = 0.027). Of the 14 patients with endophthalmitis at the time of TPK, the infection was successfully treated in 13 patients except 1 patient required evisceration.

CONCLUSION

TPK is valuable in the management of medically uncontrolled microbial keratitis, although the 1-year graft survival rate is unsatisfactory. TPK combined with intravitreal antibiotics and vitrectomy is also a beneficial treatment strategy for patients with endophthalmitis secondary to microbial keratitis.

Risk Factors of Microbial Keratitis in Uganda: A Case Control Study

Purpose: Microbial keratitis (MK), is a frequent cause of sight loss worldwide, particularly in low and middle-income countries. This study aimed to investigate the risk factors of MK in Uganda.Methods: Using a nested case control, we recruited healthy community controls for patients presenting with MK at the two main eye units in Southern Uganda between December 2016 and March 2018. Controls were individually matched for age, gender and village of the cases on a 1:1 ratio. We collected information on demographics, occupation, HIV and Diabetes Mellitus status. In STATA version 14.1, multivariable conditional logistic regression was used to generate odds ratios for risk factors of MK and a likelihood ratio test used to assess statistical significance of associations.Results: Two hundred and fifteen case-control pairs were enrolled. The HIV positive patients among the cases was 9% versus 1% among the controls, p = .0003. Diabetes 7% among the cases versus 1.4% among the controls, p = .012. Eye trauma was 29% versus 0% among the cases and controls. In the multivariable model adjusted for age, sex and village, HIV (OR 83.5, 95%CI 2.01-3456, p = .020), Diabetes (OR 9.38, 95% CI 1.48-59.3, p = .017) and a farming occupation (OR 2.60, 95%CI 1.21-5.57, p = .014) were associated with MK. Compared to a low socio-economic status, a middle status was less likely to be associated with MK (OR 0.29, 95%CI 0.09-0.89, p < .0001).Conclusion: MK was associated with HIV, Diabetes, being poor and farming as the main occupation. More studies are needed to explore how these factors predispose to MK.

Comparison of microbiome isolated from the conjunctiva, contact lens and lens storage case of symptomatic and asymptomatic contact lens users

BACKGROUND AND OBJECTIVES

Contact lenses (CLs) are increasingly being used for cosmetic or therapeutic purposes. Lack of compliance and poor hygiene towards lens care is strongly associated with microbial contamination and has been proved to result in eye infections. The present study was done to compare the microbial flora between symptomatic and asymptomatic contact lens users. The study also attempts to analyze the contact lens hygiene practices of CL users.

MATERIALS AND METHODS

Six samples each were collected from both the eyes, CLs and lens cases of 40 CL users (n=240) divided into two groups based on symptoms present asasymptomatic CL users and symptomatic CL users. Organisms were identified using standard microbiological techniques.

RESULTS

The proportion GNB obtained in symptomatic CL users was significantly higher when compared to asymptomatic CL users (p-value= <0.003). In 56.2% eyes, the microbial flora of conjunctiva was similar to either the contact lens isolate/storage case. Enterococcal microbial keratitis was seen in one case.

CONCLUSION

There was significant microbial contamination present in CL users despite compliance to contact lens hygiene practices. There were a significant number of bacteria (p-value <0.001) present which were resistant to ampicillin, amoxicillin-clavulanate, and cefotaxime in both the groups.

Photoactivated chromophore for infectious keratitis - Corneal cross-linking (PACK-CXL): A systematic review and meta-analysis

PURPOSE

To examine the efficacy of adjuvant photoactivated chromophore for infectious keratitis-corneal cross-linking (PACK-CXL) for the treatment of infectious keratitis (IK).

METHODS

Electronic databases, including MEDLINE, EMBASE and Cochrane Central, were searched for articles related to PACK-CXL. All clinical studies, including randomized controlled trials (RCTs), non-randomized controlled studies, case series and case reports, were included. A meta-analysis was further performed when there were sufficient similarities in the included RCTs. Primary outcome measure was time to complete corneal healing and secondary outcome measures included size of epithelial defect and infiltrate, corrected-distance-visual-acuity (CDVA), and adverse events.

RESULTS

Forty-six eligible studies (including four RCTs) with 435 patients were included. When compared to standard antimicrobial treatment (SAT) alone, adjuvant PACK-CXL resulted in shorter mean time to complete corneal healing (-7.44 days; 95% CI, -10.71 to -4.16) and quicker resolution of the infiltrate at 7 days (-5.49 mm²; 95% CI, -7.44 to -3.54) and at 14-30 days (-5.27 mm²; 95% CI, -9.12 to -1.41). There was no significant difference in the size of epithelial defect, CDVA and risk of adverse events. Evidence on the use of PACK-CXL in acanthamoeba and mixed IK was insufficient.

CONCLUSIONS

Our study demonstrates that adjuvant PACK-CXL expedites the healing of IK when compared to SAT alone (low-quality evidence). Further adequately powered, high-quality RCTs are required to fully ascertain the therapeutic effect of PACK-CXL.

Microbial Keratitis and Ocular Surface Disease: A 5-Year Study of the Microbiology, Risk Factors and Clinical Outcomes in Sydney, Australia

Purpose: To report the microbiological and clinical profiles, and outcomes of patients with microbial keratitis who had ocular surface disease (OSD) at the Sydney Eye Hospital, Australia over a 5-year period.Methods: A retrospective case-series study was conducted. Patients diagnosed with microbial keratitis who had a history of OSD (dry eye, blepharitis, Steven Johnson syndrome (SJS) and ocular cicatricial pemphigoid (OCP)) from 1^st January 2012 to 31^st December 2016 were identified from hospital coding and pathology data. Data were extracted from the medical records.Results: 189 eyes from 171 patients with a mean age of 60 ± 19 years (range 20-96 years) were included. OSD included blepharitis (79%), dry eye (25%), SJS (4%) and OCP (2%). Coagulase-negative Staphylococcus (CoNS) (48%) were the most common isolated microorganism, made up of mostly Staphylococcus epidermidis (n = 37, 48%), Staphylococcus capitis (n = 16, 21%), and Staphylococcus warneri (n = 10, 13%). Median visual acuity at initial presentation was 0.52 logMAR and 0.30 logMAR at final visit. Median healing time was 12 days (IQR 6-27). The most common initial antimicrobial treatment prescribed was a combination of topical fortified cephalothin and gentamicin (n = 65, 34%); or topical ofloxacin (n = 56, 30%). Complications occurred in 69 eyes (37%), mainly non or slow-healing epithelial defects (n = 53, 43%) or corneal perforations (n = 24, 20%); and were more common in the elderly (n = 48/69, 70%).Conclusion: Microbial keratitis can affect those with OSD. In our setting, CoNS were the main organisms identified. Furthermore, patients prescribed a combination therapy of fortified antibiotics had poorer outcomes compared to monotherapy fluoroquinolones.

Delay Along the Care Seeking Journey of Patients with Microbial Keratitis in Uganda

Purpose

To describe the care seeking journey and causes of delay among patients with Microbial Keratitis in Uganda.

Methods

A prospective cohort of patients presenting with microbial keratitis at the two main eye units in Southern Uganda (2016–2018). We collected information on demographics, home address, clinical history, and presentation pathway including, order of facilities where patients went to seek care, treatment advice, cost of care, and use of Traditional Eye Medicine. Presentation time was noted. We compared “direct” presenters versus “indirect” presenters and analysed predictors of delay.

Results

About 313 patients were enrolled. All were self-referred. Only 19% of the patients presented directly to the eye hospital. Majority (52%) visited one facility before presenting, 19% visited two facilities, 9% visited three facilities, and 2% visited four facilities. The cost of care increased with increase in the number of facilities visited. People in a large household, further distance from the eye hospital and those who used Traditional Eye Medicine were less likely to come directly to the eye hospital. Visiting another facility prior to the eye hospital and use of Traditional Eye Medicine aOR 1.58 (95%CI 1.03–2.43), p = .038 were associated with delayed presentation to the eye hospital.

Conclusion

This study provided information on patient journeys to seek care. Delay was largely attributable to having visited another health facility: a referral mechanism for microbial keratitis was non-existent. There is need to explore how these health system gaps can be strengthened.

Hand hygiene is linked to microbial keratitis and corneal inflammatory events

Lack of or inadequate hand washing is a risk factor in the development of contact lens related microbial keratitis and corneal inflammatory events. In the public health domain there is compelling evidence that proper hand washing with soap can save lives. The purpose of this review is to draw attention to some of the public health literature in support of hand washing and how education can influence patients' hand hygiene behavior. Contact lens wearers are also guilty of poor hand washing behavior but there is scant evidence that education of hand washing procedures of lens wearers alters patient non-compliance. It is well known that pathogenic microbial contamination of contact lenses, lens cases, care solutions and anterior ocular components have been found with contact lens wear. However while the originating source may be hands or water, it is most likely both of these. Besides proper hand washing this paper will include mitigating strategies for avoiding microbial contamination.

Impact of topical corticosteroid pretreatment on susceptibility of the injured murine cornea to Pseudomonas aeruginosa colonization and infection

Research with animal models of Pseudomonas aeruginosa keratitis has shown that use of a topical corticosteroid alone against an established infection can significantly increase the number of colonizing bacteria or worsen clinical disease. Moreover, retrospective analysis has suggested that corticosteroid use in humans is associated with an increased risk of keratitis in eyes with pre-existing disease. Thus, while corticosteroids are often used to reduce ocular inflammation in the absence of infection, the risk of opportunistic infection remains a concern. However, the effect of corticosteroids on the intrinsic barrier function of uninfected corneas is unknown. Here, we tested if short-term topical corticosteroid treatment of an uninfected murine cornea would increase susceptibility to P. aeruginosa colonization or infection after epithelial injury. Topical prednisolone acetate (1%) was administered to one eye of C57BL/6 mice three times a day for 3 days; control eyes were treated with sterile PBS. Prior to inoculation with a cytotoxic P. aeruginosa corneal isolate strain 6206, corneas were subject to superficial-injury by tissue paper blotting, or scratch-injured followed by 12 h of healing. Previously we have shown that blotting renders mouse corneas susceptible to P. aeruginosa adhesion, but not infection, while 12 h healing reduces susceptibility to infection after scratching. Corneas were evaluated at 48 h for bacterial colonization and microbial keratitis (MK). To monitor impact on wound healing, corneal integrity was examined by fluorescein staining immediately after scarification and after 12 h healing. For both the tissue paper blotting and scratch-injury models, there was no significant difference in P. aeruginosa colonization at 48 h between corticosteroid-pretreated eyes and controls. With the blotting model, one case of MK was observed in a control (PBS-pretreated) cornea; none in corticosteroid-pretreated corneas. With the 12 h healing model, MK occurred in 6 of 17 corticosteroid-pretreated eyes versus 2 of 17 controls, a difference not statistically significant. Corticosteroid-pretreated eyes showed greater fluorescein staining 12 h after scarification injury, but this did not coincide with increased colonization or MK. Together, these data show that short-term topical corticosteroid therapy on an uninfected murine cornea does not necessarily enhance its susceptibility to P. aeruginosa colonization or infection after injury, even when it induces fluorescein staining.

Acanthamoeba keratitis: An emerging disease among microbial keratitis in the Cap Bon region of Tunisia

INTRODUCTION

The aim of this study was to describe the prevalence of AK among microbial keratitis as well as their clinical features and to compare their risk factors to those of other infectious keratitis, over the last five years in a referral center in the region of Cap Bon, Tunisia, North Africa.

METHODS

A retrospective review of the charts of 230 patients (230 eyes) diagnosed with presumed infectious keratitis between January 2011 and December 2016 at the department of ophthalmology of the university hospital of Nabeul in Tunisia. After a detailed ocular examination using standard technique, corneal scrapes were performed under aseptic conditions from each ulcer. Plates were incubated at 30 °C and screened daily for Amoeba. The treatment was adjusted according to the results of microbiological findings and the response of initial treatment. The mean follow up was 11.4 months (1 month-26 months).

RESULTS

A total of 230 corneas were scraped. The prevalence of Acanthamoeba keratitis was 6% (14 cases of 230). All cases of Acanthamoeba keratitis with a history of contact lenses were diagnosed thanks to the test of Contact lenses, their cases or their storage solution, while their corneal scrapings were negative. The corneal scraping was positive for Acanthamoeba only in 4 cases of 14. Acanthamoeba was identified more in young patients (92.8%). Significantly, more patients (54 of 74; 73%) with fungal keratitis and Acanthamoeba keratitis (11 of14; 78.6%) were rural population The most cases of Acanthamoeba keratitis (10 of 14; 71.4%) used contact lenses. Ocular injury was identified in 4 cases of 14 AK (28,5%). Coexistent ocular disease was seen in seven cases of 14 (50%). Of the 230 microbial keratitis, an early diagnosis (≤30 days) was done in 200 cases (86.95%), while a late diagnosis (≥30 days) was made in 30 cases (13%). In AK, most cases (11 of 14; 78,5%) were diagnosed with a delay of more than 30 days. Slit-lamp examination showed stromal infiltrate in 12 cases (85,7%), hypopion in 2 cases (14,3%), immunitary ring in 2 cases (14,3%) and radial keratoneuritis in one case (7,1%).

CONCLUSION

Contact lenses were identified as the main risk factor of Acanthamoeba keratitis in our study. The diagnosis of AK should be considered in case of atypical keratitis especially among CL wearers in the rural regions of CapBon where the rules of hygiene are not respected.

Bacterial keratitis treated by strengthened antibiotic eye drops: An 18 months review of clinical cases and antibiotic susceptibilities

PURPOSE

To describe, in patients treated for infectious keratitis, the microorganisms identified and their antibiotic susceptibility over a period of 18 months.

METHOD

Retrospective, descriptive, non-comparative study. Medical and biological data were extracted from the patients' file treated with strengthened antibiotic eye drops at Angers University Hospital between January 2015 and June 2016. The main elements noted were the bacteria involved and their susceptibility to antibiotics. Patients' visual acuity at the start and end of treatment was compared.

RESULTS

Forty-eight patients were included. Almost one bacterium was identified in 31 patients, totalling 43 pathogens of 24 different species. The most frequently found microorganisms were Gram-positive cocci (55.8%), including Staphylococcus Aureus (14.0%) and Epidermidis (14.0%). All Gram-negative bacilli amounted to 30.2% of the identified bacteria, including 9.3% of Pseudomonas aeruginosa. None of the Gram-positive cocci were resistant to vancomycin and all Gram-negative bacilli were susceptible to ceftazidime and amikacin. Following treatment with at least one of the three antibiotic eye drops produced by our pharmacy (amikacin at 50mg/mL, ceftazidime at 50mg/mL and vancomycin at 25mg/mL), patients' visual acuity was significantly improved (P=0.043).

CONCLUSION

The study helped identify the bacterial ecology of patients admitted for infectious keratitis. Among the bacteria identified, none were found to be resistant to any of the three strengthened antibiotic eye drops produced by the hospital pharmacy. These eye drops allowed for a rapid and effective treatment of patients and the improvement of their visual acuity before even identifying the bacteria.

Ex vivo rabbit and human corneas as models for bacterial and fungal keratitis

PURPOSE

In the study of microbial keratitis, in vivo animal models often require a large number of animals, and in vitro monolayer cell culture does not maintain the three-dimensional structure of the tissues or cell-to-cell communication of in vivo models. Here, we propose reproducible ex vivo models of single- and dual-infection keratitis as an alternative to in vivo and in vitro models.

METHODS

Excised rabbit and human corneoscleral rims maintained in organ culture were infected using 10⁸ cells of Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans or Fusarium solani. The infection was introduced by wounding with a scalpel and exposing corneas to the microbial suspension or by intrastromal injection. Post-inoculation, corneas were maintained for 24 and 48 h at 37 °C. After incubation, corneas were either homogenised to determine colony-forming units (CFU)/cornea or processed for histological examination using routine staining methods. Single- and mixed-species infections were compared.

RESULTS

We observed a significant increase in CFU after 48 h compared to 24 h with S. aureus and P. aeruginosa. However, no such increase was observed in corneas infected with C. albicans or F. solani. The injection method yielded an approximately two- to 100-fold increase (p < 0.05) in the majority of organisms from infected corneas. Histology of the scalpel-wounded and injection models indicated extensive infiltration of P. aeruginosa throughout the entire cornea, with less infiltration observed for S. aureus, C. albicans and F. solani. The models also supported dual infections.

CONCLUSIONS

Both scalpel wounding and injection methods are suitable for inducing infection of ex vivo rabbit and human cornea models. These simple and reproducible models will be useful as an alternative to in vitro and in vivo models for investigating the detection and treatment of microbial keratitis, particularly when this might be due to two infective organisms.

Challenges of corneal infections

INTRODUCTION

Ocular infections remain an important cause of blindness worldwide and represent a challenging public health concern. In this regard, microbial keratitis due to fungal, bacterial, or viral infection can result in significant vision loss secondary to corneal scarring or surface irregularity. Left untreated corneal perforation and endophthalmitis can result, leading to loss of the eye. Rigorously studied animal models of disease pathogenesis have provided novel information that suggests new modes of treatment that may be efficacious clinically and emerging clinical data is supportive of some of these discoveries.

AREAS COVERED

This review focuses on advances in our understanding of disease pathogenesis in animal models and clinical studies and how these relate to improved clinical treatment. We also discuss a novel approach to treatment of microbial keratitis due to infection with these bacterial pathogens using PACK-CXL and recommend increased basic and clinical studies to address and refine the efficacy of this procedure.

EXPERT COMMENTARY

Because resistance to antibiotics has developed over time to these bacterial pathogens, caution must be exercised in treatment. Attractive novel modes of treatment that hold new promise for further investigation include lipid based therapy, as well as use of small molecules that bind deleterious specific host responsive molecules and use of microRNA based therapies.

The role of oral co-trimoxazole in treating Nocardia farcinica keratitis-a case report

Background

Nocardia farcinica is one of the more recently identified species of the Nocardia genus. Nocardia farcinica keratitis is a rare occurrence, with only eight previously reported cases. Semi-permeable rigid contact lens use was associated with one of these reported cases. We report the first case of extended wear soft contact-lens-related Nocardia farcinica keratitis and recommend a new treatment regime.

Findings

A 47-year-old lady presented with a right eye keratitis after wearing her extended wear soft contact lenses for five continuous weeks. There was no history of trauma or swimming with contact lenses in. Empirical ciprofloxacin and tobramycin eye drops were not tolerated due to ocular surface irritation on application; and instead, empirical treatment was with chloramphenicol and fortified gentamicin 1.5 % eye drops. Corneal scrapings grew Nocardia farcinica after 3 weeks—sensitive to amikacin and co-trimoxazole. Treatment was changed to amikacin 2.5 % eye drops, resulting in partial resolution of the corneal infiltrates. Oral co-trimoxazole 160/800 mg BD was added, due to cultured drug sensitivity and its high ocular penetration, with good results and a final right eye best-corrected visual acuity of 6/5.

Conclusion

Nocardia farcinica keratitis should be considered in the differential diagnosis of contact-lens-related keratitis. We report the first case occurring in association with extended wear soft contact lenses. Nocardia species can mimic fungal and Acanthamoeba keratitis. Treatment with oral co-trimoxazole has not been previously reported. This case demonstrates a role for co-trimoxazole in treating Nocardia farcinica keratitis based on cultured drug sensitivities.

The role of oral co-trimoxazole in treating Nocardia farcinica keratitis: a case report

Nocardia farcinica is one of the more recently identified species of the Nocardia genus. Nocardia farcinica keratitis is a rare occurrence, with only eight previously reported cases. Semi-permeable rigid contact lens use was associated with one of these reported cases. We report the first case of an extended wear soft contact lens-related Nocardia farcinica keratitis and recommend a new treatment regime. A 47-year-old lady presented with a right eye keratitis after wearing her extended wear soft contact lenses for five continuous weeks. There was no history of trauma or swimming with contact lenses in. Empirical ciprofloxacin and tobramycin eye drops were not tolerated due to ocular surface irritation on application, and instead, empirical treatment was with chloramphenicol and fortified gentamicin 1.5 % eye drops. Corneal scrapings grew Nocardia farcinica after 3 weeks—sensitive to amikacin and co-trimoxazole. Treatment was changed to amikacin 2.5 % eye drops, resulting in partial resolution of the corneal infiltrates. Oral co-trimoxazole 160 mg/800 mg BD was added, due to cultured drug sensitivity and its high ocular penetration, with good results and a final right eye best-corrected visual acuity of 6/5. Nocardia farcinica keratitis should be considered in the differential diagnosis of contact lens-related keratitis. We report the first case occurring in association with extended wear soft contact lenses. Nocardia species can mimic fungal and acanthamoeba keratitis. Treatment with oral co-trimoxazole has not been previously reported. This case demonstrates the role of co-trimoxazole in treating Nocardia farcinica keratitis based on cultured drug sensitivities.

Microbial Keratitis at an Urban Public Hospital: A 10-Year Update

Purpose

To review the epidemiology, risk factors, microbiologic spectrum, and treatment of microbial keratitis during a five-year period at an urban public hospital with comparison to similar findings a decade earlier at the same hospital.

Methods

Retrospective chart review in the 5-year interval 2009 through 2014 compared to previously reported cases 2000 through 2004 [Eye & Contact Lens 33(1): 45-49, 2007]. Comparative primary outcome measures included best-corrected visual acuity (BCVA), risk factors, culture and sensitivities, treatment, and complication rates.

Results

318 eyes with microbial keratitis were identified. Contact lens wear, ocular trauma, and ocular surface diseases were the most common risk factors. The culture and recovery rates were 73% and 66% respectively. Gram-positive organisms represented 46%, gram-negative organisms 39%, fungal organisms 15%, and Acanthamoeba <1% of corneal isolates. No common corneal pathogens were resistant to aminoglycosides or vancomycin. 48% of cases were initially treated with fortified antibiotics, 43% with fluoroquinolone monotherapy, and 6% with antifungals. 40% of cases received inpatient treatment. At resolution, average BCVA was 20/82 [logMAR 0.61] with 8% of cases resulting in light perception or worse vision. The perforation rate was 8%. 6% of cases underwent urgent penetrating keratoplasty and 4% of cases underwent urgent enucleation or evisceration. Compared to the prior study, significant differences were: (1) lower culture but higher recovery rates, (2) lower admission rate, (3) more contact lens-related cases of Pseudomonas ulcers, (4) lower resistance of coagulase-negative Staphylococcus to aminoglycoside antibiotics, (5) improved BCVA at resolution, and (6) lower associated complication rates.

Conclusion

Microbial keratitis remains a clinical challenge in the urban public hospital setting. In the past ten years, epidemiology has shifted towards greater contact lens wear with more Pseudomonal infections. Visual outcomes have not worsened despite a shift away from routine culture and inpatient care to fluoroquinolone monotherapy and outpatient management.