Antimicrobial resistance trends in bacterial keratitis over 5 years in Sydney, Australia

Perspectives on the Incidence of Acanthamoeba Keratitis: A Systematic Review and Meta-Analysis

TOPIC

To provide an overview on the incidence of Acanthamoeba keratitis (AK).

CLINICAL RELEVANCE

Although being a sight-threatening cause of infectious keratitis, a comprehensive assessment of the incidence of AK is lacking.

METHODS

Incidence of AK was computed as the number of eyes with AK per health care center, per year (annualized center incidence [ACI]). Two meta-analytical ratios also were calculated: (1) the ratio of eyes with AK to the count of eyes with nonviral microbial keratitis (MK) and (2) the ratio of eyes with AK to the overall population (i.e., the total number of people in a nation or region, as indicated by the authors in each study). Center was defined as the health care facility where the study took place. Actual and projected estimates of the number of eyes with AK in years were calculated multiplying the ratio of eyes with AK to the total population and the corresponding population estimates, sourced from the United Nations Population Prospects.

RESULTS

Overall, 105 articles were included, published between 1987 and 2022. The total number of eyes identified was 91 951, with 5660 eyes affected by AK and 86 291 eyes affected by nonviral MK. The median ACI was 1.9 eyes with AK per health care center per year (95% confidence interval [CI], 1.5-2.6 eyes), with no statistically significant differences among continents. The ratio of eyes with AK to the total number of eyes with MK was 1.52% (95% CI, 1.03%-2.22%), whereas the ratio of eyes with AK in relationship to the entire population was estimated at 2.34 eyes per 1 000 000 people (95% CI, 0.98-5.55 per 1 000 000 people). The projected increase in the numbers of eyes with AK indicated an increase of 18.5% (n = 15 355 eyes with AK) in 2053 and 25.5% (n = 16 253 eyes with AK) in 2073, compared with the baseline of 2023 (n = 12 953 eyes with AK).

DISCUSSION

Acanthamoeba keratitis emerged as a relatively low-incident disorder, and no significant differences in terms of its incidence were found among different continents.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Demographic and Microbiological Profile of Corneal Ulcers in Eastern India

PURPOSE

To evaluate the microbiological profile of corneal ulcers presenting at a tertiary care eye hospital in eastern Uttar Pradesh (UP), India.

METHODS

This retrospective, observational study included patients with corneal ulcers who underwent corneal scraping and microbiological examination of the sample from May 2014 to October 2023. The demographic details, predisposing factors, and clinical examination data of the patients were noted. Microbiology report of staining and culture (blood agar and Sabaraud's dextrose agar) of corneal scraping sample was analyzed in percentage. Reports of antimicrobial susceptibility testing were also noted and analyzed.

RESULTS

A total of 695 corneal scraping samples were examined during the study period. The mean age of the patients was 45.95 years. Among the patients, 412 (59.28%) were males and 283 (40.72%) were females. Among the patients, 402 (57.84%) belonged to an agricultural background. Trauma was the most common predisposing factor associated with 350 (50.36%) cases. The corneal scraping samples were stain-positive in 455 (65.47%) cases, of which, 130 (28.57%) were gram-positive and 325 (71.43%) were positive on potassium hydroxide (KOH) mount. Culture was positive in 306 (44.03%) cases, of which, bacterial isolates were found in 78 (25.49%), and fungal isolates were found in 228 (74.51%). Fusarium was the most common fungal isolate in 72 (31.58%) cases followed by Aspergillus in 60 (26.32%) cases. Among the bacterial isolates, Staphylococcus aureus was the most common in 20 (25.64%) cases followed by Pseudomonas and Streptococcus. The antimicrobial susceptibility testing showed that 47 (60.26%) of the bacterial isolates were sensitive to fluoroquinolones while the rest 31 (39.74%) were resistant. All the Staphylococcus aureus strains (including four cases of methicillin-resistant Staphylococcus aureus) were susceptible to vancomycin and linezolid, while 7 (35%) were resistant to moxifloxacin. None of the Pseudomonas strains were multidrug resistant. Among the fungal isolates, 220 (96.49%) were susceptible to voriconazole and 189 (82.89%) were sensitive to amphotericin B.

CONCLUSION

Fungal corneal ulcers are more common compared to bacterial ulcers in eastern India, particularly eastern UP and Bihar. This article highlights the importance of microbial testing and provides insight into the prevalent organisms and their antimicrobial susceptibility pattern in this geographic location, the knowledge of which will help clinicians in the appropriate management of these cases.

Ocular surface immune transcriptome and tear cytokines in corneal infection patients

Background

Microbial keratitis is one of the leading causes of blindness globally. An overactive immune response during an infection can exacerbate damage, causing corneal opacities and vision loss. This study aimed to identify the differentially expressed genes between corneal infection patients and healthy volunteers within the cornea and conjunctiva and elucidate the contributing pathways to these conditions' pathogenesis. Moreover, it compared the corneal and conjunctival transcriptomes in corneal-infected patients to cytokine levels in tears.

Methods

Corneal and conjunctival swabs were collected from seven corneal infection patients and three healthy controls under topical anesthesia. RNA from seven corneal infection patients and three healthy volunteers were analyzed by RNA sequencing (RNA-Seq). Tear proteins were extracted from Schirmer strips via acetone precipitation from 38 cases of corneal infection and 14 healthy controls. The cytokines and chemokines IL-1β, IL-6, CXCL8 (IL-8), CX3CL1, IL-10, IL-12 (p70), IL-17A, and IL-23 were measured using an antibody bead assay.

Results

A total of 512 genes were found to be differentially expressed in infected corneas compared to healthy corneas, with 508 being upregulated and four downregulated (fold-change (FC) <-2 or > 2 and adjusted p <0.01). For the conjunctiva, 477 were upregulated, and 3 were downregulated (FC <-3 or ≥ 3 and adjusted p <0.01). There was a significant overlap in cornea and conjunctiva gene expression in patients with corneal infections. The genes were predominantly associated with immune response, regulation of angiogenesis, and apoptotic signaling pathways. The most highly upregulated gene was CXCL8 (which codes for IL-8 protein). In patients with corneal infections, the concentration of IL-8 protein in tears was relatively higher in patients compared to healthy controls but did not show statistical significance.

Conclusions

During corneal infection, many genes were upregulated, with most of them being associated with immune response, regulation of angiogenesis, and apoptotic signaling. The findings may facilitate the development of treatments for corneal infections that can dampen specific aspects of the immune response to reduce scarring and preserve sight.

Antimicrobial resistance in ocular infection: A review

Antimicrobial resistance (AMR) is a global public health threat with significant impact on treatment outcomes. The World Health Organization's Global Action Plan on AMR recommended strengthening the evidence base through surveillance programs and research. Comprehensive, timely data on AMR for organisms isolated from ocular infections are needed to guide treatment decisions and inform researchers and microbiologists of emerging trends. This article aims to provide an update on the development of AMR in ocular organisms, AMR in bacterial ocular infections and on AMR stewardship programs globally. The most common ocular pathogens are Pseudomonas aeruginosa, Staphylococcus spp., Streptococcus pneumoniae, and Haemophilus influenzae in ocular infections. A variety of studies and a few surveillance programs worldwide have reported on AMR in these infections over time. Fluoroquinolone resistance has increased particularly in Asia and North America. For conjunctivitis, the ARMOR cumulative study in the USA reported a slight decrease in resistance to ciprofloxacin. For keratitis, resistance to methicillin has remained stable for S. aureus and CoNS, while resistance to ciprofloxacin has decreased for MRSA globally. Methicillin-resistance and multidrug resistance are also emerging, requiring ongoing monitoring. Antimicrobial stewardship (AMS) programmes have a critical role in reducing the threat of AMR and improving treatment outcomes. To be successful AMS must be informed by up-to-date AMR surveillance data. As a profession it is timely for ophthalmology to act to prevent AMR leading to greater visual loss through supporting surveillance programmes and establishing AMS.

Carboxylated nanofibrillated cellulose empowers moxifloxacin to overcome Staphylococcus aureus biofilm in bacterial keratitis

Bacterial keratitis is one of the vision-threatening ocular diseases that is increasing at an alarming rate due to antimicrobial resistance. One of the primary causes of antimicrobial resistance could be biofilm formation, which alters the mechanism and physiology of the microorganisms. Even a potent drug fails to inhibit biofilm due to the extracellular polysaccharide matrix surrounding the bacteria, inhibiting the permeation of drugs. Therefore, we aimed to develop carboxylated nanocellulose fibers loaded with moxifloxacin (Mox-cNFC) as a novel drug delivery system to treat bacterial corneal infection. Nanocellulose fibers were fabricated using a two-step method involving citric acid hydrolysis followed by TEMPO oxidation to introduce carboxylated groups (1.12 mmol/g). The Mox-cNFC particles showed controlled drug release till 40 h through diffusion. In vitro biofilm inhibition studies showed the particle's ability to disrupt the biofilm matrix and enhance the drug penetration to achieve optimal concentrations that inhibit the persister cells (without increasing minimum inhibitory concentration), thereby reducing the bacterial drug-resistant property. In vivo studies revealed the therapeutic potential of Mox-cNFC to treat Staphylococcus aureus-induced bacterial keratitis with once-a-day treatment, unlike neat moxifloxacin. Mox-cNFC could improve patient compliance by reducing the frequency of instillation and a controlled drug release to prevent toxicity.

Microbial keratitis and antibiotic sensitivity patterns: A retrospective analysis at a tertiary center in Central India

Purpose

To report on the microbiological profile and antibiotic sensitivity patterns of infectious keratitis at a tertiary center in central India.

Methods

The suspected case of severe keratitis underwent microbiological culture and identification using the VITEK 2 technique. Antibiotic susceptibility for different sensitivity and resistance patterns was analyzed. Demographics, clinical profile, and socioeconomic history was also documented.

Results

Culture was positive in 233/455 (51.2%) patients. Pure bacterial growth was present in 83 (35.62%) patients and pure fungus was present in 146 (62.66%) patients. The most common bacterial cause of infectious keratitis was Pseudomonas followed by Staphylococcus and Bacillus. Pseudomonas showed 65%-75% resistance against levofloxacin, ceftazidime, imipenem, gentamycin, ciprofloxacin, and amikacin. Staphylococcus showed 65%-70% resistance against levofloxacin, erythromycin, and ciprofloxacin, with Streptococcus being 100% resistant to erythromycin.

Conclusion

This study highlights the current trend of microbiological profiles of infectious keratitis and their antibiotic susceptibility at a rural setup in central India. Fungal predominance and increased resistance against the commonly used antibiotics were noted.

Bacterial Keratitis: Clinical Features, Causative Organisms, and Outcome During a 13-year Study Period

PURPOSE

This study aimed to review clinical features, causative organisms, complications, and outcome of bacterial keratitis cases at a tertiary eye hospital.

METHODS

A retrospective study was conducted on clinically diagnosed bacterial keratitis cases from 2007 to 2019. Poor outcome was flagged if any of the following was identified: final visual acuity (VA) worse than 20/200, decrease in VA (1 line or worse compared with presenting VA), corneal perforation, endophthalmitis, failed graft, or cases requiring enucleation or evisceration.

RESULTS

The study included 263 cases of bacterial keratitis with 169 cases (64.3%) of culture-positive bacterial keratitis. Gram-positive bacteria were found to be the causative organism in 106 cases (62.8%). The most common types were coagulase-negative staphylococci (23.1%) and Pseudomonas (23.1%). Culture-positive bacterial keratitis was associated with the development of anterior chamber reaction (≥1+) on multivariate analysis [adjusted odds ratio (OR): 3.03, confidence interval (CI): 1.23-7.45, P = 0.016]. The complications that occurred in the current cohort included visually significant scar (64.7%), perforation (10.8%), cataract (8.8%), nonhealing epithelial defects (8.0%), corneal neovascularization (4.9%), endophthalmitis (4.6%), and hypotony (1.5%). On multivariate analysis, diabetes mellitus (adjusted OR: 3.51, CI: 1.59-7.76, P = 0.002), poor presenting best-corrected VA (adjusted OR: 3.95, CI 1.96-7.96, P < 0.001), and positive cultures (adjusted OR: 2.36, CI: 1.11-5.00, P = 0.025) were associated with poor outcome.

CONCLUSIONS

Culture-negative keratitis had less severe infection and better outcomes when compared to culture-positive bacterial keratitis. Factors associated with poor outcome included diabetes, poor presenting VA, and positive cultures.

Recent advancements in nanotechnology-based bacteriophage delivery strategies against bacterial ocular infections

Antibiotic resistance is growing as a critical challenge in a variety of disease conditions including ocular infections leading to disastrous effects on the human eyes. Staphylococcus aureus (S. aureus) mediated ocular infections are very common affecting different parts of the eye viz. vitreous chamber, conjunctiva, cornea, anterior and posterior chambers, tear duct, and eyelids. Blepharitis, dacryocystitis, conjunctivitis, keratitis, endophthalmitis, and orbital cellulitis are some of the commonly known ocular infections caused by S. aureus. Some of these infections are so fatal that they could cause bilateral blindness like panophthalmitis and orbital cellulitis, which is caused by methicillin-resistant S. aureus (MRSA) and vancomycin-resistance S. aureus (VRSA). The treatment of S. aureus infections with known antibiotics is becoming gradually difficult because of the development of resistance against multiple antibiotics. Apart from the different combinations and formulation strategies, bacteriophage therapy is growing as an effective alternative to treat such infections. Although the superiority of bacteriophage therapy is well established, yet physical factors (high temperatures, acidic pH, UV-rays, and ionic strength) and pharmaceutical barriers (poor stability, low in-vivo retention, controlled and targeted delivery, immune system neutralization, etc.) have the greatest influence on the viability of phage virions (also phage proteins). A variety of Nanotechnology based formulations such as polymeric nanoparticles, liposomes, dendrimers, nanoemulsions, and nanofibres have been recently reported to overcome the above-mentioned obstacles. In this review, we have compiled all these recent reports and discussed bacteriophage-based nanoformulations techniques for the successful treatment of ocular infections caused by multidrug-resistant S. aureus and other bacteria.

A Pilot Study to Evaluate Genipin in Staphylococcus aureus and Pseudomonas aeruginosa Keratitis Models: Modulation of Pro-Inflammatory Cytokines and Matrix Metalloproteinases

Infectious keratitis is a vision-threatening microbial infection. The increasing antimicrobial resistance and the fact that severe cases often evolve into corneal perforation necessitate the development of alternative therapeutics for effective medical management. Genipin, a natural crosslinker, was recently shown to exert antimicrobial effects in an ex vivo model of microbial keratitis, highlighting its potential to serve as a novel treatment for infectious keratitis. This study aimed to evaluate the antimicrobial and anti-inflammatory effects of genipin in an in vivo model of Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa) keratitis. Clinical scores, confocal microscopy, plate count, and histology were carried out to evaluate the severity of keratitis. To assess the effect of genipin on inflammation, the gene expression of pro- and anti-inflammatory factors, including matrix metalloproteinases (MMPs), were evaluated. Genipin treatment alleviated the severity of bacterial keratitis by reducing bacterial load and repressing neutrophil infiltration. The expression of interleukin 1B (IL1B), interleukin 6 (IL6), interleukin 8 (IL8), interleukin 15 (IL15), tumor necrosis factor-α (TNF-α), and interferon γ (IFNγ), as well as MMP2 and MMP9, were significantly reduced in genipin-treated corneas. Genipin promoted corneal proteolysis and host resistance to S. aureus and P. aeruginosa infection by suppressing inflammatory cell infiltration, regulating inflammatory mediators, and downregulating the expression of MMP2 and MMP9.

Epidemiology and Economic Cost Analysis of Microbial Keratitis from a Tertiary Referral Hospital in Australia

Microbial keratitis is the most common cause of infective vision loss. The causative organism varies by region, and most cases require intensive antimicrobial therapy. The purpose of this study was to analyse the causative organisms of microbial keratitis, its presentation and economic burden from a tertiary referral hospital in Australia. A retrospective review of 160 cases of microbial keratitis was performed, over a 5-year period from 2015–2020. A wide variety of costs were considered to determine the economic burden, using standardized data from the Independent Hospital Pricing Authority and the cost of personal income loss. Our study showed the most commonly occurring pathogens were Herpes Simplex (16%), Staphylococcus aureus (15.1%) and Pseudomonas aeruginosa (14.3%). A total of 59.3% of patients were admitted, with a median length of admission of 7 days. Median cost for all presentations of microbial keratitis was AUD 8013 (USD 5447), with costs significantly increasing with admission. The total annual cost of microbial keratitis within Australia is estimated to be AUD 13.58 million (USD 9.23 million). Our findings demonstrate that microbial keratitis represents a significant economic burden for eye-related diseases and the key driving factor for the cost is the length of admission. Minimizing the duration of admission, or opting for outpatient management where appropriate, would significantly reduce the cost of treatment for microbial keratitis.

Ocular streptococcal infections: A clinical and microbiological review

Streptococcus is a diverse bacterial genus that is part of the ocular surface microbiome implicated in conjunctivitis, keratitis, endophthalmitis, dacryocystitis, and orbital cellulitis which can lead to decreased visual acuity and require surgical intervention. The pathophysiology of S. pneumoniae is well established and the role of the polysaccharide capsule, pneumolysin, neuraminidases, and zinc metalloproteinases in ocular infections described. Additionally, key virulence factors of the viridans group streptococci such as cytolysins and proteases have been outlined, but there is a paucity of research on the remaining streptococcus species. These virulence factors tend to result in aggressive disease. Clinically, S. pneumoniae is implicated in 2.7-41.2% of bacterial conjunctivitis cases, more predominant in the pediatric population, and is implicated in 1.8-10.7% of bacterial keratitis isolates. Streptococcus bacteria are significantly implicated in acute postoperative, post-intravitreal, and bleb-associated endophthalmitis, responsible for 10.3-37.5, 29.4, and 57.1% of cases, respectively. Group A and B streptococcus endogenous endophthalmitis is rare, but has a very poor prognosis. Inappropriate prescription of antibiotics in cases of non-bacterial aetiology has contributed to increasing resistance, and a clinical index is needed to more accurately monitor this. Furthermore, there is an increasing need for prospective, surveillance studies of antimicrobial resistance in ocular pathogens, as well as point-of-care testing using molecular techniques.

Hyaluronic acid association with bacterial, fungal and viral infections: Can hyaluronic acid be used as an antimicrobial polymer for biomedical and pharmaceutical applications?

The relationships between hyaluronic acid (HA) and pathological microorganisms incite new understandings on microbial infection, tissue penetration, disease progression and lastly, potential treatments. These understandings are important for the advancement of next generation antimicrobial therapeutical strategies for the control of healthcare-associated infections. Herein, this review will focus on the interplay between HA, bacteria, fungi, and viruses. This review will also comprehensively detail and discuss the antimicrobial activity displayed by various HA molecular weights for a variety of biomedical and pharmaceutical applications, including microbiology, pharmaceutics, and tissue engineering.

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.

The protective effect of URP20 on ocular Staphylococcus aureus and Escherichia coli infection in rats

BACKGROUND

Infectious keratitis, a medical emergency with acute and rapid disease progression may lead to severe visual impairment and even blindness. Herein, an antimicrobial polypeptide from Crassostrea hongkongensis, named URP20, was evaluated for its therapeutic efficacy against keratitis caused by Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) infection in rats, respectively.

METHODS

A needle was used to scratch the surface of the eyeballs of rats and infect them with S. aureus and E.coli to construct a keratitis model. The two models were treated by giving 100 μL 100 μM URP20 drops. Positive drugs for S. aureus and E. coli infection were cefazolin eye drops and tobramycin eye drops, respectively. For the curative effect, the formation of blood vessels in the fundus was observed by a slit lamp (the third day). At the end of the experiment, the condition of the injured eye was photographed by cobalt blue light using 5 μL of 1% sodium fluorescein. The pathological damage to corneal tissues was assessed using hematoxylin-eosin staining, and the expression level of vascular endothelial growth factor (VEGF) was detected by immunohistochemistry.

RESULTS

URP20 alleviated the symptoms of corneal neovascularization as observed by slit lamp and cobalt blue lamp. The activity of S. aureus and E.coli is inhibited by URP20 to protect corneal epithelial cells and reduce corneal stromal bacterial invasion. It also prevented corneal thickening and inhibited neovascularization by reducing VEGF expression at the cornea.

CONCLUSION

URP20 can effectively inhibit keratitis caused by E.coli as well as S. aureus in rats, as reflected by the inhibition of corneal neovascularization and the reduction in bacterial damage to the cornea.

Genomics of Staphylococcus aureus Strains Isolated from Infectious and Non-Infectious Ocular Conditions

Staphylococcus aureus is a major cause of ocular infectious (corneal infection or microbial keratitis (MK) and conjunctivitis) and non-infectious corneal infiltrative events (niCIE). Despite the significant morbidity associated with these conditions, there is very little data about specific virulence factors associated with the pathogenicity of ocular isolates. A set of 25 S. aureus infectious and niCIEs strains isolated from USA and Australia were selected for whole genome sequencing. Sequence types and clonal complexes of S. aureus strains were identified by using multi-locus sequence type (MLST). The presence or absence of 128 virulence genes was determined by using the virulence finder database (VFDB). Differences between infectious (MK + conjunctivitis) and niCIE isolates from USA and Australia for possession of virulence genes were assessed using the chi-square test. The most common sequence types found among ocular isolates were ST5, ST8 while the clonal complexes were CC30 and CC1. Virulence genes involved in adhesion (ebh, clfA, clfB, cna, sdrD, sdrE), immune evasion (chp, esaD, esaE, esxB, esxC, esxD), and serine protease enzymes (splA, splD, splE, splF) were more commonly observed in infectious strains (MK + conjunctivitis) than niCIE strains (p = 0.004). Toxin genes were present in half of infectious (49%, 25/51) and niCIE (51%, 26/51) strains. USA infectious isolates were significantly more likely to possess splC, yent1, set9, set11, set36, set38, set40, lukF-PV, and lukS-PV (p < 0.05) than Australian infectious isolates. MK USA strains were more likely to possesses yent1, set9, set11 than USA conjunctivitis strains (p = 0.04). Conversely USA conjunctivitis strains were more likely to possess set36 set38, set40, lukF-PV, lukS-PV (p = 0.03) than MK USA strains. The ocular strain set was then compared to 10 fully sequenced non-ocular S. aureus strains to identify differences between ocular and non-ocular isolates. Ocular isolates were significantly more likely to possess cna (p = 0.03), icaR (p = 0.01), sea (p = 0.001), set16 (p = 0.01), and set19 (p = 0.03). In contrast non-ocular isolates were more likely to possess icaD (p = 0.007), lukF-PV, lukS-PV (p = 0.01), selq (p = 0.01), set30 (p = 0.01), set32 (p = 0.02), and set36 (p = 0.02). The clones ST5, ST8, CC30, and CC1 among ocular isolates generally reflect circulating non-ocular pathogenic S. aureus strains. The higher rates of genes in infectious and ocular isolates suggest a potential role of these virulence factors in ocular diseases.

Infectious keratitis: A review

Globally, infectious keratitis is the fifth leading cause of blindness. The main predisposing factors include contact lens wear, ocular injury and ocular surface disease. Staphylococcus species, Pseudomonas aeruginosa, Fusarium species, Candida species and Acanthamoeba species are the most common causal organisms. Culture of corneal scrapes is the preferred initial test to identify the culprit organism. Polymerase chain reaction (PCR) tests and in vivo confocal microscopy can complement the diagnosis. Empiric therapy is typically commenced with fluoroquinolones, or fortified antibiotics for bacterial keratitis; topical natamycin for fungal keratitis; and polyhexamethylene biguanide or chlorhexidine for acanthamoeba keratitis. Herpes simplex keratitis is mainly diagnosed clinically; however, PCR can also be used to confirm the initial diagnosis and in atypical cases. Antivirals and topical corticosteroids are indicated depending on the corneal layer infected. Vision impairment, blindness and even loss of the eye can occur with a delay in diagnosis and inappropriate antimicrobial therapy.

Clinical characteristics of external bacterial ocular and periocular infections and their antimicrobial treatment patterns among a Ghanaian ophthalmic population

Empirical antimicrobial therapy is linked to a surge in antimicrobial resistant infections. However, an insight on the bacteria etiology of ocular infections is essential in the appropriation of choice of antimicrobial among clinicians, yet there remains a dearth of data from Ghana. We investigated the bacteria etiology of external ocular and periocular infections and antimicrobial treatment patterns among a Ghanaian ophthalmic population. A multicenter study design with purposive sampling approach was employed. Patients demographics and clinical data were collated using a pretested structure questionnaire. Cornea specimens and conjunctival swabs were obtained for bacterial isolation following standard protocols. About 95% (98/103) of ocular samples were positive for bacteria culture. The proportion of Gram-negative bacteria was 58.2%, and the predominant bacteria species were Pseudomonas aeruginosa 38.8% and Staphylococcus aureus 27.6%. Conjunctivitis 40.0% and keratitis 75.0% were mostly caused by Pseudomonas aeruginosa. The routinely administered antimicrobial therapy were polymyxin B 41.2%, neomycin 35.1% and ciprofloxacin 31.6%. Participants demographic and clinical characteristics were unrelated with positive bacteria culture (p > 0.05). Our results showed a markedly high burden of ocular bacterial infections and variations in etiology. Bacterial infection-control and antimicrobial agent management programs should be urgently institutionalized to prevent the emergence of resistant infections.

Outcomes of Microbial Keratitis Cases Resistant to Antimicrobials in Sydney, Australia

PURPOSE

The purpose of this study was to describe demographics, predisposing factors, clinical features, treatment, and outcomes of microbial keratitis cases resistant to antimicrobials.

METHODS

A retrospective case series was conducted. All patients with microbial keratitis resistant to antimicrobials who underwent a corneal scrape and culture from 2012 to December 2016 at the Sydney Eye Hospital were included. Cases were identified from pathology and hospital coding data. Coagulase-negative staphylococci (CoNS), Staphylococcus aureus (S. aureus), and Corynebacterium spp. resistant to cefalotin, chloramphenicol, ciprofloxacin, or gentamicin were analyzed.

RESULTS

One hundred fifteen episodes had a resistant CoNS, 24 S. aureus, and 12 Corynebacterium spp. Antimicrobial resistance was associated with older women (67%, median age 83 years) with Corynebacterium spp. (P < 0.001), corneal graft, and previous topical steroid use. Larger epithelial defects (P = 0.203) and infiltrates (P = 0.180) were more likely to be associated with Corynebacterium spp., but not statistically significant. At the initial and final visits, resistant S. aureus (75% vs. 67%) and Corynebacterium spp. (78% vs. 80%) cases were more likely to be classified as blind (>3/60) compared with CoNS (45% vs. 28%) (P = 0.011 vs. P = 0.004). Corneal perforation occurred more often in resistant S. aureus cases (P < 0.001), whereas slow and nonhealing epithelial defects needing other procedures were more likely to occur with resistant Corynebacterium spp. (P < 0.001).

CONCLUSIONS

Patients with resistant CoNS were younger and presented with smaller ulcers and moderate vision loss. Visual and clinical outcomes were significantly better for resistant CoNS than for those with resistant S. aureus or Corynebacterium spp.

Pathogens and Antibiotic Susceptibilities of Global Bacterial Keratitis: A Meta-Analysis

Bacterial keratitis (BK) is the most common type of infectious keratitis. The spectrum of pathogenic bacteria and their susceptibility to antibiotics varied with the different regions. A meta-analysis was conducted to review the global culture rate, distribution, current trends, and drug susceptibility of isolates from BK over the past 20 years (2000–2020). Four databases were searched, and published date was limited between 2000 and 2020. Main key words were “bacterial keratitis”, “culture results” and “drug resistance”. Forty-two studies from twenty-one countries (35 cities) were included for meta-analysis. The overall positive culture rate was 47% (95%CI, 42–52%). Gram-positive cocci were the major type of bacteria (62%), followed by Gram-negative bacilli (30%), Gram-positive bacilli (5%), and Gram-negative cocci (5%). Staphylococcus spp. (41.4%), Pseudomonas spp. (17.0%), Streptococcus spp. (13.1%), Corynebacterium spp. (6.6%) and Moraxella spp. (4.1%) were the most common bacterial organism. The antibiotic resistance pattern analysis revealed that most Gram-positive cocci were susceptive to aminoglycoside (86%), followed by fluoroquinolone (81%) and cephalosporin (79%). Gram-negative bacilli were most sensitive to cephalosporin (96%) and fluoroquinolones (96%), followed by aminoglycoside (92%). In Gram-positive cocci, the susceptibility trends of fluoroquinolones were decreasing since 2010. Clinics should pay attention to the changing trends of pathogen distribution and their drug resistance pattern and should diagnose and choose sensitive antibiotics based on local data.

Subpalpebral Antibiotic Lavage as Safe, Emergent, and Cost-Effective Management of Acute Infectious Keratitis Related to Contact Lens Overwear: Case Report and Literature Review

PURPOSE

The aim of this study is to describe the technique of subpalpebral antibiotic lavage (SAL), which is a highly therapeutic, efficient, and cost-effective method for managing severe bacterial keratitis.

METHODS

This case report describes a 26-year-old woman with severe bacterial keratitis in the right eye due to contact lens overwear, with progressive corneal thinning, a hypopyon, impending perforation, and marked visual loss to perception of light despite treatment with intensive topical antibiotics. This was managed with SAL that involves the insertion of a cannula transcutaneously into the upper conjunctival fornix to provide continuous antibiotic irrigation of the ocular surface.

RESULTS

By 11 weeks after presentation, the cornea and anterior chamber appeared clinically quiescent, and visual acuity improved to 20/40 corrected in the right eye.

CONCLUSIONS

Bacterial keratitis is a potentially blinding condition for which contact lens wear is an important risk factor. Most cases are successfully managed with topical medications; however, in cases of treatment failure, a second-line approach such as SAL can be sight-saving. SAL uses readily available equipment for the delivery of high concentrations of antibiotics to the ocular surface, thus increasing therapeutic efficacy and reducing nursing staff workload. Despite its advantages, the literature reveals apparent underutilization of this technique.

Paradox of complex diversity: Challenges in the diagnosis and management of bacterial keratitis

Bacterial keratitis continues to be one of the leading causes of corneal blindness in the developed as well as the developing world, despite swift progress since the dawn of the "anti-biotic era". Although, we are expeditiously developing our understanding about the different causative organisms and associated pathology leading to keratitis, extensive gaps in knowledge continue to dampen the efforts for early and accurate diagnosis, and management in these patients, resulting in poor clinical outcomes. The ability of the causative bacteria to subdue the therapeutic challenge stems from their large genome encoding complex regulatory networks, variety of unique virulence factors, and rapid secretion of tissue damaging proteases and toxins. In this review article, we have provided an overview of the established classical diagnostic techniques and therapeutics for keratitis caused by various bacteria. We have extensively reported our recent in-roads through novel tools for accurate diagnosis of mono- and poly-bacterial corneal infections. Furthermore, we outlined the recent progress by our group and others in understanding the sub-cellular genomic changes that lead to antibiotic resistance in these organisms. Finally, we discussed in detail, the novel therapies and drug delivery systems in development for the efficacious management of bacterial keratitis.

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.

Genipin in an Ex Vivo Corneal Model of Bacterial and Fungal Keratitis

Purpose

To determine whether genipin (a natural crosslinker) could reduce the colonization and proliferation of bacteria and fungi in an ex vivo model of corneal infection.

Methods

This study, using an ex vivo model of bacterial and fungal keratitis, investigated the antimicrobial efficacy of genipin crosslinking. Excised corneoscleral buttons were wounded by scalpel incision and subsequently infected with Staphylococcus aureus, Pseudomonas aeruginosa, or Candida albicans. After inoculation, corneas were treated with genipin for 24 hours at 37°C. Histologic examinations were carried out, and the number of viable colony-forming units (CFU)/cornea was determined.

Results

Genipin exerts bactericidal action against S. aureus and P. aeruginosa, as well as fungicidal action against C. albicans and significantly reduced the CFU compared to contralateral eyes that received saline treatment (P < 0.05).

Conclusions

These data identify genipin as a novel ocular antimicrobial agent that has the potential to be incorporated into the therapeutic armamentarium against microbial keratitis.

Translational Relevance

This study provided evidence for the antimicrobial and antifungal properties of genipin as an alternative crosslinker that could be used in the management of infectious keratitis.

Proteus mirabilis Keratitis: Risk Factors, Clinical Features, Treatment Outcomes, and Microbiological Characteristics

PURPOSE

To characterize the risk factors, clinical presentations, management choices, and outcomes of Proteus mirabilis keratitis.

METHODS

In this retrospective study, 26 culture-proven cases of P. mirabilis infections were diagnosed and treated between 1998 and 2019 at the University of Pittsburgh Medical Center. Medical records were available for 14 keratitis cases and were reviewed for demographic information, ocular risk factors, and treatment outcomes.

RESULTS

Sixteen eyes of 14 patients were included in the study. The average age was 47.8 ± 19.3 years, with a median follow-up time of 6 months. The most common ocular risk factors were poor ocular surface and contact lens use in 57.1% and 42.9% of cases, respectively. Eleven of the 14 patients (78.6%) had positive corneal cultures, and 13 of the 14 patients (92.9%) had positive conjunctiva or eyelid cultures. All isolates were susceptible to ciprofloxacin, ofloxacin, moxifloxacin, gatifloxacin, and cefazolin. Surgical intervention was required in 4 patients (28.6%). Average LogMAR visual acuity was 1.3 ± 1.0 at presentation and 0.9 6 ± 1.0 at the most recent follow-up visit.

CONCLUSIONS

Proteus mirabilis is an uncommon cause of microbial keratitis. Patients with poor ocular surface and those who use contact lens are at increased risk for developing this cause of keratitis. Empiric treatment with fortified antibiotics or fluoroquinolones seemed to provide effective coverage for P. mirabilis.

Antimicrobial nanomedicine for ocular bacterial and fungal infection

Ocular infection induced by bacteria and fungi is a major cause of visual impairment and blindness. Topical administration of antibiotics remains the first-line treatment, as effective eradication of pathogens is the core of the anti-infection strategy. Whereas, eye drops lack efficiency and have relatively low bioavailability. Intraocular injection may cause concurrent ocular damage and secondary infection. In addition, antibiotic-based management can be limited by the low sensitivity to multidrug-resistant bacteria. Nanomedicine is proposed as a prospective, effective, and noninvasive platform to mediate ocular delivery and combat pathogen or even resistant strains. Nanomedicine can not only carry antimicrobial agents to fight against pathogens but also directly active microbicidal capability, killing pathogens. More importantly, by modification, nanomedicine can achieve enhanced residence time and release time on the cornea, and easy penetration through corneal tissues into anterior and posterior segments of the eye, thus improving the therapeutic effect for ocular infection. In this review, several categories of antimicrobial nanomedicine are systematically discussed, where the efficiency and possibility of further embellishment and improvement to adapt to clinical use are also investigated. All in all, novel antimicrobial nanomedicine provides potent and prospective ways to manage severe and refractory ocular infections.

Infectious keratitis: an update on epidemiology, causative microorganisms, risk factors, and antimicrobial resistance

Corneal opacity is the 5th leading cause of blindness and visual impairment globally, affecting ~6 million of the world population. In addition, it is responsible for 1.5-2.0 million new cases of monocular blindness per year, highlighting an ongoing uncurbed burden on human health. Among all aetiologies such as infection, trauma, inflammation, degeneration and nutritional deficiency, infectious keratitis (IK) represents the leading cause of corneal blindness in both developed and developing countries, with an estimated incidence ranging from 2.5 to 799 per 100,000 population-year. IK can be caused by a wide range of microorganisms, including bacteria, fungi, virus, parasites and polymicrobial infection. Subject to the geographical and temporal variations, bacteria and fungi have been shown to be the most common causative microorganisms for corneal infection. Although viral and Acanthamoeba keratitis are less common, they represent important causes for corneal blindness in the developed countries. Contact lens wear, trauma, ocular surface diseases, lid diseases, and post-ocular surgery have been shown to be the major risk factors for IK. Broad-spectrum topical antimicrobial treatment is the current mainstay of treatment for IK, though its effectiveness is being challenged by the emergence of antimicrobial resistance, including multidrug resistance, in some parts of the world. In this review, we aim to provide an updated review on IK, encompassing the epidemiology, causative microorganisms, major risk factors and the impact of antimicrobial resistance.

Antimicrobial resistance of ocular microbes and the role of antimicrobial peptides

Isolation of antimicrobial-resistant microbes from ocular infections may be becoming more frequent. Infections caused by these microbes can be difficult to treat and lead to poor outcomes. However, new therapies are being developed which may help improve clinical outcomes. This review examines recent reports on the isolation of antibiotic-resistant microbes from ocular infections. In addition, an overview of the development of some new antibiotic therapies is given. The recent literature regarding antibiotic use and resistance, isolation of antibiotic-resistant microbes from ocular infections and the development of potential new antibiotics that can be used to treat these infections was reviewed. Ocular microbial infections are a global public health issue as they can result in vision loss which compromises quality of life. Approximately 70 per cent of ocular infections are caused by bacteria including Chlamydia trachomatis, Staphylococcus aureus, and Pseudomonas aeruginosa and fungi such as Candida albicans, Aspergillus spp. and Fusarium spp. Resistance to first-line antibiotics such as fluoroquinolones and azoles has increased, with resistance of S. aureus isolates from the USA to fluoroquinolones reaching 32 per cent of isolates and 35 per cent being methicillin-resistant (MRSA). Lower levels of MRSA (seven per cent) were isolated by an Australian study. Antimicrobial peptides, which are broad-spectrum alternatives to antibiotics, have been tested as possible new drugs. Several have shown promise in animal models of keratitis, especially treating P. aeruginosa, S. aureus or C. albicans infections. Reports of increasing resistance of ocular isolates to mainstay antibiotics are a concern, and there is evidence that for ocular surface disease this resistance translates into worse clinical outcomes. New antibiotics are being developed, but not by large pharmaceutical companies and mostly in university research laboratories and smaller biotech companies. Antimicrobial peptides show promise in treating keratitis.

Current understanding and therapeutic management of contact lens associated sterile corneal infiltrates and microbial keratitis

Contact lenses are widely prescribed in clinical practice with multiple applications and advantages. However, contact lenses can be associated with various complications which range from innocuous to severe. Clinicians thus not only need to possess the ability to prescribe the most appropriate contact lenses for each individual patient but also be able to recognise and manage any associated complications. This review examines the existing literature on the management of corneal infiltrative events associated with soft contact lenses, including microbial keratitis, particularly in the context of practising in Australia. The definitions and diagnosis of corneal infiltrative events, as well as the current understanding of their aetiologies, will be explored. The various aspects of a successful management will be discussed, including the applications of therapeutic agents such as antimicrobial and anti-inflammatory agents, the role of microbiological investigations, and strategies to improve long-term prognosis. The currently available evidence supporting management options will be presented, highlighting the relative abundance of high-level evidence on management protocols, antimicrobial selection and treatment duration for microbial keratitis; and the relative paucity of studies and trials for sterile corneal infiltrative events, despite this condition being much more commonly encountered in clinical practice.

Staphylococcus aureus Keratitis: Incidence, Pathophysiology, Risk Factors and Novel Strategies for Treatment

Bacterial keratitis is a devastating condition that can rapidly progress to serious complications if not treated promptly. Certain causative microorganisms such as Staphylococcus aureus and Pseudomonas aeruginosa are notorious for their resistance to antibiotics. Resistant bacterial keratitis results in poorer outcomes such as scarring and the need for surgical intervention. Thorough understanding of the causative pathogen and its virulence factors is vital for the discovery of novel treatments to avoid further antibiotic resistance. While much has been previously reported on P. aeruginosa, S. aureus has been less extensively studied. This review aims to give a brief overview of S. aureus epidemiology, pathophysiology and clinical characteristics as well as summarise the current evidence for potential novel therapies.

In Vitro and In Vivo Evaluation of Three Newly Isolated Bacteriophage Candidates, phiEF7H, phiEF14H1, phiEF19G, for Treatment of Enterococcus faecalis Endophthalmitis

Post-operative endophthalmitis caused by Enterococcus spp. progresses rapidly and often results in substantial and irreversible vision loss. Therefore, novel alternative treatments that are effective against enterococcal endophthalmitis are required. Bacteriophage therapy has the potential to be an optional therapy for infectious diseases. Therefore, we investigated the therapeutic potential of three newly isolated enterococcal phages, phiEF7H, phiEF14H1, and phiEF19G, in E. faecalis-induced endophthalmitis. These phages could lyse the broad-range E. faecalis, including strains derived from endophthalmitis and vancomycin-resistant E. faecalis in vitro, as determined by the streak test. Morphological and genomic analyses revealed that these phages were classified into the Herelleviridae genus Kochikohdavirus. The whole genomes of these phages contained 143,399, 143,280, and 143,400 bp, respectively. Endophthalmitis was induced in mice by injection of three strains of E. faecalis derived from post-operative endophthalmitis or vancomycin-resistant strains into the vitreous body. The number of viable bacteria and infiltration of neutrophils in the eye were both decreased by intravitreous injection of phiEF7H, phiEF14H1, and phiEF19G 6 h after injection of all E. faecalis strains. Thus, these results suggest that these newly isolated phages may serve as promising candidates for phage therapy against endophthalmitis.

Eye lymphatic defects induced by bone morphogenetic protein 9 deficiency have no functional consequences on intraocular pressure

Aqueous humor drainage is essential for the regulation of intraocular pressure (IOP), a major risk factor for glaucoma. The Schlemm's canal and the non-conventional uveoscleral pathway are known to drain aqueous humor from the eye anterior chamber. It has recently been reported that lymphatic vessels are involved in this process, and that the Schlemm's canal responds to some lymphatic regulators. We have previously shown a critical role for bone morphogenetic protein 9 (BMP9) in lymphatic vessel maturation and valve formation, with repercussions in drainage efficiency. Here, we imaged eye lymphatic vessels and analyzed the consequences of Bmp9 (Gdf2) gene invalidation. A network of lymphatic vessel hyaluronan receptor 1 (LYVE-1)-positive lymphatic vessels was observed in the corneolimbus and the conjunctiva. In contrast, LYVE-1-positive cells present in the ciliary bodies were belonging to the macrophage lineage. Although enlarged conjunctival lymphatic trunks and a reduced valve number were observed in Bmp9-KO mice, there were no morphological differences in the Schlemm's canal compared to wild type animals. Moreover, there were no functional consequences on IOP in both basal control conditions and after laser-induced ocular hypertonia. Thus, the BMP9-activated signaling pathway does not constitute a wise target for new glaucoma therapeutic strategies.

Topical Steroids as Adjunctive Therapy for Bacterial Keratitis: Evidence From a Retrospective Case Series of 313 Cases

PURPOSE

The aim of this study was to report topical steroid usage in bacterial keratitis and analyze the effects of steroids on patients' outcomes to the main causative organisms.

DESIGN

A retrospective case-series.

METHODS

This study included all patients with corneal scrape positive bacterial keratitis from January 2012 to December 2016 at the Sydney Eye Hospital, Sydney, Australia. Cases were identified from pathology results and hospital coding, and data collected from medical records.

RESULTS

A total of 313 eyes from 308 patients with a mean age of 51 years [interquartile range (IQR) 36-72] were included. Of these patients, 192 (61%) were treated with topical steroids. High-dose steroids were prescribed in 22 (11%) cases, regular-dose in 88 (46%), and low-dose in 82 (43%). The median time until the implementation of steroid use was 4 days (IQR 3-7). Patients prescribed with topical steroids had significantly longer healing times than the "no steroid" group (11 vs 6.5, P < 0.001). Patients with Pseudomonas aeruginosa keratitis and topical steroid use had worse clinical outcomes, with a higher proportion having longer healing times (P = 0.04) and corneal scarring (P = 0.02).

CONCLUSIONS

Adjuvant topical steroid therapy did not affect visual acuity, patient outcomes or the rate of adverse effects but may delay epithelial healing in bacterial keratitis in these patients. Topical steroids may have a differential effect depending on the specific causative organisms; however, a clinical trial is needed to assess this.

Microbial keratitis in Sydney, Australia: risk factors, patient outcomes, and seasonal variation

PURPOSE

To provide recent data on patient demographics, clinical profile and outcomes of patients with microbial keratitis over a 5-year period at the Sydney Eye Hospital, and to identify seasonal variations of the main causative organisms.

METHOD

A retrospective study of patients with a clinical diagnosis of microbial keratitis and corneal scrape performed between 1 January 2012 and 31 December 2016. Clinical information was gathered from medical records and pathology data.

RESULTS

One thousand fifty-two eyes from 979 patients with a mean age of 54.7 ± 21.5 years (range 18-100 years) were included. The majority of cases were bacterial (65%) followed by polymicrobial (2.4%), fungi (2.3%), and culture-negative (31%). Common risk factors for microbial keratitis were contact lens wear (63%) and previous topical steroid use (24%). Factors significantly associated with poor patient outcomes in the multivariate model were age, visual acuity, and epithelial defect size (p < 0.05). Patients with fungal or polymicrobial keratitis presented with worse clinical features at initial and final presentation (p < 0.05). There was a significant variation in the occurrence of Pseudomonas aeruginosa (p = 0.018) and fungal keratitis (predominately made up of Candida and Fusarium species) (p = 0.056) in the hottest seasons.

CONCLUSION

Poorer outcomes are more likely to be seen in older patients and those presenting with poor visual acuity and large epithelial defects at the initial presentation.