Role of liquid culture media in the laboratory diagnosis of microbial keratitis

Microbiological Profile of Culture-Positive Fungal Keratitis

PURPOSE

To examine the microbiological profile of cases of culture-positive fungal keratitis presenting to a tertiary eye care center in eastern India.

METHODS

Microbiology records of all culture-positive microbial keratitis patients presenting to L V Prasad Eye Institute, Bhubaneswar, between January 2020 and December 2021, were retrospectively reviewed. Collected data included smear results of culture-positive fungal or mixed infections, the species isolated, and the time taken for organisms to grow in each media.

RESULTS

Fungal keratitis formed 36% of all culture-positive microbial keratitis, whereas mixed infections (fungi and other organisms) formed 8.5%. The most common fungal species isolated was Fusarium spp. (25.8%). The most common bacteria involved in mixed infection with fungi was Staphylococcus spp. (54.8%). The positivity of potassium hydroxide+calcofluor white stain in detecting fungal filaments was 89.0% and that of Gram stain was 76.1%. Culture-positive cases of fungal keratitis showed most frequent growth on potato-dextrose agar (77.6%). A similar pattern was observed in culture-positive mixed infections (Sabouraud dextrose agar [SDA]: 84%). Most frequent growth of bacteria in mixed infections was seen in thioglycolate broth (54.7%). The shortest time to achieve significant fungal growth was observed in blood agar (BA) and chocolate agar (CA) (2.2/2.3 days, and 1.8/2 days for fungal keratitis and mixed infections, respectively). Filamentous hyaline fungi took the shortest time to achieve significant growth (2.8 days), whereas yeast forms took the longest (5 days).

CONCLUSION

This study highlights the importance of combined use of both solid and liquid culture media, especially potato dextrose agar (PDA)/SDA and CA, to arrive at a definitive diagnosis of fungal keratitis and possible bacterial co-infection, which forms a significant proportion of cases with fungal keratitis. In resource-poor laboratories, two culture media, either SDA or PDA, along with BA, may be plated to detect mixed infections. Examination of stained smears of corneal samples provides an inexpensive method of rapid diagnosis of fungal keratitis when culture media is not available.

Demographic and microbiological profile of corneal ulcer patients presenting at a tertiary healthcare center of Eastern India during the COVID era: A hospital-based cross-sectional study

Purpose

To determine the demographic and microbiological profile involved in the causation of corneal ulcers in Eastern India during the COVID era.

Method

Patients presenting with corneal ulcers fulfilling the inclusion and exclusion criteria were taken as the case. The study duration was from January 2021 to December 2021. Socio-demographic details and information about risk factors were noted. A detailed corneal examination followed by corneal scraping was performed for microbiological evaluation.

Results

In 1 year, 99 infective corneal ulcer patients were evaluated. Farmers (24.2%) were found to be maximally affected by corneal ulcers. The peak in cases was recorded from October to December (38.4%). Ocular trauma was the commonest risk factor (42.4%). The majority (80.8%) of patients were already on some topical antimicrobials. 22.2% of samples showed fungal filaments on KOH mount; 54.5% of these cases turned out to be culture-positive. 17.56% of KOH-negative samples turned out to be culture-positive (fungal). Overall, the culture positivity rate was 28.28% out of which fungal isolates were 89.28% and bacterial isolates were 10.72%. Fusarium species were identified as the most common organism contributing 42.85%, followed by Aspergillus fumigatus (14.28%). 10.72% of cases were culture positive for Pseudomonas aeuroginosa.

Conclusion

Trauma with the organic matter was the predominant cause of fungal keratitis. In this study, fungal keratitis was found to be more common. Fusarium was the most common isolate.

Impact of Sample Collection Order on the Diagnostic Performance of Metagenomic Deep Sequencing for Infectious Keratitis

PURPOSE

The purpose of this article was to evaluate the impact of sample collection order on the diagnostic yield of metagenomic deep sequencing (MDS) for determining the causative pathogen in infectious keratitis.

METHODS

We performed a cross-sectional diagnostic test evaluation among subjects with infectious keratitis at Aravind Eye Hospital in Madurai, India. All subjects underwent corneal scrapings of the affected eye to obtain potassium hydroxide smear, Gram stain, bacterial culture, and fungal culture, in this order. The order of MDS specimen collection relative to smear and culture samples was randomized and served as the primary predictor. Outcomes included the normalized copy number of pathogenic RNA detected by MDS, the proportion of MDS samples that were diagnostic, and the agreement of MDS results with cultures.

RESULTS

MDS samples from 46 subjects with corneal ulcers were evaluated. MDS was positive in 33 subjects (76%) and had 74% overall agreement with culture results. There was no association between order of MDS sample collection and normalized copy number of genetic material detected (P = 0.62) or the likelihood of MDS positivity (P = 0.46). However, the likelihood of agreement between MDS and cultures decreased when MDS corneal swabs were collected after other diagnostic corneal scrapings (P = 0.05).

CONCLUSIONS

The overall yield of MDS for detecting the cause of infectious keratitis was not affected by sample collection order. However, diagnostic agreement between MDS and cultures decreased when MDS samples were collected after other specimens. Additional investigation is warranted to determine whether this represents increased sensitivity of MDS compared with cultures or higher susceptibility to contaminants.

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.

Diagnostic methods for the etiological assessment of infectious corneal pathology (Review)

Infectious keratitis is a leading cause of visual morbidity, including blindness, all across the globe, especially in developing countries. Prompt and adequate treatment is mandatory to maintain corneal integrity and to recover the best possible final visual acuity. Although in most of the cases practitioners chose to employ empirical broad-spectrum antimicrobial medication that is usually effective, in some instances, they face the need to identify the causative agent to establish the appropriate therapy. An extensive search was conducted on published literature before December 2020 concerning the main laboratory investigations used to identify the microbial agents found in infectious keratitis, their indications, advantages, and disadvantages, as well as the results reported by other studies concerning different diagnostic tools. At present, the gold standard for diagnosis is still considered to be the isolation of microorganisms in cultures, along with the examination of smears, but other newer techniques, such as polymerase chain reaction (PCR), next-generation sequencing (NGS), and in vivo confocal microscopy (IVCM) have gained popularity in the last decades. Currently, these newer methods have proved to be valuable adjuvants in making the diagnosis, but technological advances hold promise that, in the future, these methods will have increased performance and availability, and may become the new gold standard, replacing the classic cultures and smears.

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

Purpose

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

Methods

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

Results

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

Conclusion

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

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

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

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.

Diagnostic armamentarium of infectious keratitis: A comprehensive review

Infectious keratitis (IK) represents the leading cause of corneal blindness worldwide, particularly in developing countries. A good outcome of IK is contingent upon timely and accurate diagnosis followed by appropriate interventions. Currently, IK is primarily diagnosed on clinical grounds supplemented by microbiological investigations such as microscopic examination with stains, and culture and sensitivity testing. Although this is the most widely accepted practice adopted in most regions, such an approach is challenged by several factors, including indistinguishable clinical features shared among different causative organisms, polymicrobial infection, long diagnostic turnaround time, and variably low culture positivity rate. In this review, we aim to provide a comprehensive overview of the current diagnostic armamentarium of IK, encompassing conventional microbiological investigations, molecular diagnostics (including polymerase chain reaction and mass spectrometry), and imaging modalities (including anterior segment optical coherence tomography and in vivo confocal microscopy). We also highlight the potential roles of emerging technologies such as next-generation sequencing, artificial intelligence-assisted platforms. and tele-medicine in shaping the future diagnostic landscape of IK.

The Spectrum of Microbial Keratitis: An Updated Review

Background:

In microbial keratitis, infection of the cornea can threaten vision through permanent corneal scarring and even perforation resulting in the loss of the eye. A literature review was conducted by Karsten, Watson and Foster (2012) to determine the spectrum of microbial keratitis. Since this publication, there have been over 2600 articles published investigating the causative pathogens of microbial keratitis.

Objective:

To determine the current spectrum of possible pathogens implicated in microbial keratitis relative to the 2012 study.

Methods:

An exhaustive literature review was conducted of all the peer-reviewed articles reporting on microbial pathogens implicated in keratitis. Databases including MEDLINE, EMBASE, Scopus and Web of Science were searched utilising their entire year limits (1950-2019).

Results:

Six-hundred and eighty-eight species representing 271 genera from 145 families were implicated in microbial keratitis. Fungal pathogens, though less frequent than bacteria, demonstrated the greatest diversity with 393 species from 169 genera that were found to cause microbial keratitis. There were 254 species of bacteria from 82 genera, 27 species of amoeba from 11 genera, and 14 species of virus from 9 genera, which were also identified as pathogens of microbial keratitis.

Conclusion:

The spectrum of pathogens implicated in microbial keratitis is extremely diverse. Bacteria were most commonly encountered and in comparison, to the review published in 2012, further 456 pathogens have been identified as causative pathogens of microbial keratitis. Therefore, the current review provides an important update on the potential spectrum of microbes, to assist clinicians in the diagnosis and treatment of microbial keratitis.

Management of infective corneal ulcers in a high-income developing country

Microbial keratitis is a major risk for corneal blindness worldwide. We aimed to study the clinical presentation and outcome of hospitalized patients having infective corneal ulcers.All patients who were diagnosed as microbial keratitis and were admitted to Al-Ain Hospital during the period July 2011-Dec 2016 were retrospectively studied. Patients' demography, predisposing factors, symptoms and signs at presentation, time to presentation after onset of symptoms, microbial isolates, hospital stay, and visual acuity (VA) outcome were studied.74 patients with corneal ulcers were hospitalized. 79.7% were males. The median (range) age was 44 years (1-91). 36.5% had trauma as a risk factor. The main presenting symptoms were pain (90.5%), red eye (79.7%), and decreased vision (63.5%). All patients had stromal infiltrate while 39.2% had hypopyon at presentation. The average time from the start of the symptoms to hospital presentation was 11 (1-90) days. The mean (range) hospital stay was 10.6 (1-60) days. Forty eyes were culture positive. Bacteria were identified in 27 eyes and fungus in 16. Pseudomonas aeruginosa (9 eyes) and Staphylococcus epidermis (5 eyes) were the most common bacterial islolates. Aspergillus (6 eyes) was the most common fungus species. 95.2% of the bacterial isolates were susceptible to the quinolone antibiotics group. Twenty eight (51.9%) patients had a vision worse than 6/60 in the affected eye.Corneal ulcer poses a significant threat to the sight of an affected eye. Trauma was the most common risk factor for corneal ulcers. Usage of eyes personal protective equipment for high risk occupations and earlier accessibility to health care may reduce the impact of corneal ulcers in our community.

An Omics Approach to Diagnosing or Investigating Fungal Keratitis

Fungal keratitis (FK) is one of the most severe corneal infectious diseases. FK often leads to poor visual prognosis and thus requires accurate diagnosis. Conventional approaches, including clinical diagnoses, smears, and cultures, often fail to provide reliable diagnostic value. Omics approaches, such as those using genomic, metagenomic, and tear proteomic data sources, provide promising features for improving the diagnosis and monitoring the progression of FK. Genomic approaches are based mainly on detecting amplicons of ribosomal RNA genes, and internal transcribed spacers are gradually gaining popularity in clinical practices. A metagenomic approach based on 16S rRNA genes may help monitor the dynamic change of conjunctival microbiota associated with an FK event, whereas that based on shot-gun and 18S rRNA target enrichment sequencing could have the potential to diagnose FK using clinical samples. A tear proteomic approach may provide comprehensive information about ocular surface defense and injury during FK. Representative up- and down-regulated proteins during FK could also be used as biomarkers to determine the clinical course and develop a treatment strategy in different stages of FK. Consequently, a personalized tear proteomic approach will soon play a key role in FK management.

Molecular Bioburden of the Lens Storage Case for Contact Lens-Related Keratitis

PURPOSE

To elucidate the bioburden of a lens care system in patients with contact lens (CL)-related keratitis.

METHODS

In this prospective case-control study, the CL storage case was used as the target of bioburden assessment. Participants were CL wearers with (n = 26) or without (n = 24) keratitis in southern Taiwan. The case fluid sample was consecutively collected and assessed using a dot hybridization assay (DHA) for bioburden assessment. The DHA was composed of 3 universal bacterial probes for detecting all bacteria, genus-specific probes for Pseudomonas and Acinetobacter, and 1 probe for Acanthamoeba. The receiver operating characteristic curve was used to analyze the differentiating performance of a probe.

RESULTS

The storage case bioburden was significantly higher in those with CL-related keratitis than in control subjects; patients with CL-related keratitis had stronger standardized signals in all universal bacterial probes. Moreover, in the cases of these patients, the bioburden was significantly heavier in confirmed infectious keratitis than in presumed noninfectious keratitis. Receiver operating characteristic analysis showed that stronger signals in all 3 universal bacterial probes and the Pseudomonas probe might suggest that the wearers have infectious keratitis. Only the storage case of the Acanthamoeba keratitis case showed positive detection by the Acanthamoeba probe.

CONCLUSIONS

A heavier bioburden in the lens storage case was associated with a higher risk of CL-related keratitis and infectious keratitis. Inappropriate maintenance of the CL will lead to microbial contamination and transfer the pathogen onto the ocular surface causing keratitis accordingly. The DHA assessment for the lens storage case might provide an alternative way to differentiate infectious from noninfectious CL-related keratitis.

A dot hybridization assay for the diagnosis of bacterial keratitis

Purpose

To evaluate a bacterial dot hybridization (BDH) assay for the diagnosis of bacterial keratitis (BK).

Methods

Sixty-one qualified corneal scrapings from 61 patients with suspected microbial keratitis were collected consecutively and prospectively. Among the 61 patients, 16 cases were BK and 45 cases were non-BK, including fungal keratitis, viral keratitis, parasitic keratitis, and non-microbial keratitis. Molecular diagnosis of BK in these corneal scrapes was performed using the BDH assay with three universal bacterial probes (PB1, PB2, and PB3) and three genus-specific probes (Aci, Klb, and Psu) to detect Acinetobacter, Klebsiella, and Pseudomonas, respectively. Signals were standardized after grayscale image transformation for objective validation using receiver operating characteristic (ROC) curves.

Results

The standardized intensities for the three universal probes differed statistically significantly between the BK group and the non-BK group. Based on the ROC curves, the sensitivities of PB1, PB2, and PB3 were 81.3%, 81.3%, and 93.8%, and the specificities were 71.1%, 88.9%, and 91.1%, respectively. The sensitivity and specificity of the Psu probe were 92% and 100%, respectively, while those of the Aci and Klb probes could not be estimated because there were no BK cases caused by Acinetobacter spp. or Klebsiella spp.

Conclusions

The BDH assay is an effective molecular approach to improve the diagnosis of BK. Because the bias from bacterial contamination on the ocular surface can be minimized with signal standardization, the assay has the potential to be adopted for routine clinical practice.

Microbiological profile of corneal ulcer cases diagnosed in a tertiary care ophthalmological institute in Nepal

Background

Corneal ulcer, a major cause of monocular blindness in developing countries has consistently been listed as the major cause of blindness and visual disability in many of the developing nations in Asia, Africa and the Middle East, ranking second only to cataract. This study was carried out to determine the microbiological profile of corneal ulcer cases diagnosed among patients visiting Tilganga Institute of Ophthalmology (TIO), Nepal.

Methods

A total of 101 corneal scrapping samples were tested for routine culture and antibiotic susceptibility at the pathology department of TIO Nepal from April to October 2014. Microorganisms were identified by using standard microbiological procedures following the manual of American Society for Microbiology (ASM) and their antibiotic susceptibility test, performed by Kirby-Bauer disc diffusion method in conformity with the CLSI guideline.

Results

Out of 101 samples analyzed, 44.6% (45/101) showed positive growth with bacterial isolates i.e., 56% (25/45), more prevalent than fungus i.e., 44% (20/45). Among bacteria Streptococcus pneumoniae (31.1%, N = 14) was isolated in highest number whereas Fusarium (13.4%, N = 6) was the most common fungus species. Pseudomonas aeruginosa was the only Gram negative bacteria isolated from corneal ulcer cases. All bacterial isolates were found to be susceptible to the quinolone group of antibiotics (moxifloxacin followed by ofloxacin and ciprofloxacin).

Conclusions

These findings showcase the current trend in the microbiological etiology of corneal ulcer in Nepal, which have important public health implications for the treatment as well as prevention of corneal ulceration in the developing world.

Ventriculostomy-related infections: The performance of different definitions for diagnosing infection

INTRODUCTION

Comparison of rates of ventriculostomy-related infections (VRIs) across institutions is difficult due to the lack of a standard definition. We sought to review published definitions of VRI and apply them to a test cohort to determine the degree of variability in VRI diagnosis.

MATERIALS AND METHODS

We conducted a PubMed search for definitions of VRI using the search strings "ventriculostomy-related infection" and "ventriculostomy-associated infection." We applied these definitions to a test cohort of 18 positive cerebrospinal fluid (CSF) cultures taken from ventriculostomies at two institutions to compare the frequency of infection using each definition.

RESULTS

We found 16 unique definitions of VRI. When the definitions were applied to the test cohort, the frequency of infection ranged from 22 to 94% (median 61% with interquartile range (IQR) 56-74%). The concordance between VRI diagnosis and treatment with VRI-directed antibiotics for at least seven days ranged from 56 to 89% (median: 72%, IQR: 71-78%).

CONCLUSIONS

The myriad of definitions in the literature produce widely different frequencies of infection. In order to compare rates of VRI between institutions for the purposes of qualitative metrics and research, a consistent definition of VRI is needed.

Filamentous fungal infections of the cornea: a global overview of epidemiology and drug sensitivity

Fungal keratitis is a serious suppurative, usually ulcerative corneal infection which may result in blindness or reduced vision. Epidemiological studies indicate that the occurrence of fungal keratitis is higher in warm, humid regions with agricultural economy. The most frequent filamentous fungal genera among the causal agents are Fusarium, Aspergillus and Curvularia. A more successful therapy of fungal keratitis relies on precise identification of the pathogen to the species level using molecular tools. As the sequence analysis of the internal transcribed spacer (ITS) region of the ribosomal RNA gene cluster (rDNA) is not discriminative enough to reveal a species-level diagnosis for several filamentous fungal species highly relevant in keratitis infections, analysis of other loci is also required for an exact diagnosis. Molecular identifications may also reveal the involvement of fungal species which were not previously reported from corneal infections. The routinely applied chemotherapy of fungal keratitis is based on the topical and systemic administration of polyenes and azole compounds. Antifungal susceptibility testing of the causal agents is of special importance due to the emergence and spread of resistance. Testing the applicability of further available antifungals and screening for new, potential compounds for the therapy of fungal keratitis are of highlighted interest.

A year of cornea in review: 2013

PURPOSE

The goal of this study was to provide an update of significant corneal literature published in 2013.

DESIGN

This study is a systematic literature review.

METHODS

We conducted a systematic review of the English-language literature published from January 1, 2013, to December 31, 2013, using the following PubMed search and Medical Subject Headings terms: cornea transplantation, keratoplasty, Descemet membrane endothelial keratoplasty, Descemet stripping endothelial keratoplasty, cross linking, pre-Descemet's layer, Rho-associated kinase, keratoprosthesis, infectious keratitis, corneal dystrophy, corneal astigmatism, and keratoconus.

RESULTS

This review summarizes relevant and innovative original articles, review articles, and novel techniques from the following journals: American Journal of Ophthalmology, British Journal of Ophthalmology, Cornea, Graefe's Archive for Clinical and Experimental Ophthalmology, Investigative Ophthalmology & Visual Science, JAMA Ophthalmology, Journal of Cataract and Refractive Surgery, Journal of Refractive Surgery, and Ophthalmology. Case reports, abstracts, letters to the Editor, and unpublished work were excluded, as well as articles e-published ahead of print in 2012 that were discussed in the previous review. One hundred twenty-seven articles met the criteria for this review.

CONCLUSIONS

This review summarizes significant cornea-related literature from 2013.