Corneal cross linking and infectious keratitis: a systematic review with a meta-analysis of reported cases

Immediate postoperative keratitis caused by Rhizopus species following standard CXL for keratoconus: A case report and literature review

PURPOSE

To report the first case of Rhizopus sp keratitis in a 15-year-old male patient who had undergone a conventional Epi-off CXL procedure for progressive keratoconus.

METHODS

A 15-year-old male studying at school presented with defective vision in both eyes recently. He was diagnosed with progressive keratoconus in the right eye more than left eye. After the conventional CXL procedure, the patient developed corneal ulcer on third postoperative day.

RESULTS

The microbiological diagnosis of both BCL and ulcer revealed Rhizopus sp. The patient responded to topical antifungals, and the ulcer entirely healed with a large central scar.

CONCLUSION

Rhizopus keratitis is rare in a healthy individual. Ours is the first case report of Rhizopus keratitis in patient undergone CXL.

Photoactivated chromophore-corneal cross-linking accelerates corneal healing in fungal keratitis: an updated meta-analysis

AIM

To determine the effectiveness and safety of photoactivated chromophore-corneal cross-linking (PACK-CXL) adjuvant in infectious keratitis by April 5, 2022.

METHODS

We searched randomized controlled trials (RCTs) comparing standard antibiotic treatment (SAT) plus PACK-CXL to SAT in infectious keratitis in Embase, MEDLINE with PubMed, Web of Science, and Cochrane Library. We independently screened and extracted data using predesigned tables. Cochrane's risk-of-bias tool was utilized to examine the quality of RCTs. A random-effects model was employed to determine the overall effect size of the meta-analyses. Grading of Recommendations, and Assessment, Development and Evaluations (GRADE) was also performed to examine the quality of evidence.

RESULTS

Seven eligible RCTs with 283 patients were acquired. Adjuvant PACK-CXL reduced the time needed to perform corneal healing in fungal keratitis (- 1.33 months; 95% CI, - 1.83 to - 0.42, I2 = 0%, P < 0.05) as compared to SAT alone. The risks of adverse events were not significantly different both in fungal and bacterial keratitis. Due to the substantial heterogeneity among studies, such as population, the type and severity of infectious keratitis, drug regimens of SAT, PACK-CXL protocol, and the judgment of subjective outcomes, the evidence grade was low.

CONCLUSION

Adjuvant PACK-CXL accelerates fungal keratitis healing as compared to SAT alone. But more rigorous RCTs are required to determine the clinical effectiveness and safety.

The novel role of lymphatic vessels in the pathogenesis of ocular diseases

Historically, the eye has been considered as an organ free of lymphatic vessels. In recent years, however, it became evident, that lymphatic vessels or lymphatic-like vessels contribute to several ocular pathologies at various peri- and intraocular locations. The aim of this review is to outline the pathogenetic role of ocular lymphatics, the respective molecular mechanisms and to discuss current and future therapeutic options based thereon. We will give an overview on the vascular anatomy of the healthy ocular surface and the molecular mechanisms contributing to corneal (lymph)angiogenic privilege. In addition, we present (i) current insights into the cellular and molecular mechanisms occurring during pathological neovascularization of the cornea triggered e.g. by inflammation or trauma, (ii) the role of lymphatic vessels in different ocular surface pathologies such as dry eye disease, corneal graft rejection, ocular graft versus host disease, allergy, and pterygium, (iii) the involvement of lymphatic vessels in ocular tumors and metastasis, and (iv) the novel role of the lymphatic-like structure of Schlemm's canal in glaucoma. Identification of the underlying molecular mechanisms and of novel modulators of lymphangiogenesis will contribute to the development of new therapeutic targets for the treatment of ocular diseases associated with pathological lymphangiogenesis in the future. The preclinical data presented here outline novel therapeutic concepts for promoting transplant survival, inhibiting metastasis of ocular tumors, reducing inflammation of the ocular surface, and treating glaucoma. Initial data from clinical trials suggest first success of novel treatment strategies to promote transplant survival based on pretransplant corneal lymphangioregression.

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.

Fungal Keratitis and Corneal Perforation as a Rare Complication of Corneal Collagen Cross-Linking Treatment

PURPOSE

The aim of this study was to report a case of fungal keratitis with subsequent corneal perforation after corneal collagen cross-linking (CXL) treatment performed for keratoconus.

CASE REPORT

A 20-year-old woman presented with redness and discharge in the left eye. She had a history of bilateral CXL procedure performed for keratoconus elsewhere 4 days earlier. The visual acuity was hand motion in the left eye. Slit-lamp examination revealed extended corneal melting with surrounding infiltrates. The patient was hospitalized, and corneal epithelial scraping samples were sent for microbiological assessment. In the meantime, empirical antibiotic therapy (fortified topical antibiotics: vancomycin 50 mg/mL, ceftazidime 50 mg/mL, and fluconazole 2 mg/mL q1 hour) was initiated. In direct microscopy of the corneal scraping, septate hyaline fungal hyphae were detected and topical fluconazole was switched to topical voriconazole (10 mg/mL). Three days after hospitalization, corneal melting progressed to perforation and corneal suturing with 10-0 monofilament was performed to reform the anterior chamber. Complete resolution of keratitis with residual scarring was noticed in 2 weeks. Three months later, penetrating keratoplasty was performed to obtain better visual acuity.

CONCLUSIONS

CXL with riboflavin has become a common procedure to prevent keratoconus progression by strengthening the biomechanical specialties of the cornea. Although the treatment itself has been used in the management of microbial keratitis and related corneal melting, fungal keratitis and corneal perforation after a CXL procedure for keratoconus might also be detected. Clinicians should be aware of this rare but devastating complication of CXL treatment and start prompt treatment when suspected.

Photoactivated Chromophore Corneal Collagen Cross-Linking for Infectious Keratitis (PACK-CXL)-A Comprehensive Review of Diagnostic and Prognostic Factors Involved in Therapeutic Indications and Contraindications

Infectious keratitis is a severe infection of the eye, which requires urgent care in order to prevent permanent complications. Typical cases are usually diagnosed clinically, whereas severe cases also require additional tools, such as direct microscopy, corneal cultures, molecular techniques, or ophthalmic imaging. The initial treatment is empirical, based on the suspected etiology, and is later adjusted as needed. It ranges from topical administration of active substances to oral drugs, or to complex surgeries in advanced situations. A novel alternative is represented by Photoactivated Chromophore Corneal Collagen Cross-Linking (PACK-CXL), which is widely known as a minimally invasive therapy for corneal degenerations. The purpose of this review is to identify the main diagnostic and prognostic factors which further outline the indications and contraindications of PACK-CXL in infectious keratitis. Given the predominantly positive outcomes in the medical literature, we ponder whether this is a promising treatment modality, which should be further evaluated in a systematic, evidence-based manner in order to develop a clear treatment protocol for successful future results, especially in carefully selected cases.

Review of the literature on the currently available evidence for the management of infectious keratitis with PACK-CXL

Infectious keratitis (IK) is one of the most common causes of monocular blindness worldwide, especially in developing countries and may account for 5.1%-32.3% of all indications for penetrating keratoplasty (PK). However, performing a therapeutic PK on a "hot eye" is associated with a higher incidence of IK recurrence and graft rejection. Standard treatment includes antimicrobials (ATM) and, once the causative pathogen has been identified, must be continued with targeted treatment, depending on antibiogram sensitivity. However, appearance of multiresistant strains to ATM is progressively increasing at an alarming rate. Besides that, the diversity of the causative microorganisms (bacteria, fungi, parasites, viruses) may hinder the clinical diagnosis and secondarily the proper treatment from the beginning. It is estimated that only 50% of eyes will have a good visual result if the correct therapy is delayed. All these factors make the identification of alternatives to ATM treatment of paramount importance. Due to the ATM properties of photoactivated chromophore (riboflavin, RB) and ultraviolet (UV) light of wavelength (λ) 200-400 nanometers (nm), used in multiple medical and non-medical applications for disinfection, photoactivated chromophore for corneal cross-linking (CXL) of IK (PACK-CXL), as an addition to the therapeutic arsenal for the management of IK has been proposed. It must be differentiated from CXL used for the management of progressive keratoconus (KC). The objective of this review is to update the available evidence on the efficacy and safety of PACK-CXL in IKs.

Corneal Collagen Cross-Linking Inhibits Corneal Blood and Lymphatic Vessels Temporarily in Alkali-Burned Rabbits

PURPOSE

This study aimed to explore whether corneal cross-linking (CXL) could regress corneal blood vessels (CBV) and corneal lymphatic vessels (CLV) in alkali-burned rabbits.

METHODS

A total of 80 rabbits 2-3 months old weighing 1.5-2.0 kg were randomly divided into four groups: CXL7 group; CTL7 group; CXL14 group; and CTL14 group. Then, 3% sodium pentobarbital 1 ml/kg and tetracaine eye drop 5 g/L were administered before surgery. NaOH 2 mol/L was topically applied to the central cornea to establish the alkali burning model. Then CXL was administered within 2 h in groups CXL7 and CXL14. Corneal opacity and edema, CBV and CLV volume, cluster differentiation 31 (CD31), and lymphatic vessel endothelial receptor 1 (LYVE-1) expression levels were analyzed on days 7 and 14.

RESULTS

CXL reduced cornea opacity, CNV, and CLV volumes on day 7 in alkali-burned rabbits. However, CNV and CLV volumes were increased on day 14. CXL also showed down- and upregulation of CD31 and LYVE-1 expression levels on days 7 and 14, respectively.

CONCLUSIONS

CXL effectively regulated CBV and CLV in alkali-burned rabbits. The transient angioregression and lymphangioregression induced by CXL may be potentially helpful in vascularized high-risk eyes.

Double-masked, sham and placebo-controlled trial of corneal cross-linking and topical difluprednate in the treatment of bacterial keratitis: Steroids and Cross-linking for Ulcer Treatment Trial (SCUT II) study protocol

Introduction

Although antibiotics are successful at achieving microbiological cure in infectious keratitis, outcomes are often poor due to corneal scarring. Ideal treatment of corneal ulcers would address both the infection and the inflammation. Adjunctive topical steroid treatment may improve outcomes by reducing inflammation. Corneal cross-linking (CXL) is a novel prospective therapy that may simultaneously reduce both inflammatory cells and bacterial pathogens. The purpose of this study is to determine differences in 6-month visual acuity between standard medical therapy with antibiotics versus antibiotics with adjunctive early topical steroid therapy versus antibiotic treatment plus CXL and early topical steroids.

Methods and analysis

This international, randomised, sham and placebo-controlled, three-arm clinical trial randomises patients with smear positive bacterial ulcers in a 1:1:1 fashion to one of three treatment arms: (1) topical 0.5% moxifloxacin plus topical placebo plus sham CXL; (2) topical 0.5% moxifloxacin plus difluprednate 0.05% plus sham CXL; or (3) the CXL group: topical 0.5% moxifloxacin plus difluprednate 0.05% plus CXL.

Ethics and dissemination

We anticipate that both adjunctive topical steroids and CXL will improved best spectacle corrected visual acuity and also reduce complications such as corneal perforation and the need for therapeutic penetrating keratoplasty. This study will comply with the NIH Data Sharing Policy and Policy on the Dissemination of NIH-Funded Clinical Trial Information and the Clinical Trials Registration and Results Information Submission rule. Our results will be disseminated via ClinicalTrials.gov website, meetings and journal publications. Our data will also be available on reasonable request.

Trial registration number

NCT04097730.

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.

Infectious keratitis after corneal crosslinking: systematic review

Corneal crosslinking is a U.S. Food and Drug Administration--approved therapy to stiffen the cornea and prevent progression of corneal ectasia in patients with keratoconus. The standard procedure involves removal of the corneal epithelium (epithelial-off) prior to treatment. Variations to the standard procedure include accelerated crosslinking and transepithelial procedures. This study reviewed what is known regarding the risk for infection after epithelial-off crosslinking, the spectrum of pathogens, and clinical outcomes. 26 publications were identified. All eyes were fit with a bandage contact lens postoperatively. Available data indicate that the overall frequency of infectious keratitis after epithelium-off crosslinking is low. Bacterial infections are the most common, with a mean time of presentation of 4.8 days postoperatively. The use of steroids and bandage contact lenses in the immediate postoperative period and/or a history of atopic or herpetic disease were associated with infection. These patients require intense postoperative care with prophylactic antiviral therapy when appropriate.

Polymicrobial Keratitis: Risk Factors, Clinical Characteristics, Bacterial Profile, and Antimicrobial Resistance

OBJECTIVE

To describe clinical characteristics, complications, and the most prevalent microorganisms causing polymicrobial keratitis and their antibiotic sensitivities.

METHODS

A cross-sectional study including a consecutive analysis of patient's records with a diagnosis of bacterial keratitis with a positive culture and antibiogram report were included. Patients were grouped into those having monomicrobial and polymicrobial infection. Features studied included demographic and clinical characteristics, risk factors, Gram stain, cultures, and antibiotic sensitivity.

RESULTS

We included 656 patients; in 31.5% more than one microorganism was found. Seven hundred and twenty-three gram-positive bacteria were isolated, and 336 (46.5%) had polymicrobial keratitis. One hundred sixty-one gram-negative bacteria were isolated, and 99 (61.5%) from polymicrobial keratitis. Fourteen (0.60%) patients presented ring infiltrate, and 10 (71.42%) of those patients had polymicrobial keratitis (X2 10.654, P=0.001). Multivariate analysis showed that patients with history of contact lens use (odds ratio [OR] of 1.78, P=0.042), coexistent autoimmune disease (OR 4.64, P=0.03), irregular edges of the infiltrate (OR 2.06, P=0.005), and ring infiltrate (OR 6.034, P=0.005) have a higher risk for developing polymicrobial infection. In the polymicrobial group, gram-positive and gram-negative organisms showed a high sensitivity to Netilmicin.

CONCLUSIONS

We found a high incidence of polymicrobial keratitis. Our results suggest that it should be suspected in patients with a history of contact lens use, coexistent autoimmune disease, infiltrates with indistinct edges, and ring infiltrates. Sensitivities to moxifloxacin are lower than those reported in previous studies, but sensitivity to Netilmicin is higher.

High Fluence Increases the Antibacterial Efficacy of PACK Cross-Linking

PURPOSE

Photoactivated chromophore for keratitis cross-linking (PACK-CXL) is used as an adjunct therapy to antibiotic medication in infectious keratitis. This experimental study aimed at quantifying the PACK-CXL efficacy as a function of UV fluence using several bacterial strains and irradiated volumes.

METHODS

Six distinct bacterial strains, including standardized strains and clinically isolated strains from patients with keratitis, were analyzed. Bacterial concentrations between 10 and 10 cells/mL were used (simulating small corneal ulcers). Volumes of either 11 μL (≈285 μm stromal thickness) or 40 μL (≈1000 μm stromal thickness) were irradiated within a microtiter plate at different fluences (5.4-27 J/cm) and irradiances (3, 9 and 18 mW/cm). The ratio of bacterial killing (B†) was determined to evaluate the antimicrobial efficacy of PACK-CXL.

RESULTS

B† was similar (51 ± 11%) in bacterial concentrations between 10 and 10 per ml. In 11 μL volume, Staphylococcus aureus (SA) 8325-4 ATCC 29213, Bacillus subtilis (BS) 212901, and Pseudomonas aeruginosa (PA) 2016-866624 were most sensitive to PACK-CXL at 5.4 J/cm (on average B† = 49 ± 8%), whereas Klebsiella oxytoca (KO) 2016-86624 (B† = 25%) was least sensitive. When irradiating a larger volume, B† was on average lower in 40 μL (19 ± 18%), compared with 11 μL (45 ± 17%, P < 0.001). By contrast, applying a higher UV fluence increased B† of SA ATCC 29213, from 50% at 5.4 J/cm to 92% at 10.8 J/cm, to 100% at 16.2 J/cm and above.

CONCLUSIONS

Applying higher UV fluences substantially increases the bacterial killing rates. Safety limits for clinical application require further investigation.

Accelerated corneal collagen cross-linking in clinical management of infectious keratitis

Objective

To evaluate the clinical efficacy of corneal collagen cross-linking (CXL) in the treatment of infectious corneal diseases.

Methods

This study retrospectively analyzed the clinical efficacy of CXL in 65 eyes with infectious keratitis in Jinan Second People’s Hospital from December 2016 to June 2018. During 6 months of follow-up after CXL treatment, the results of confocal microscopy and anterior segment optical coherence tomography, as well as visual acuity and corneal biomechanical parameters, were recorded in detail.

Results

In general, the overall cure rate was 93.85%; no corneal endothelial dysfunction was encountered in any patients. After 6 months of follow-up, the visual acuity of cured patients was significantly enhanced, while corneal thickness was significantly reduced. Hyphae growth of patients with fungal keratitis was completely inhibited at 1 month postoperatively. Furthermore, corneal biomechanical parameters (i.e., central corneal thickness, deformation amplitude, and pachymetry intraocular pressure) were significantly improved after surgery, compared with baseline measurements.

Conclusion

Accelerated CXL may be an effective adjuvant treatment for infectious keratitis.

Accelerated Corneal Cross-linking as an Adjunct Therapy in the Management of Presumed Bacterial Keratitis: A Cohort Study

PURPOSE

To compare the outcomes of accelerated photoactivated chromophore for keratitis corneal cross-linking (PACK-CXL) as an adjunct treatment for bacterial keratitis (PACK-CXL plus standard antibiotic therapy) for patients receiving only standard antibiotic therapy.

METHODS

Retrospective cohort study of outcomes of patients with moderate infectious presumed bacterial keratitis (ulcer diameter 2 to 7 mm and stromal depth < 300 µm) were compared before and after initiation of a new treatment protocol of PACK-CXL in addition to standard antibiotic treatment.

RESULTS

A total of 70 eyes of 70 patients were included: 39 eyes in the PACK-CXL plus antibiotic (PACK-ABX) group and 31 eyes in the antibiotic only (ABX) control group. The PACK-ABX group showed shorter times to complete reepithelialization (9.3 ± 6.0 vs 16.0 ± 12.7 days, P = .01) and did not require tectonic emergency keratoplasty (0% versus 19.4%, P = .006). The PACK-ABX group also showed a higher percentage of eyes with complete reepithelialization in 6 days or less (46.2% vs 6.5%, P < .001) and a trend for shorter hospitalizations (6.3 ± 5.0 vs 8.5 ± 4.5 days, P = .06). A multivariate analysis controlling for age showed that PACK-ABX treatment remained significantly associated with early ulcer reepithelialization (odds ratio = 0.09, 95% confidence interval = 0.02 to 0.48, P = .005).

CONCLUSIONS

This study validates previous findings regarding the use of accelerated PACK-CXL in the treatment of bacterial keratitis. Adding PACK-CXL improved clinical outcomes (reducing healing time) when compared to antibiotics alone. [J Refract Surg. 2020;36(4):258-264.].

Photoactivated Chromophore for Keratitis-Corneal Collagen Cross-Linking (PACK-CXL) Improves Outcomes of Treatment-Resistant Infectious Keratitis

Purpose

To investigate the efficacy of photoactivated chromophore corneal collagen cross-linking (PACK)-CXL in the management of treatment-resistant infectious keratitis.

Design

Observational cohort study.

Participants

Forty-two eyes from 41 patients with treatment-resistant infectious keratitis.

Methods

Eyes underwent PACK-CXL treatment with the Dresden modified protocol in addition to standard antimicrobial therapy. The primary endpoint was the size of the corneal ulcer. Descriptive statistics, Wilcoxon rank test, McNemar test and Spearman correlation coefficient were used for statistical analysis, and p values lower than 0.05 were considered statistically significant.

Results

Success rate at third postoperative month was of 90.5%. Statistical analyses showed a significant effect of (PACK)‑CXL with standard antimicrobial therapy to reduce corneal ulcer size (p=0.031).

Conclusion

As adjuvant therapy to standard antimicrobial treatment, PACK-CXL improves the outcomes in patients with treatment-resistant corneal ulcers.

Photobiomodulation of the Visual System and Human Health

Humans express an expansive and detailed response to wavelength differences within the electromagnetic (EM) spectrum. This is most clearly manifest, and most studied, with respect to a relatively small range of electromagnetic radiation that includes the visible wavelengths with abutting ultraviolet and infrared, and mostly with respect to the visual system. Many aspects of our biology, however, respond to wavelength differences over a wide range of the EM spectrum. Further, humans are now exposed to a variety of modern lighting situations that has, effectively, increased our exposure to wavelengths that were once likely minimal (e.g., “blue” light from devices at night). This paper reviews some of those biological effects with a focus on visual function and to a lesser extent, other body systems.

[Application of visible longwave radiation for inactivation of microorganisms]

PURPOSE

To perform a comparative assessment of the bactericidal and fungicidal effects of various parts of the radiation spectrum (Ultraviolet A, red, green and blue).

MATERIAL AND METHODS

The study included strains of the most clinically significant microorganisms, which are the most common causes of purulent keratitis - S. aureus, P. aeruginosa and fungi C. albicans. After populating the surface of Petri dishes uniformly with microorganisms of each culture, on four out of the five specimens the central zone of the surface with a diameter of 1 cm was irradiated with light of different spectrum - from ultraviolet to red, with a total radiation energy density of 5.4 J/cm². One specimen remained as the control subject. After irradiation, scanning electron microscopy with lanthanides contrasting (SEMLC) was used to evaluate the total metabolic activity, the activity of the efflux systems and the morphological characteristics of the microorganisms.

RESULTS

The damaging effect of visible spectrum light and UVA radiation on S. aureus, P. aeruginosa and C. albicans cultures was proved by SEMLC. Green spectrum emission with a wavelength of 500 nm had the highest antimicrobial activity. It was manifested by a decrease in the overall level of metabolic activity (from 40-63 c.u. to 26-37 c.u. (S. aureus (p<0.01), P. aeruginosa (p<0.01) and C. albicans (p<0.05)), as well as a 2-fold increase in the proportion of S. aureus cells with active efflux systems.

CONCLUSION

SEMLC allows evaluation of parameters of the microorganisms` state: morphological (form and size) and functional (general metabolic activity, activation of efflux systems). Investigation of S. aureus, P. aeruginosa and C. albicans cultures using SEMLC demonstrated the antimicrobial activity of green spectrum radiation of 500 nm wavelength. This will serve as a basis for further research and development of a method of treating infectious keratitis using green light.

Cross-Linking Assisted Infection Reduction (CLAIR): A Randomized Clinical Trial Evaluating the Effect of Adjuvant Cross-Linking on Bacterial Keratitis

PURPOSE

To determine whether there is a benefit to adjuvant corneal cross-linking (CXL) for bacterial keratitis.

METHODS

This is an outcome-masked, randomized controlled clinical trial. Consecutive patients presenting with a smear-positive bacterial ulcer at Aravind Eye Hospitals at Madurai, Pondicherry, and Coimbatore in India were enrolled. Study eyes were randomized to topical moxifloxacin 0.5% or topical moxifloxacin 0.5% plus CXL. The primary outcome of the trial was microbiological cure at 24 hours on repeat culture. Secondary outcomes included best spectacle corrected visual acuity at 3 weeks and 3 months, percentage of study participants with epithelial healing at 3 weeks and 3 months, infiltrate and/or scar size at 3 weeks and 3 months, 3-day smear and culture, and adverse events.

RESULTS

Those randomized to CXL had 0.60 decreased odds of culture positivity at 24 hours (95% confidence interval [CI]: 0.10-3.50; P = 0.65), 0.9 logarithm of the minimum angle of resolution lines worse visual acuity (95% CI: -2.8 to 4.6; P = 0.63), and 0.41-mm larger scar size (95% CI: -0.48 to 1.30; P = 0.38) at 3 months. We note fewer corneal perforations or need for therapeutic penetrating keratoplasty in the CXL group.

CONCLUSIONS

We were unable to confirm a benefit to adjuvant CXL in the primary treatment of moderate bacterial keratitis. However, CXL may reduce culture positivity and complication rates; therefore, a larger trial to fully evaluate this is warranted.

TRIAL REGISTRATION

NCT02570321.

Corneal collagen cross-linking for bacterial infectious keratitis

BACKGROUND

Infectious keratitis is an infection of the cornea that can be caused by bacteria, viruses, fungi, protozoa, or parasites. It may be associated with ocular surgery, trauma, contact lens wear, or conditions that cause deficiency or loss of corneal sensation, or suppression of the immune system, such as diabetes, chronic use of topical steroids, or immunomodulatory therapies. Photoactivated chromophore for collagen cross-linking (PACK-CXL) of the cornea is a therapy that has been successful in treating eye conditions such as keratoconus and corneal ectasia. More recently, PACK-CXL has been explored as a treatment option for infectious keratitis.

OBJECTIVES

To determine the comparative effectiveness and safety of PACK-CXL with standard therapy versus standard therapy alone for the treatment of bacterial keratitis.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Trials Register) (2019, Issue 7); Ovid MEDLINE; Embase.com; PubMed; Latin American and Caribbean Health Science Information database (LILACS); ClinicalTrials.gov; and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP). We did not use any date or language restrictions in the electronic search for trials. We last searched the electronic databases on 8 July 2019.

SELECTION CRITERIA

We included randomized controlled trials (RCTs), quasi-RCTs, and controlled clinical trials (CCTs) of PACK-CXL for bacterial keratitis. We included quasi-RCTs and CCTs as we anticipated that there would not be many RCTs eligible for inclusion.

DATA COLLECTION AND ANALYSIS

Two review authors working independently selected studies for inclusion in the review, assessed trials for risk of bias, and extracted data. The primary outcome was proportion of participants with complete healing at four to eight weeks. Secondary outcomes included visual acuity, morphology, adverse events, and treatment failure at four to eight weeks.

MAIN RESULTS

We included three trials (two RCTs and one quasi-RCT) in this review for a total of 59 participants (59 eyes) with bacterial keratitis. Trials were all single-center and were conducted in Egypt, Iran, and Thailand between 2010 and 2014. It is very uncertain whether PACK-CXL with standard antibiotic therapy is more effective than standard antibiotic therapy alone for re-epithelialization and complete healing (risk ratio (RR) 1.53, 95% confidence interval (CI) 0.88 to 2.66; participants = 15). We judged the certainty of the evidence to be very low due to the small sample size and high risk of selection and performance bias. The high risk of selection bias reflects the overall review. Masking of participants was not possible for the surgical arm. No participant had a best-corrected visual acuity of 20/100 or better at eight weeks (very low certainty evidence). There is also no evidence that use of PACK-CXL with standard therapy results in fewer instances of treatment failure than standard therapy alone (RR 0.50, 95% CI 0.05 to 4.98; participants = 32). We judged the certainty of evidence to be low due to the small sample size and high risk of selection bias. There were no adverse events reported at 14 days (low certainty evidence). Data on other outcomes, such as visual acuity and morphological characteristics, could not be compared because of variable time points and specific metrics.

AUTHORS' CONCLUSIONS

The current evidence on the effectiveness of PACK-CXL for bacterial keratitis is of low certainty and clinically heterogenous in regard to outcomes. There are five ongoing RCTs enrolling 1136 participants that may provide better answers in the next update of this review. Any future research should include subgroup analyses based on etiology. A core outcomes set would benefit healthcare decision-makers in comparing and understanding study data.

Noninvasive detection of nanoscale structural changes in cornea associated with cross-linking treatment

Corneal cross-linking (CXL) using ultraviolet-A (UVA) irradiation with a riboflavin photosensitizer has grown from an interesting concept to a practical clinical treatment for corneal ectatic diseases globally, such as keratoconus. To characterize the corneal structural changes, existing methods such as X-ray microscopy, transmission electron microscopy, histology and optical coherence tomography (OCT) have been used. However, these methods have various drawbacks such as invasive detection, the impossibility for in vivo measurement, or limited resolution and sensitivity to structural alterations. Here, we report the application of oversampling nanosensitive OCT for probing the corneal structural alterations. The results indicate that the spatial period increases slightly after 30 minutes riboflavin instillation but decreases significantly after 30 minutes UVA irradiation following the Dresden protocol. The proposed noninvasive method can be implemented using existing OCT systems, without any additional components, for detecting nanoscale changes with the potential to assist diagnostic assessment during CXL treatment, and possibly to be a real-time monitoring tool in clinics.

Collagen crosslinking with photoactivated riboflavin in advanced infectious keratitis with corneal melting: Electrophysiological Study

AIM

To assess the effect of photoactivated chromophore for keratitis crosslinking (PACK-CXL) in case of severe keratitis with melting on the electrophysiological function of the retina and the optic nerve.

METHODS

The study included 32 eyes of 32 patients with smear positive severe infectious keratitis with corneal melting. The patients were randomly divided into two groups. Group I (control group) included 16 eyes received systemic and topical antimicrobial drugs guarded by culture and sensitivity test. Group II underwent CXL and then continued their antimicrobial treatment. Full field electroretinogram (ERG) and flash visual evoked potential (VEP) were done for each patient in both groups basically and then 1wk, 1 and 3mo post-treatment to assess the changes in the electrophysiological function of the retina and optic nerve.

RESULTS

Healing of 10 eyes in group I in comparison to 14 eyes in group II was recorded. The mean duration of healing was 36.56±5.21d in group I vs 20.2±4.4d in group II (P<0.005). In group II, ERG showed an insignificant reduction of all parameters of ERG and VEP after CXL. The amplitude of scotopic rod response, oscillatory potential amplitude, flicker amplitude and photopic cone response were insignificantly decreased (P=0.4, 0.8, 0.1, and 0.3 respectively). There were insignificant prolongation of latencies of scotopic rod, oscillatory potential, flicker and photopic cone response (P=0.2, 0.7, 0.5 and 0.1). There was slight delay in latency of VEP without a significant reduction in amplitude.

CONCLUSION

CXL is an effective technique in treatment of severe infectious keratitis with melting as it halts the melting process with acceptable safety on the retinal and optic nerve function.

Rose Bengal Photodynamic Antimicrobial Therapy for Patients With Progressive Infectious Keratitis: A Pilot Clinical Study

PURPOSE

To report clinical outcomes of rose bengal photodynamic antimicrobial therapy (RB-PDAT) as an adjunct treatment for severe, progressive infectious keratitis.

DESIGN

Consecutive interventional case series.

METHODS

Patients with progressive infectious keratitis unresponsive to standard medical therapy underwent RB-PDAT at the Bascom Palmer Eye Institute from January 2016 through March 2018. RB-PDAT was performed by applying a solution of rose bengal (0.1% or 0.2% RB in balanced salt solution) to the de-epithelialized cornea for 30 minutes, followed by irradiation with a 6 mW/cm² custom-made green LED source for 15 minutes (5.4 J/cm²).

RESULTS

The current study included 18 patients (7 male and 11 female) ranging from 17 to 83 years old. Acanthamoeba was the most frequent microbe (10/17; 59%), followed by Fusarium spp. (4/17; 24%), Pseudomonas aeruginosa (2/17; 12%), and Curvularia spp. (1/17; 6%); 1 patient had no confirmed microbiologic diagnosis. Main clinical risk factor for keratitis included contact lens wear (79%). The average area of epithelial defect prior to first RB-PDAT was 32 ± 27 mm² and average stromal depth hyperreflectivity measured with anterior segment optical coherence tomography was 269 ± 75 μm. Successful RB-PDAT (avoidance of therapeutic keratoplasty) was achieved in 72% of the cases, with an average time to clinical resolution (decreased pain and inflammation with re-epithelialization and infiltrate resolution) of 46.9 ± 26.4 days after RB-PDAT. Time of follow-up after RB-PDAT was 13.3 ± 5.7 months.

CONCLUSION

RB-PDAT can be considered as an adjunct therapy for cases of severe, progressive infectious keratitis before performing a therapeutic keratoplasty.

Cellular and molecular assessment of rose bengal photodynamic antimicrobial therapy on keratocytes, corneal endothelium and limbal stem cell niche

Rose Bengal Photodynamic Antimicrobial Therapy (RB-PDAT) is a novel potential treatment for progressive infectious keratitis. The principle behind this therapy is using Rose Bengal as a photosensitizer that can be activated by green light and results in the production of oxygen free radicals which in turn eradicate the microorganism. Given RB-PDAT's mechanism of action and the potential cytotoxic effects, concerns regarding the safety of this technique have arisen. The purpose of this study was to evaluate the effect of RB-PDAT on keratocytes, while focusing on the safety profile that the photo-chemical reaction has on the limbal stem cell (LSC) niche and endothelial cell layer of the treated cornea. To perform RB-PDAT, Rose Bengal solution (0.1% RB in BSS) was applied to the right cornea of rabbits for 30 min and then irradiated by a custom-made green LED light source (525 nm, 6 mW/cm²) for 15 min (5.4 J/cm²). Three rabbits were sacrificed and enucleated after 24 h for evaluation. TUNEL assay and immunohistochemistry for endothelium and limbal stem cell viability were performed on whole mounts and frozen sections in treated and control eyes. LSC of both eyes were isolated and cultured to perform MTT viability and proliferation, and scratch wound healing assays under time-lapse microscopy. Interestingly, while Rose Bengal dye penetration was superficial, yet associated cellular apoptosis was evidenced in up to 1/3 of the stromal thickness on frozen sections. TUNEL assay on whole mounts showed no endothelial cell death following treatment. Immunohistochemistry on frozen sections of LSC displayed no structural difference between treated and non-treated eyes. There was no difference in LSC proliferation rates and scratch wound healing assay demonstrated adequate cell migration from treated and non-treated eyes. The current study suggests that even though penetration of the RB dye has been shown to be limited, oxidative stress produced by RB-PDAT can reach deeper into the corneal stroma. Nevertheless, our results show that performing RB-PDAT is safe on the corneal endothelium and has no effect on LSC viability or function.

Cross-Linking-Assisted Infection Reduction: A Randomized Clinical Trial Evaluating the Effect of Adjuvant Cross-Linking on Outcomes in Fungal Keratitis

PURPOSE

To determine if there is a benefit to adjuvant corneal crosslinking (CXL) and to compare natamycin versus amphotericin B for filamentous fungal keratitis.

DESIGN

Outcome-masked, 2×2 factorial design, randomized controlled clinical trial.

PARTICIPANTS

Consecutive patients presenting with moderate vision loss from a smear-positive fungal ulcer at Aravind Eye Hospital, Madurai, India.

METHODS

Study eyes were randomized to 1 of 4 treatment combinations using an adaptive randomization protocol. The treatment arms included (1) topical natamycin 5% alone, (2) topical natamycin 5% plus CXL, (3) topical amphotericin B 0.15% alone, and (4) topical amphotericin 0.15% plus CXL.

MAIN OUTCOME MEASURES

The primary outcome of the trial was microbiological cure at 24 hours on repeat culture. Secondary outcomes included best spectacle-corrected visual acuity (BSCVA) at 3 weeks and 3 months, percentage of study participants with epithelial healing at 3 days, 3 weeks, and 3 months, infiltrate or scar size at 3 weeks and 3 months, 3-day smear and culture, and adverse events.

RESULTS

Those randomized to CXL regardless of medication (topical natamycin or amphotericin) had 1.32-fold increased odds of 24-hour culture positivity, although this was not statistically significant (95% confidence interval [CI], 0.57-3.06; P = 0.51). We were also unable to find a difference in 24-hour culture positivity between those randomized to amphotericin and those randomized to natamycin when evaluating as a group regardless of whether or not they received CXL (coefficient 1.10; 95% CI, 0.47-2.54; P = 0.84). The BSCVA was approximately 0.22 logarithm of the minimum angle of resolution (logMAR) (2.2 Snellen lines) worse on average at 3 weeks among those receiving CXL regardless of medication (95% CI, -0.04 to 0.40; P = 0.04) and 0.32 logMAR (3.2 Snellen lines) worse visual acuity at 3 months after controlling for baseline visual acuity (95% CI, 0.03-0.54; P = 0.02). There was no difference in infiltrate or scar size, percentage of epithelialized or adverse events when comparing CXL with no CXL or the 2 topical medications.

CONCLUSIONS

There appears to be no benefit of adjuvant CXL in the primary treatment of moderate filamentous fungal ulcers, and it may result in decreased visual acuity.

In Vitro Efficacy of Chlorhexidine and a riboflavin/UVA Combination on Fungal Agents of Keratitis

Purpose: Mycotic keratitis is a global ophthalmological problem because it is difficult to diagnose and treat. The aim of the current study was to evaluate the efficiency of using antifungal agents amphotericin B (AMB), voriconazole (VRC), 0.02% chlorhexidine (CHX), and a combination of riboflavin and UVA treatment against two fungal genera (Aspergillus and Fusarium) responsible for keratitis.Methods: We evaluated antifungal efficiencies of riboflavin/UVA and the antifungal drugs VRC, AMB, and CHX (alone and in combination) against fungal inocula at four concentrations. We recorded colony counts of isolates for Aspergillus terreus, A. flavus, A. fumigatus, Fusarium falciforme, F. proliferatum, and F. solani on Mueller-Hinton agar plates.Results: Fungal suspensions exposed to the following treatment combinations did not allow fungal growth: riboflavin/UVA and VRC, riboflavin/UVA and AMB, riboflavin/UVA and CHX, and CHX alone. We observed a statistically significant reduction (P < .05) in the number of colonies on agar plates when fungal suspensions were treated with riboflavin/UVA, VRC, and AMB only.Conclusions: Riboflavin/UVA treatment in combination with AMB, VRC, and CHX are capable of killing keratitis-inducing fungi (P < .05). The antiseptic CHX exerted a considerable antifungal effect on all strains we examined. Therefore, we recommend CHX as additional therapy against mycotic keratitis, particularly when keratitis is caused by multi-resistant members of Fusarium.

High fluence PACK-CXL as adjuvant treatment for advanced Acanthamoeba keratitis

Purpose

To describe the outcome of adjuvant high fluence photoactivated chromophore for infectious keratitis cross-linking (PACK-CXL) used to treat an advanced form of refractory Acanthamoeba keratitis (AK) diagnosed several months after initial presentation.

Observations

An otherwise healthy 24-year old female presented with a severe unilateral keratitis. The diagnosis eluded clinicians for several months and when finally confirmed as AK, anti-amoebic therapy was instated and only appeared to be effective after addition of high fluence PACK-CXL.

Conclusion and importance

In this case of advanced AK, high fluence PACK-CXL treatment given adjuvant to pharmacologic anti-amoebic therapy resulted in lasting pain relief, re-epithelization and eradication of the Acanthamoeba parasite. Given adjuvant to anti-amoebic pharmacotherapy, high fluence PACK-CXL might be a useful method for treating typically refractory advanced AK.

Acanthamoeba keratitis. Review of literature. Case reports

Acanthamoeba keratitis (АК) is a parasitic infectious condition caused by corneal invasion by free-living amoebae. In 86% of cases, AK affects contact lens wearers. Delayed diagnosis and inadequate treatment of this disease leads to development of a severe form of keratouveitis and corneal perforation. Consequently, this group of diseases is one of the causes of visual disability in working-age population.

Long-term outcomes of riboflavin photodynamic antimicrobial therapy as a treatment for infectious keratitis

Purpose

To report the long-term outcomes of three patients with infectious keratitis treated with riboflavin photodynamic antimicrobial therapy (PDAT).

Observations

Case series reporting three patients with infectious keratitis unresponsive to standard medical treatment who underwent riboflavin photodynamic antimicrobial therapy (PDAT) as an adjunct therapy. One male and two female patients were treated, the median age of presentation was 58 years (range, 29-79 years). The organisms isolated and treated were Pseudomonas aeruginosa, Mycobacterium chenolae, and Curvularia spp. Different risk factors to develop corneal infection ulcers were identified, including corneal abrasion in a contact lens user, history of penetrating keratoplasty with chronic use of topical corticosteroids, and organic trauma. The median follow-up was 47 months (range 37-54 months), and there were no complications secondary to riboflavin PDAT treatment. Two cases underwent optical penetrating keratoplasty after infection was resolved and ocular surface was quiet for at least 3 years.

Conclusions and importance

Riboflavin PDAT can be used as an adjunct treatment in infectious keratitis to strengthen the corneal collagen fibers, delay keratolysis, and allow more time for antimicrobials to work and this way prevent a corneal perforation.

Comparison of corneal collagen cross-linking (PACK-CXL) and voriconazole treatments in experimental fungal keratitis

PURPOSE

To compare the antifungal efficacy of corneal collagen cross-linking with photoactivated riboflavin (PACK-CXL) and voriconazole in experimental Fusarium solani and Candida albicans keratitis models.

METHODS

Sixty-four corneas of 32 New Zealand rabbits were included and divided into two main groups. Intrastromal injection of Fusarium and Candida suspensions was performed, and it was observed that keratitis was formed on the third day. Both groups were randomly separated into the following four groups: control, PACK-CXL, voriconazole and PACK-CXL combined with voriconazole. PACK-CXL was applied using 0.25% riboflavin in an accelerated Dresden protocol (total ultraviolet A dose 5.4 J/cm²). Voriconazole was applied topically as 7x1/day with a dose of 1% (10 mg/ml). Corneal buttons were excised on the tenth day, and microbiological and pathological examinations were performed.

RESULTS

The PACK-CXL and PACK-CXL combined with voriconazole groups each had 100 colony-forming unit (CFU/ml) of reproduced micro-organisms compared with 500 CFU/ml in the voriconazole group and 1500 CFU/ml in the control group (p < 0.001) in the Fusarium keratitis model. The PACK-CXL combined with voriconazole group had 100 CFU/ml, the PACK-CXL group had 150 CFU/ml, and the voriconazole group had 200 CFU/ml of reproduced micro-organisms compared with 4000 CFU/ml in the control group (p < 0.002) in the Candida keratitis model. (p < 0.001). Fewer hyphae and non-specific stromal changes were observed in the pathological cross sections examined in subgroups that used CXL.

CONCLUSION

There was less fungus reproduction and a lower keratitis score for Fusarium solani and Candida albicans in the treatment groups compared to the control groups, especially in groups that used PACK-CXL. These results suggest that it is useful to combine PACK-CXL treatment with medical treatment in the fungal keratitis algorithm at the early stage of the disease.

Understanding the Role of Pro-resolving Lipid Mediators in Infectious Keratitis

Keratitis is a sight-threatening inflammatory condition of the cornea that can be caused by both infectious and non-infectious agents. Physical or chemical trauma are typically related to non-infectious keratitis, which may then become secondarily infected or remain non-infected. Etiology of infectious keratitis is most often associated with bacteria; but viruses, fungi, and parasites are common causative pathogens as well. As a global concern, common risk factors include: systemic immunosuppression (secondary to malnutrition, alcoholism, diabetes, steroid use), previous corneal surgery (refractive corneal surgery, penetrating keratoplasty), extended wear contact lens use, pre-existing ocular surface diseases (dry eye, epithelial defect) and ocular trauma (agriculture- or farm-related) [1-8]. Annual rates of incidence include nearly one million clinical visits due to keratitis in the United States, while it has been reported that roughly two million people develop corneal ulcers in India. Clinically, patients may show signs of eye pain (ranging from mild to severe), blurred vision, photophobia, chemosis and redness. Pathogenesis is generally characterized by rapid progression, focal white infiltrates with underlying stromal inflammation, corneal thinning, stromal edema, mucopurulent discharge and hypopyon, which can lead to corneal scarring, endophthalmitis, and perforation. In fact, corneal opacity is not only a complication of keratitis, but among the leading causes of legal blindness worldwide. Despite that empirical treatment effectively controls most of the pathogens implicated in infectious keratitis, improved clinical outcomes are not guaranteed. Further, if treatment is not initiated in a timely manner, good visual outcome is reduced to approximately 50% of keratitis patients [9]. Moreover, resultant structural alterations, loss of tissue and an unresolved host response remain unaddressed through current clinical management of this condition.

UV light crosslinking regresses mature corneal blood and lymphatic vessels and promotes subsequent high-risk corneal transplant survival

Immunologic graft rejection is the main complication after corneal transplant into pathologically prevascularized so-called high-risk eyes. The aim of this study was to evaluate whether ultraviolet (UV) light crosslinking can regress pathologic corneal blood and lymphatic vessels and thereby improve subsequent graft survival. Using the murine model of suture-induced corneal neovascularization, we found that corneal crosslinking with UVA light and riboflavin regressed both preexisting blood and lymphatic vessels significantly via induction of apoptosis in vascular endothelial cells. In addition, macrophages and CD45⁺ cell counts were significantly reduced. Consistently, corneal crosslinking reduced keratocyte density and corneal thickness without affecting corneal nonvascular endothelial cells, iris, and lens depending on the crosslinking duration. Furthermore, using the murine model of corneal transplant, long-term graft survival was significantly promoted (P < .05) and CD4⁺ CD25⁺ FoxP3⁺ T regulatory cells were upregulated (P < .01) in high-risk eyes preoperatively treated with crosslinking. Our results suggest UV light crosslinking as a novel method to regress both pathologic corneal blood and lymphatic vessels and to reduce CD45⁺ inflammatory cells. Furthermore, this study demonstrates for the first time that preoperative corneal crosslinking in prevascularized high-risk eyes can significantly improve subsequent graft survival and may become a promising novel therapy in the clinic.

Impact of Iontophoresis and PACK-CXL Corneal Concentrations of Antifungals in an In Vivo Model

PURPOSE

To investigate voriconazole (VRZ) penetration and fungal load in the cornea after applying VRZ therapy with various treatment combinations in a fungal keratitis model.

METHODS

Fifty-four eyes of 27 young albino rabbits were provided for this experimental study. Twelve corneas were inoculated with Candida albicans, 12 corneas were inoculated with Fusarium solani, and 6 eyes were selected as controls. Infected corneas received various treatment combinations including VRZ 1% drop therapy alone, VRZ 1% plus amphotericin B 1% drop combination therapy, iontophoretic VRZ therapy, and VRZ 1% drop therapy after corneal cross-linking. Fungal load was measured by log reduction, and VRZ levels were quantified by liquid chromatography-tandem mass spectrometry.

RESULTS

Iontophoresis-assisted VRZ application showed the highest antifungal activity against F. solani keratitis (4-log reduction) and C. albicans keratitis (5-log reduction) compared with other treatment applications. VRZ levels were also found to be the highest in corneas that received iontophoretic VRZ treatment (3.6313 ± 0.0990 ppb for F.solani keratitis and 1.7001 ± 0.0065 ppb for C. albicans keratitis) compared with other treatment applications.

CONCLUSIONS

Iontophoresis seems to provide the highest VRZ concentration and highest antifungal activity in the cornea compared with other treatment applications for C. albicans and F. solani keratitis.

Changes in interleukin-6 tear concentration and clinical outcome in moderate-to-severe bacterial corneal ulcers after corneal collagen cross-linking

We aimed to evaluate interleukin-6 (IL-6) tear concentration and clinical outcome in patients with moderate-to-severe bacterial corneal ulcers post corneal collagen cross-linking (CXL) therapy. This pre-post designed study involving 21 moderate-to-severe corneal ulcer patients who underwent CXL therapy. Patients with infectious corneal ulcer were given CXL therapy as adjunctive treatment after 5d of broadspectrum antibiotic treatment. Patients with moderate to severe infectious bacterial corneal ulcers were included in this study. Tear sampling was performed before CXL therapy, using sterile Schimer paper from conjunctival inferior fornix. CXL therapy was performed in accordance with the CXL Dresden protocol. Data recording and tear sampling were then performed at day 1 and day 7 after CXL therapy. Data recording included, presence of conjunctival hyperemia, visual analogue scale (VAS), size of corneal defects, and decemetocele. There was a decrease in IL-6 tear concentration by day 7 after CXL therapy (P=0.001). IL-6 concentration at 1h after therapy (2274.67±2120.46 pg/mL) tended to be lower than before therapy (4330.09±3169.70 pg/mL), but the difference was not statistically significant (P=0.821). The size of corneal defects decreased significantly post CXL (P=0.007). The logMAR visual acuity before and after CXL therapy was not found to be significantly different (P=0.277). There was a significant decrease in VAS values (P=0.018) and blepharospasm (P=0.011) pre and post CXL. There was no significant decrease in conjunctival hyperemia pre and post CXL (P=0.293). There was significant reduction in IL-6 tear concentration and clinical improvement in moderate-to-severe bacterial corneal ulcers which underwent CXL therapy.

Antimicrobial Studies Using the Therapeutic Tissue Cross-Linking Agent, Sodium Hydroxymethylglycinate: Implication for Treating Infectious Keratitis

Purpose

Our recent studies raise the possibility of using sodium hydroxymethylglycinate (SMG), for pharmacologic therapeutic tissue cross-linking (TXL) of the cornea. The present study was performed to evaluate the antimicrobial effects of SMG for potential use in treating infectious keratitis.

Methods

In initial (group 1) experiments, methicillin-sensitive Staphylococcus aureus (MSSA), methicillin-resistant Staphylococcus aureus (MRSA), and Pseudomonas aeruginosa (PA) were treated with SMG (10–40 mM) for 10 to 120 minutes. In group 2 experiments, MRSA, PA, Candida albicans (CA), and vancomycin-resistant Enterococcus (VRE) were treated with SMG (20–200 mM) for 30 minutes. In group 2 experiments, BSA and neutralizing buffer were added to provide a proteinaceous medium, and to ensure precise control of SMG exposure times, respectively. SMG effectiveness was quantitated based on pathogen growth following a 24- to 48-hour incubation period.

Results

In group 1 experiments, as expected, time- and concentration-dependent bactericidal effects were noted using MSSA. In addition, the effect of SMG (40 mM) was greatest against MSSA (99.3%), MRSA (96.0%), and PA (97.4%) following a 2-hour exposure with lesser effects following 30- and 10-minute exposures. In group 2 experiments, concentration-dependent bactericidal effects were confirmed for MRSA (91%), PA (99%), and VRE (55%) for 200-mM SMG with 30-minute treatment. SMG was not as effective against CA, with a maximum kill rate of 37% at 80 mM SMG.

Conclusions

SMG solution exhibits a dose-dependent bactericidal effect on MSSA, MRSA, and PA, with milder effects on VRE and CA. These studies raise the possibility of using SMG TXL for the treatment of infectious keratitis.

The Significance of Repeat Cultures in the Treatment of Severe Fungal Keratitis

PURPOSE

To identify fungal keratitis patients who are at risk of a poor outcome and may benefit from closer follow-up or more aggressive treatment.

DESIGN

Secondary analysis of randomized clinical trial data.

METHODS

We compared the clinical outcomes of patients who had positive 6-day fungal cultures with those who did not, using backward stepwise regression with covariates for all baseline clinical characteristics.

SUBJECTS

Patients presenting with a smear-positive filamentous fungal ulcer and visual acuity of 20/400 or worse, and who subsequently had a 6-day fungal culture performed at the Aravind Eye Care system (India), Lumbini Eye Hospital (Nepal), or Bharatpur Eye Hospital (Nepal).

MAIN OUTCOME MEASURES

The primary outcome is rate of corneal perforation and/or the need for therapeutic penetrating keratoplasty. Secondary outcomes include 3-month best spectacle-corrected visual acuity (BSCVA), 3-month infiltrate and/or scar size, and rate of re-epithelialization.

RESULTS

Patients who tested positive at their 6-day culture had twice the hazard of experiencing a corneal perforation or the need for therapeutic penetrating keratoplasty (P = .002) than those who tested negative, even after controlling for baseline ulcer characteristics. These patients also had on average 0.26 logMAR lines worse BSCVA at 3 months (P = .001). Culture positivity at day 6 was not a statistically significant predictor of 3-month infiltrate/scar-size (-0.24 mm¹; P = .45) or time to re-epithelialization (hazard ratio = .81; P = .31).

CONCLUSIONS

Here we identify a uniquely valuable clinical tool, day 6 culture results, for the treatment of severe fungal keratitis. Risk stratification based on repeat culture positivity is an objective way to assess response to medical therapy and identify patients who are at high risk of a poor clinical outcome. This establishes a new standard of care for severe fungal keratitis management.

[Corneal collagen cross-linking in the treatment of infectious keratitis and corneal ulcers]

In recent years, collagen cross-linking (CXL) of the cornea has acquired a new usage - in the treatment of infectious keratitis and corneal ulcers. This review was aimed at compiling the previously published data and assessing the effectiveness of the method.

Expert practice patterns and opinions on corneal cross-linking for infectious keratitis

Objective

To assess the current opinion and practice patterns from cornea experts regarding the benefit of corneal cross-linking (CXL) for infectious keratitis (IK).

Methods and analysis

An international survey was distributed to corneal specialists via an internet survey. The survey data collected were analysed with descriptive statistics.

Results

A survey was sent to 190 recipients, and 29 (15%) respondents completed the survey with an average of 7 years’ experience using CXL. A majority of respondents (66%) used CXL to treat IK due to bacterial, fungal, protozoan or unknown aetiology. Main indications to use CXL as adjuvant therapy were worsening infiltrate diameter or depth despite therapy (74%), followed by antibiotic resistance (68%), corneal thinning (53%), poor compliance with medication (26%) and other reasons (21%). Most respondents felt CXL would be at least moderately helpful as an adjuvant therapy for bacterial (96%) or fungal (75%) keratitis; about half (46%) thought it would be helpful for acanthamoeba keratitis. As sole therapy, fewer respondents believed CXL would be at least moderately helpful to treat bacterial (75%), fungal (58%) and acanthamoeba (43%) keratitis.

Conclusion

The survey offered insights into current expert practices and opinions of using CXL as therapy for IK. The results of this survey serve to guide in the design of future clinical studies.

Corneal Collagen Cross-Linking for the Management of Mycotic Keratitis

PURPOSE

To evaluate the efficiency of corneal collagen cross-linking (CXL) in addition to topical voriconazole in cases with mycotic keratitis.

DESIGN

Retrospective case series in a tertiary university hospital.

PARTICIPANTS

CXL was performed on 13 patients with mycotic keratitis who presented poor or no response to topical voriconazole treatment.

METHODS

The clinical features, symptoms, treatment results and complications were recorded retrospectively. The corneal infection was graded according to the depth of infection into the stroma (from grade 1 to grade 3). The visual analogue scale was used to calculate the pain score before and 2 days after surgery.

MAIN OUTCOME MEASURES

Grade of the corneal infection.

RESULTS

Mean age of 13 patients (6 female and 7 male) was 42.4 ± 17.7 years (20-74 years). Fungus was demonstrated in culture (eight patients) or cytological examination (five patients). Seven of the 13 patients (54%) were healed with topical voriconazole and CXL adjuvant treatment in 26 ± 10 days (15-40 days). The remaining six patients did not respond to CXL treatment; they initially presented with higher grade ulcers. Pre- and post-operative pain score values were 8 ± 0.8 and 3.5 ± 1, respectively (p < 0.05).

CONCLUSIONS

The current study suggests that adjunctive CXL treatment is effective in patients with small and superficial mycotic ulcers. These observations require further research by large randomized clinical trials.

Bilateral Mycobacterium chelonae Keratitis after Phacoemulsification Cataract Surgery

The purpose of this manuscript is to report the case of an 81-year-old patient who presented with bilateral keratitis after phacoemulsification surgery. Cultures came back positive for Mycobacterium chelonae. Despite aggressive topical and systemic antimicrobial treatment, the patient developed a corneal perforation in both eyes, treated with corneal glue in the right eye and corneoscleral patch in the left eye. After two years of follow-up, patient was free of infection in the right eye with visual acuity of 20/200 and the left eye progressed to phthisis bulbi. We present an unusual case of bilateral Mycobacterium chelonae keratitis associated with phacoemulsification cataract surgery. This case represents the importance of making clinicians aware of this devastating infection and highlights the need for better management to improve outcomes.

Update on the Management of Infectious Keratitis

Infectious keratitis is a major global cause of visual impairment and blindness, often affecting marginalized populations. Proper diagnosis of the causative organism is critical, and although culture remains the prevailing diagnostic tool, newer techniques such as in vivo confocal microscopy are helpful for diagnosing fungus and Acanthamoeba. Next-generation sequencing holds the potential for early and accurate diagnosis even for organisms that are difficult to culture by conventional methods. Topical antibiotics remain the best treatment for bacterial keratitis, and a recent review found all commonly prescribed topical antibiotics to be equally effective. However, outcomes remain poor secondary to corneal melting, scarring, and perforation. Adjuvant therapies aimed at reducing the immune response associated with keratitis include topical corticosteroids. The large, randomized, controlled Steroids for Corneal Ulcers Trial found that although steroids provided no significant improvement overall, they did seem beneficial for ulcers that were central, deep or large, non-Nocardia, or classically invasive Pseudomonas aeruginosa; for patients with low baseline vision; and when started early after the initiation of antibiotics. Fungal ulcers often have worse clinical outcomes than bacterial ulcers, with no new treatments since the 1960s when topical natamycin was introduced. The randomized controlled Mycotic Ulcer Treatment Trial (MUTT) I showed a benefit of topical natamycin over topical voriconazole for fungal ulcers, particularly among those caused by Fusarium. MUTT II showed that oral voriconazole did not improve outcomes overall, although there may have been some effect among Fusarium ulcers. Given an increase in nonserious adverse events, the authors concluded that they could not recommend oral voriconazole. Viral keratitis differs from bacterial and fungal cases in that it is often recurrent and is common in developed countries. The Herpetic Eye Disease Study (HEDS) I showed a significant benefit of topical corticosteroids and oral acyclovir for stromal keratitis. HEDS II showed that oral acyclovir decreased the recurrence of any type of herpes simplex virus keratitis by approximately half. Future strategies to reduce the morbidity associated with infectious keratitis are likely to be multidimensional, with adjuvant therapies aimed at modifying the immune response to infection holding the greatest potential to improve clinical outcomes.

Comparison between corneal cross-linking, topical antibiotic and combined therapy in experimental bacterial keratitis model

Purpose

This study was conducted to investigate the effects of an experimental bacterial keratitis model on the corneal collagen cross-linking treatment (CXL), and also to compare topical antibiotic treatment with the combined treatment.

Methods

The study involved 40 young adult female Sprague Dawley rats, which had a 2 mm scraped defect of the central corneal epithelium in both eyes. The rats were divided into two equal groups. The first group was inoculated in both eyes with standard Pseudomonas Aeruginosa (PA) from a strain suspension prepared from 0.05 ml (Group 1), and the second group was inoculated with standard Methicillin Resistance Staphylococcus Aureus (MRSA) strains from a suspension prepared from 0.05 ml (Group 2). Group 1 was divided into four sub-groups: Group 1A was treated by collagen cross-linking (CXL), Group 1C was treated with topical tobramycin drops CXL and also treated by collagen cross-linking (CXL), Group 1D was treated with topical tobramycin drops, and Group 1B was left untreated in order to create a control group. Similarly, Group 2 was also divided into four sub-groups: Group 2A was treated by CXL, Group 2C was treated with topical 5% fortified vancomycin drops CXL and also treated by CXL, Group 2D was treated with topical 5% fortified vancomycin drops, and Group 2B was left untreated in order to create a control group. CXL was performed on the third day following the inoculation and topical drop therapy. Biomicroscopy and microbiologic assessments were performed on the third and seventh days following the inoculation of microorganisms.

Results

In the treatment, which compared baselines in all groups before treatment, the diameter of keratitis infiltrations, corneal clouding, and corneal swab samples were obtained from the reduction in reproduction. The results were statistically significant (p < 0.01). Keratitis infiltration groups were conducted on the seventh day for Groups 1C and 1D according to Group 1B, whilst Groups 2A, 2C and 2D were conducted according to Group 2B, which showed a significant statistical reduction (p < 0.01). On the seventh day, focal groups were conducted in corneal clouding Group 1D according to Group 1B and in Groups 2A, 2C and 2D according to Group 2B, which revealed a significant statistical reduction (p < 0.01). On the seventh day, reproduction in culture was obtained from corneal swab samples in Groups 1C and 1D according to Group 1B; in Groups 1C and 1D according to Group 1A; in Groups 2A, 2C and 2D according to Group 2B; and in Group 2C according to Group 2A, where a significant statistical reduction was observed (p < 0.01).

Conclusions

The clinical and microbiological efficacy of the CXL treatment is evaluated in our study. In accordance with the conclusion reached an effective reduction in the density and severity of (infection), occurred as a result of CXL treatment, CXL treatment combined with topical antibiotic treatment and topical antibiotic treatment of Pseudomonas Aeruginosa (PA) and Metisilin Rezistant Staphylococcus Aureus (MRSA) keratitis infections. From these results, it is shown that topical antibiotics and CXL potentiate each other’s effects in the treatment of resistant bacterial keratitis.

Corneal Cross-Linking Has No Effect on Matrix Metalloproteinase 9 and 13 Levels During Fungal Keratitis on the Early Stage

The aim of our study was to investigate matrix metalloproteinases, MMP-9 and MMP-13 levels, in the rabbit model of Fusarium and Candida keratitis treated by corneal cross-linking (PACK-CXL). Rabbit corneas were inoculated with fungal inoculum for keratitis. Each group divided into four subgroups, including un-treated group, PACK-CXL group, voriconazole group and PACK-CXL plus voriconazole group. PACK-CXL was applied with 0.25% riboflavin in accelerated Dresden protocol, and 0.1% voriconazole drops were administered. All corneal buttons excised at tenth day after ophthalmological examination. Fungal cell counts and Scheiber scores were determined in all groups. Corneal tissue MMP mRNA levels were evaluated quantitative reverse transcriptase PCR. The difference in MMP-9 and MMP-13 levels at all groups was not statistically significant (p > 0.05). PACK-CXL with 0.25% riboflavin either alone or combined with antifungal drops was unable to provide decline in inflammatory findings in both macroscopic and microscopic levels similar to medical antifungal treatment.

Bilateral corneal perforation due to MRSA keratitis in a crosslinking patient

Introduction: The cornea may become infected and perforated after epithelium-on collagen crosslinking. Case presentation: A healthy 33-year-old male who underwent corneal collagen crosslinking in both eyes developed a purulent keratitis and bilateral corneal perforations, requiring bilateral penetrating keratoplasties. He was exposed to methicillin resistant staphylococcus aureus (MRSA) by a family member with a tracheostomy and was treated with MRSA-directed antibiotics. After prolonged recovery and treatment of his infection, he had acceptable but limited uncorrected visual acuity, with excellent corrected visual acuity. Conclusion: While epithelium-on crosslinking is commonly thought to be associated with a lower risk of postoperative infection, this case illustrates that even epithelium-on treatment may present the patient with a risk of infection. Patients in higher risk groups who are exposed to infectious disease may be more predisposed.