Mycotic keratitis: susceptibility to antiseptic agents

Local Ugandan Production of Stable 0.2% Chlorhexidine Eye Drops

Purpose

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

Methods

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

Results

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

Conclusions

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

Translational Relevance

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

Management of Filamentous Fungal Keratitis: A Pragmatic Approach

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

Topical Chlorhexidine 0.2% versus Topical Natamycin 5% for the Treatment of Fungal Keratitis in Nepal: A Randomized Controlled Noninferiority Trial

PURPOSE

To investigate if topical chlorhexidine 0.2%, which is low cost and easy to formulate, is noninferior to topical natamycin 5% for the treatment of filamentous fungal keratitis.

DESIGN

Randomized controlled, single-masked, noninferiority clinical trial.

PARTICIPANTS

Adults attending a tertiary-level ophthalmic hospital in Nepal with filamentous fungal infection confirmed on smear or confocal microscopy.

METHODS

Participants were randomly allocated to receive topical chlorhexidine 0.2% or topical natamycin 5%. Primary analysis (intention-to-treat) was by linear regression, using baseline logarithm of the minimum angle of resolution (logMAR) best spectacle-corrected visual acuity (BSCVA) and treatment arm as prespecified covariates. Mixed fungal-bacterial infections were excluded from the primary analysis but included in secondary analyses and secondary safety-related outcomes. The noninferiority margin was 0.15 logMAR. This trial was registered with ISRCTN, number ISRCTN14332621.

MAIN OUTCOME MEASURES

The primary outcome measure was BSCVA at 3 months. Secondary outcome measures included perforation or therapeutic penetrating keratoplasty by 90 days.

RESULTS

Between June 3, 2019, and November 9, 2020, 354 eligible participants were enrolled and randomly assigned: 178 to chlorhexidine and 176 to natamycin. Primary outcome data were available for 153 and 151 of the chlorhexidine and natamycin groups, respectively. Of these, mixed bacterial-fungal infections were found in 20 cases (12/153 chlorhexidine, 8/151 natamycin) and excluded from the primary analysis. Therefore, 284 patients were assessed for the primary outcome (141 chlorhexidine, 143 natamycin). We did not find evidence to suggest chlorhexidine was noninferior to natamycin and in fact found strong evidence to suggest that natamycin-treated participants had significantly better 3-month BSCVA than chlorhexidine-treated participants, after adjusting for baseline BSCVA (regression coefficient, -0.30; 95% confidence interval [CI], -0.42 to -0.18; P < 0.001). There were more perforations and emergency corneal grafts in the chlorhexidine arm (24/175, 13.7%) than in the natamycin arm (10/173, 5.8%; P = 0.018, mixed infections included), whereas natamycin-treated cases were less likely to perforate or require an emergency corneal graft, after adjusting for baseline ulcer depth (odds ratio, 0.34; 95% CI, 0.15-0.79; P = 0.013).

CONCLUSIONS

Treatment with natamycin is associated with significantly better visual acuity, with fewer adverse events, compared with treatment with chlorhexidine. Natamycin remains the preferred first-line monotherapy treatment for filamentous fungal keratitis.

Fusarium Keratitis-Review of Current Treatment Possibilities

In many parts of the world, fungi are the predominant cause of infectious keratitis; among which, Fusarium is the most commonly isolated pathogen. The clinical management of this ophthalmic emergency is challenging. Due to the retardation of the first symptoms from an injury and the inability to differentiate fungal from bacterial infections based on clinical symptoms and difficult microbial diagnostics, proper treatment, in many cases, is postponed. Moreover, therapeutical options of Fusarium keratitis remain limited. This paper summarizes the available treatment modalities of Fusarium keratitis, including antifungals and their routes of administration, antiseptics, and surgical interventions.

Fungal keratitis: Mechanisms of infection and management strategies

Fungal corneal ulcers are an uncommon, yet challenging, cause of vision loss. In the United States, geographic location appears to dictate not only the incidence of fungal ulcers, but also the fungal genera most encountered. These patterns of infection can be linked to environmental factors and individual characteristics of fungal organisms. Successful management of fungal ulcers is dependent on an early diagnosis. New diagnostic modalities like confocal microscopy and polymerase chain reaction are being increasingly used to detect and identify infectious organisms. Several novel therapies, including crosslinking and light therapy, are currently being tested as alternatives to conventional antifungal medications. We explore the biology of Candida, Fusarium, and Aspergillus, the three most common genera of fungi causing corneal ulcers in the United States and discuss current treatment regimens for the management of fungal keratitis.

Mycotic Keratitis-A Global Threat from the Filamentous Fungi

Mycotic or fungal keratitis (FK) is a sight-threatening disease, caused by infection of the cornea by filamentous fungi or yeasts. In tropical, low and middle-income countries, it accounts for the majority of cases of microbial keratitis (MK). Filamentous fungi, in particular Fusarium spp., the aspergilli and dematiaceous fungi, are responsible for the greatest burden of disease. The predominant risk factor for filamentous fungal keratitis is trauma, typically with organic, plant-based material. In developed countries, contact lens wear and related products are frequently implicated as risk factors, and have been linked to global outbreaks of Fusarium keratitis in the recent past. In 2020, the incidence of FK was estimated to be over 1 million cases per year, and there is significant geographical variation; accounting for less than 1% of cases of MK in some European countries to over 80% in parts of south and south-east Asia. The proportion of MK cases is inversely correlated to distance from the equator and there is emerging evidence that the incidence of FK may be increasing. Diagnosing FK is challenging; accurate diagnosis relies on reliable microscopy and culture, aided by adjunctive tools such as in vivo confocal microscopy or PCR. Unfortunately, these facilities are infrequently available in areas most in need. Current topical antifungals are not very effective; infections can progress despite prompt treatment. Antifungal drops are often unavailable. When available, natamycin is usually first-line treatment. However, infections may progress to perforation in ~25% of cases. Future work needs to be directed at addressing these challenges and unmet needs. This review discusses the epidemiology, clinical features, diagnosis, management and aetiology of FK.

Chlorhexidine for the Treatment of Fusarium Keratitis: A Case Series and Mini Review

Fungal keratitis is difficult to treat, especially Fusarium keratitis. In vitro studies show that chlorhexidine could be an interesting option as monotherapy. We describe a case series of four patients (four eyes) with Fusarium keratitis at Radboud University Medical Center (Nijmegen, the Netherlands). The patients were treated with chlorhexidine 0.02% eye drops. The in vitro activity of eight antifungals and chlorhexidine was determined according to the European Committee on Antimicrobial Susceptibility Testing (EUCAST) broth microdilution method. We also reviewed the literature on the use of chlorhexidine in the treatment of fungal keratitis. Topical chlorhexidine was well tolerated, and all patients showed complete resolution of the keratitis upon treatment with chlorhexidine. A PubMed search of the available literature was conducted (last search 8 March 2020) and yielded two randomized clinical trials (natamycin versus chlorhexidine) and one case report addressing the treatment of fungal keratitis with chlorhexidine. Chlorhexidine was found to be safe with regard to toxicity and to be superior to natamycin in the clinical trials. Chlorhexidine showed in vitro fungicidal activity against Fusarium and clinical effectiveness in our cases, supporting further clinical evaluation. Advantages of chlorhexidine are its topical application, its general availability, its low costs, its broad-spectrum activity, and its fungicidal mechanism of action at low concentrations.

Topical chlorhexidine 0.2% versus topical natamycin 5% for fungal keratitis in Nepal: rationale and design of a randomised controlled non-inferiority trial

INTRODUCTION

Fungal infections of the cornea, fungal keratitis (FK), are challenging to treat. Current topical antifungals are not always effective and are often unavailable, particularly in low-income and middle-income countries where most cases occur. Topical natamycin 5% is usually first-line treatment, however, even when treated intensively, infections may progress to perforation of the eye in around a quarter of cases. Alternative antifungal medications are needed to treat this blinding disease.Chlorhexidine is an antiseptic agent with antibacterial and antifungal properties. Previous pilot studies suggest that topical chlorhexidine 0.2% compares favourably with topical natamycin. Full-scale randomised controlled trials (RCTs) of topical chlorhexidine 0.2% are warranted to answer this question definitively.

METHODS AND ANALYSIS

We will test the hypothesis that topical chlorhexidine 0.2% is non-inferior to topical natamycin 5% in a two-arm, single-masked RCT. Participants are adults with FK presenting to a tertiary ophthalmic hospital in Nepal. Baseline assessment includes history, examination, photography, in vivo confocal microscopy and cornea scrapes for microbiology. Participants will be randomised to alternative topical antifungal treatments (topical chlorhexidine 0.2% and topical natamycin 5%; 1:1 ratio, 2-6 random block size). Patients are reviewed at day 2, day 7 (with reculture), day 14, day 21, month 2 and month 3. The primary outcome is the best spectacle corrected visual acuity (BSCVA) at 3 months. Primary analysis (intention to treat) will be by linear regression, with treatment arm and baseline BSCVA prespecified covariates. Secondary outcomes include epithelial healing time, scar/infiltrate size, ulcer depth, hypopyon size, perforation and/or therapeutic penetrating keratoplasty (corneal transplant), positive reculture rate (day 7) and quality of life (EuroQol-5 dimensions, WHO/PBD-VF20, WHOQOL-BREF).

ETHICS AND DISSEMINATION

The Nepal Health Research Council, the Nepal Department of Drug Administration and the London School of Hygiene and Tropical Medicine ethics committee have approved the trial. The results will be presented at local and international meetings and submitted to peer-reviewed journals for publication.

TRIAL REGISTRATION NUMBER

ISRCTN14332621; pre-results.

A Novel Vitamin E TPGS-Based Formulation Enhances Chlorhexidine Bioavailability in Corneal Layers

Keratitis is a severe condition characterized by inflammation of the cornea following a local trauma. The most common ocular disease is the bacterial one, which requires an antibiotic treatment. The major limitation of this therapy is the resistance of the antibiotic. For this reason, alternative procedures have been developed and consist of antimicrobial molecules. One of the most used is the chlorhexidine gluconate, which has shown activity versus Gram-positive and Gram-negative bacteria and fungi. In addition to its efficiency, chlorhexidine shows low toxicity levels for mammalian cells and is a low-cost molecule. Despite its multiple benefits, chlorhexidine, if used at concentrations higher than 0.02% (w/w), can cause local eye irritation. Additionally, its poor penetrability through the cornea makes necessary frequent instillation of eye drops for a prolonged time. Due to these limitations, alternative drug delivery strategies are required. Here, we report a novel formulation based on the combination of d-alpha-tocopherol polyethylene glycol 1000 succinate with chlorhexidine, which results in higher accumulation of the drug in human corneas measured by liquid chromatography and strong antimicrobial activity. Moreover, this formulation does not cause any toxic effect on human cells and is well tolerated by rabbit eyes. Therefore this novel formulation represents a good candidate for the treatment of keratitis that overcomes the risk of antibiotic resistance.

In Vitro Topical Delivery of Chlorhexidine to the Cornea: Enhancement Using Drug-Loaded Contact Lenses and β-Cyclodextrin Complexation, and the Importance of Simulating Tear Irrigation

Microbial keratitis is a severe, sight-threatening condition caused by various pathogens. Eyedrops are the standard delivery modality for treating these disorders; however, blinking reflex, elevated tear production, and nasolacrimal drainage eliminate much of the instilled dose within a few seconds. Therefore, eyedrops must be applied repeatedly for prolonged periods. The present study aimed to probe more effective ocular delivery of chlorhexidine based upon drug-loaded hydrogel contact lenses and β-cyclodextrin (β-CD), while also determining the effect of constant irrigation with simulated tear fluid (STF) in in vitro experiments. Chlorhexidine digluconate (as 0.2 and 2% solutions, β-CD inclusion complexes, and loaded hydrogel contact lenses) were applied to enucleated porcine eyes as single or multiple 10 μL doses, or as drug-loaded contact lenses, with and without β-CD. The corneas were then excised and drug-extracted quantified by high-performance liquid chromatography (HPLC). The effect of constant irrigation by STF was evaluated to test the effect of increased tear production on corneal delivery. Potential antimicrobial activity of the delivered drug was also assessed. Results showed that drug-loaded contact lenses delivered the greatest amount of chlorhexidine into the cornea over a 24 h period, while the eyedrop solution comparator delivered the least. The β-CD significantly enhanced chlorhexidine delivery to the cornea from eyedrop solution, although contact lenses loaded with chlorhexidine-β-CD failed to enhance delivery. β-CD within the hydrogel matrix impeded drug release. Constant irrigation with STF significantly reduced the amount of drug delivered to the cornea in all cases. Chlorhexidine retained antimicrobial activity in all delivery methods. Hydrogel contact lenses loaded with chlorhexidine delivered significantly higher levels to the cornea compared to eyedrops, either multiple hourly doses or a single dose. They also offer reduced application, in particular, to a nonulcerated corneal infection. Finally, the importance of fully accounting for tear production in in vitro ocular delivery experiments was highlighted.

Boston Type I Keratoprosthesis: Antibacterial Resistance and Microbiota Evaluation of Soft Contact Lenses

PURPOSE

To evaluate microbiota colonizing soft contact lenses (CL) in eyes with Boston type I keratoprosthesis (BKPro), and determine the prevalence of resistance to fourth-generation fluoroquinolone (FQ).

DESIGN

Prospective, observational study.

SUBJECTS

Patients with BKPro using CL as routine who were in postoperative follow-up in the Department of Ophthalmology of the Federal University of Sao Paulo, and volunteered to participate in the study. All patients were under a prophylactic scheme of topical 0.5% moxifloxacin 3 times a day and topical 5% povidone-iodine (PI) at the time of CL exchange.

METHODS

Patients on scheduled replacement scheme of CL had their lenses removed and sent for microbiological analysis. Standard culture methods were used for microorganism identification and susceptibility to different antibiotics was tested. Main outcome measure was prevalence of resistance to fourth-generation FQ.

RESULTS

Among the 19 eyes, 12 eyes (63%) had at least 1 positive bacterial culture. The most prevalent isolates were Staphylococcus epidermidis and other coagulase-negative staphylococci. Actinomyces viscosus was isolated in 1 CL. Fungal cultures were all negative. Of the 12 eyes with culture bacterial growth, resistance to fourth-generation FQ (0.5% moxifloxacin) was identified in 6 different eyes (50%). None presented infectious complications.

CONCLUSIONS

FQ-resistant bacteria were isolated in some patients. Although our prophylactic antibiotic regimen has been efficient in preventing bacterial infection, this analysis demonstrated that prophylaxis with PI and low FQ dose might increase resistance to antibiotics. Investigations in this field may help to outline future changes of prophylactic guidelines and therapeutic strategies.

Surgical management of refractory nasal aspergillosis using iodine cadexomer dressings in three dogs

BACKGROUND

This case series describes surgical management of nasal aspergillosis refractory to conventional medical management or with evidence of cribriform plate osteolysis in three dogs.

METHODS

All dogs had surgical debridement of mucosa, nasal turbinates and necrotic debris via dorsal sinusotomy/rhinotomy. Sinuses were packed with iodine cadexomer-impregnated bandages for several weeks and affixed with tie-over bandages. Bandage changes were performed under sedation in 2/3 cases. Once mature granulation tissue covered all exposed bone, the tie-over bandages were removed and the sinusotomy/rhinotomy closed by apposing the skin edges.

CONCLUSION

This technique was well tolerated, effective and afforded a cure in all three patients. It should be considered in cases of cribriform lysis or lack of clinical response to conventional medical management.

Medical interventions for fungal keratitis

BACKGROUND

Fungal keratitis is a fungal infection of the cornea. It is common in lower income countries, particularly in agricultural areas but relatively uncommon in higher income countries. Although there are medications available, their effectiveness is unclear.

OBJECTIVES

To assess the effects of different antifungal drugs in the management of fungal keratitis.

SEARCH METHODS

We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (2015, Issue 2), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to March 2015), EMBASE (January 1980 to March 2015), Latin American and Caribbean Health Sciences Literature Database (LILACS) (January 1982 to March 2015), the ISRCTN registry (www.isrctn.com/editAdvancedSearch), ClinicalTrials.gov (www.clinicaltrials.gov) and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 16 March 2015.

SELECTION CRITERIA

We included randomised controlled trials of medical therapy for fungal keratitis.

DATA COLLECTION AND ANALYSIS

Two review authors selected studies for inclusion in the review, assessed trials for risk of bias and extracted data. The primary outcome was clinical cure at two to three months. Secondary outcomes included best-corrected visual acuity, time to clinical cure, compliance with treatment, adverse outcomes and quality of life.

MAIN RESULTS

We included 12 trials in this review; 10 trials were conducted in India, one in Bangladesh and one in Egypt. Seven of these trials were at high risk of bias in one or more domains, two of these studies were at low risk of bias in all domains. Participants were randomised to the following comparisons: topical 5% natamycin compared to topical 1% voriconazole; topical 5% natamycin compared to topical 2% econazole; topical 5% natamycin compared to topical chlorhexidine gluconate (0.05%, 0.1% and 0.2%); topical 1% voriconazole compared to intrastromal voriconazole 50 g/0.1 mL (both treatments combined with topical 5% natamycin); topical 1% voriconazole combined with oral voriconazole compared to both oral voriconazole and oral itraconazole (both combined with topical 5% natamycin); topical 1% itraconazole compared to topical 1% itraconazole combined with oral itraconazole; topical amphotericin B compared to topical amphotericin B combined with subconjunctival injection of fluconazole; intracameral injection of amphotericin B with conventional treatment compared to conventional treatment alone (severe fungal ulcers); topical 0.5% and 1% silver sulphadiazine compared to topical 1% miconazole. Overall the results were inconclusive because for most comparisons only one small trial was available. The exception was the comparison of topical natamycin and topical voriconazole for which three trials were available. In one of these trials clinical cure (healed ulcer) was reported in all 15 people allocated to natamycin and in 14/15 people allocated to voriconazole (risk ratio (RR) 1.07; 95% confidence interval (CI) 0.89 to 1.28, low quality evidence). In one trial people randomised to natamycin were more likely to have a microbiological cure at six days (RR 1.64; 95% CI 1.38 to 1.94, 299 participants). On average, people randomised to natamycin had better spectacle-corrected visual acuity at two to three months compared to people randomised to voriconazole but the estimate was uncertain and the 95% confidence intervals included 0 (no difference) (mean difference -0.12 logMAR, 95% CI -0.31 to 0.06, 434 participants; 3 studies, low quality evidence) and a decreased risk of corneal perforation or therapeutic penetrating keratoplasty, or both (RR 0.61; 95% CI 0.40 to 0.94, 434 participants, high quality evidence). There was inconclusive evidence on time to clinical cure. Compliance with treatment and quality of life were not reported. One trial comparing natamycin and voriconazole found the effect of treatment greater in Fusarium species, but this subgroup analysis was not prespecified by this review.

AUTHORS' CONCLUSIONS

The trials included in this review were of variable quality and were generally underpowered. There is evidence that natamycin is more effective than voriconazole in the treatment of fungal ulcers. Future research should evaluate treatment effects according to fungus species.

Experience with Boston keratoprosthesis type 1 in the developing world

OBJECTIVE

To report the experience of the Federal University of São Paulo, Brazil, in performing Boston keratoprosthesis type 1 implantation in the developing world.

METHODS

We analyzed 30 eyes of 30 patients who underwent Boston type 1 keratoprosthesis surgery between 2008 and 2012 in a prospective interventional study. Preoperative, perioperative, and postoperative parameters were analyzed, including visual acuity (VA), keratoprosthesis stability, and postoperative complications.

RESULTS

Preoperative diagnoses were failed grafts in 16 eyes (53.33%), chemical injury in 10 eyes (33.33%) and Stevens-Johnson syndrome in 4 eyes (13.33%). Also, 16 eyes (53.33%) had preoperative glaucoma. Preoperative best corrected VA ranged from 20/400 to light perception. With an average follow-up of 32 months (range 1-55 months), postoperative vision improved to >20/200 in 24 eyes (80%). Postoperative VA was statistically improved compared with the preoperative measurement during all postoperative follow-ups (up to 36 months). During the follow-up period (32 months), retention of the initial keratoprosthesis was 93.3%. The incidence of retroprosthetic membrane was 26.66%. Progression of glaucoma occurred in 7 of 16 eyes (43%). Three patients experienced development of glaucoma after keratoprosthesis implantation. One eye experienced development of infectious keratitis, and 2 eyes had retinal detachment.

CONCLUSIONS

Performing Boston type 1 keratoprosthesis in a developing country is a viable option after multiple keratoplasty failures and conditions with a poor prognosis for keratoplasty. Our experience appears similar to major reports in the field from investigators in developed countries. Adjustments to postoperative management must be considered according to the particular location.

A new combination formula for treatment of fungal keratitis: an experimental study

Objective. To formulate and evaluate slow release ketoconazole and ketorolac to treat fungal keratitis and associated inflammation. Methods. Experimental study with the following outcome measures. Pharmaceutical Evaluation. Mucoadhesive gels containing ketoconazole and ketorolac were used. Microbiological in vitro evaluation was performed using cup method. In vivo evaluation was performed on 24 rabbits divided into 2 groups, 12 rabbits each, group A (fast release formula; 6 times daily) and group B (slow release formula; 3 times daily). Each group was divided into two subgroups (6 rabbits each). Both eyes of rabbits were inoculated with Candida albicans. The left eye of all rabbits received the combination formulae. The right eye for one subgroup received ketoconazole as control 1 while the other subgroup received placebo as control 2. Clinical follow-up was done and, finally, the corneas were used for microbiological and pathological evaluation. Results. Gels containing high polymer concentration showed both high viscosity and mucoadhesion properties with slower drug release. The infected eyes treated with slow release formula containing both drugs showed better curing of the cornea and pathologically less inflammation than eyes treated with fast release formula. Conclusion. Slow release formula containing ketoconazole and ketorolac showed higher activity than fast release formula against fungal keratitis and associated inflammation.

Aggressive Debridement Improves Outcome of Fungal Keratitis

PURPOSE

To study surgical debridement in the management of fungal keratitis in 44 patients.

DESIGN

A prospective randomized study.

METHODS

Patients with presumed fungal keratitis were randomized into 2 groups. The first group had diagnostic corneal scraping with a Kimura spatula while the second group underwent surgical debridement utilizing a motorized drill with attached diamond burr. Material obtained from both methods was plated on Sabaurauds medium, blood agar and stained for bacteria and fungi. Topical and systemic antifungal therapy was instituted, and patients were examined until resolution.

RESULTS

Pathogens were identified to a greater degree in the aggressive debridement group than in the Kimura spatula group. Patients who had aggressive debridement had a significant reduction in time to re-epithelialization and keratitis resolution (9.4 days) compared with the scraping group (17.1 days, P < 0.001). Mean uncorrected visual acuity (UCVA) in the surgical group was 1.02 logarithm of the minimal angle of resolution (logMAR) preoperatively and 0.43 logMAR postoperatively (P < 0.001). Mean UCVA in the Kimura spatula group was 1.20 logMAR before and 0.58 logMAR after scraping (P = 0.03). A single incidence of perforation occurred in the scraping group with the diagnosis of Fusarium made from the corneal button.

CONCLUSIONS

Aggressive debridement and debulking of fungal keratitis provides a faster clinical resolution with no reduction in visual potential. The acquisition of pathogens is more accurate with surgical debridement as compared with conventional scraping. Aggressive surgical debridement of keratitis not only aids in diagnosis but may also be therapeutic.

Assessment of fungal viability after long-wave ultraviolet light irradiation combined with riboflavin administration

BACKGROUND

Corneal collagen cross-linking (CXL), a technique that combines riboflavin administration with long-wave ultraviolet light irradiation, was primarily developed to increase the biomechanical strength of collagen fibrils of the cornea to avoid the progression of keratoconus. Recently, this method has been proposed to treat selected cases of infectious keratitis.

METHODS

To test the protocol used for progressive keratoconus in infectious keratitis, Candida albicans, and Fusarium solani, strains were exposed to irradiation using a wavelength of 365 nm at a power density of 3 mW/cm(2) for 30 min in the presence of riboflavin photosensitizer. All experiments were performed in triplicate. Qualitative and quantitative measurements of fungal viability used plate cultures and an automated trypan blue dye exclusion method respectively. Fungal cell diameter was also assessed in all groups. Statistical analyses were performed using the triplicate values of each experimental condition.

RESULTS

Experimental findings of photodynamic therapy applied to the cell inactivation of both yeasts and filamentous fungi were compared with control groups. Qualitative results were corroborated with quantitative findings which showed no statistical significance between challenged samples (experimental groups) and the control group (p-value = 1). In comparison with a control group of live cells, statistical significance was observed when riboflavin solution alone had an effect on the morphologic size of filamentous fungi, while ultraviolet light irradiation alone showed a slight decrease in the cell structure of C. albicans.

CONCLUSIONS

The impact of long-wave ultraviolet combined with riboflavin photosensitizer showed no antifungal effect on C. albicans and F. solani. The significant decrease in cell morphology of both filamentous fungi and yeasts submitted to photosensitizing riboflavin and exposure to ultraviolet light, respectively, may be promising in the development and standardization of alternatives for fungal cell inactivation, because of their minimal cytotoxic effects on the corneal surface. The methodological improvement in the preparation and application of individual chemical compounds, such as riboflavin, or physical systems, such as a long-wave light source, as antifungal agents may also assist in establishing promising therapeutic procedures for keratomycosis.

Medical interventions for fungal keratitis

BACKGROUND

Fungal keratitis is a fungal infection of the cornea. It is common in agricultural tropical countries but relatively uncommon in developed countries. Although there are medications available, their effectiveness is unclear.

OBJECTIVES

To examine the effect of different antifungal drugs in the management of fungal keratitis.

SEARCH METHODS

We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library 2011, Issue 8), MEDLINE (January 1950 to August 2011), EMBASE (January 1980 to August 2011), Latin American and Caribbean Literature on Health Sciences (LILACS) (January 1982 to August 2011), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com) and ClinicalTrials.gov (www.clinicaltrials.gov). There were no date or language restrictions in the electronic searches for trials. The electronic databases were last searched on 29 August 2011.

SELECTION CRITERIA

We included all relevant randomised controlled trials (RCTs) on medical therapy for fungal keratitis.

DATA COLLECTION AND ANALYSIS

Two review authors selected studies for inclusion into the review, assessed trials for risk of bias and extracted data. Interventions were compared by the proportions of participants that did not heal after a specific time of therapy. No meta-analysis was performed because the trials studied different medications with different concentrations.

MAIN RESULTS

We included nine trials in this review; seven conducted in India, one in Bangladesh and one in Egypt. A total of 568 participants were randomised to the following comparisons: 1% topical itraconazole versus 1% topical itraconazole and oral itraconazole, different concentrations of silver sulphadiazine versus 1% miconazole, 1% silver sulphadiazine ointment versus 1% miconazole ointment, 2% econazole versus 5% natamycin, different concentrations of topical chlorhexidine gluconate versus 5% natamycin, 0.2% chlorhexidine gluconate versus 2.5% natamycin and voriconazole 1% versus natamycin 5%. The included trials were small and of variable quality. Differences between different regimens were not statistically different, which may reflect the low sample sizes.

AUTHORS' CONCLUSIONS

Based on the trials included in this review, there is no evidence to date that any particular drug, or combination of drugs, is more effective in the management of fungal keratitis. The trials included in this review were of variable quality and were generally underpowered.

Medical interventions for fungal keratitis

BACKGROUND

Fungal keratitis is common in agricultural tropical countries but relatively uncommon in developed countries. Although there are medications available, their effectiveness is unclear.

OBJECTIVES

The purpose of the review was to examine the effect of different antifungal drugs in the management of fungal keratitis.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Group Trials Register) in The Cochrane Library (Issue 4, 2006), MEDLINE (1966 to January 2007), EMBASE (1980 to January 2007), LILACS (Latin American and Caribbean Literature on Health Sciences), reference lists of primary reports, review articles and conference proceedings. We contacted investigators and experts in the field for details of published and unpublished reports.

SELECTION CRITERIA

We included all relevant randomised controlled trials on medical therapy for fungal keratitis.

DATA COLLECTION AND ANALYSIS

Two review authors extracted and assessed trial quality. Interventions were compared by the proportions of participants that did not heal after a specific time of therapy. No meta-analysis was performed because the trials studied different medications with different concentrations.

MAIN RESULTS

Six trials were identified which compared different antifungal drugs namely: 1% topical itraconazole versus 1% topical itraconazole and oral itraconazole, different concentrations of silver sulphadiazine versus 1% miconazole, 1% silver sulphadiazine ointment versus 1% miconazole ointment, 2% econazole versus 5% natamycin, different concentrations of topical chlorhexidine gluconate versus 5% natamycin, and 0.2% chlorhexidine gluconate versus 2.5% natamycin. A total of 370 participants were randomised. No single reference drug was used. All trials considered clinical cure as primary outcome. Comparing treatment effects of all the drug preparations studied, silver sulphadiazine ointment had the lowest proportion of participants with treatment failure followed by itraconazole, miconazole, chlorhexidine, econazole, and the drug with the most treatment failure was natamycin. These differences were not, however, statistically significant which might in part be due to low sample sizes.

AUTHORS' CONCLUSIONS

There is no evidence that the current available and investigational antifungal agents are effective. The review identified the need for large multicentre randomised trials.

Antifungal therapy for keratomycoses

Keratomycoses have recently emerged as an important cause of ocular morbidity, especially in third-world countries. Available antifungal agents are limited in their efficacy, due to limited penetration into the cornea, the fungistatic nature and the development of drug resistance. Effective usage of the available drugs is hampered by the inefficiency of currently available antibiotic sensitivity tests for fungal organisms. There is also limited knowledge regarding the ideal combination(s) of antifungal agents, including issues of synergism and antagonism. Despite these problems, recent publications indicate encouraging outcomes in the treatment of a large series of fungal keratitis. Advances include better drug formulations, new agents and novel methods of drug delivery into the eye. As our ability to deal with advanced fungal keratitis remains limited, the importance of early diagnosis has been stressed and molecular biological techniques may play an important role in the future. This article summarises the important new advances in these areas in the past 2 years and provides guidelines for the management of these serious corneal infections.

A randomised trial of povidone-iodine to reduce visual impairment from corneal ulcers in rural Nepal

AIM

To assess whether povidone-iodine provided any benefit over and above a standard regimen of antibiotic therapy for the treatment of corneal ulcers.

METHODS

All patients diagnosed with corneal ulcers presenting for care at a primary eye care clinic in rural Nepal were randomised to a standard protocol of antibiotic therapy versus standard therapy plus 2.5% povidone-iodine every 2 hours for 2 weeks. The main outcomes were corrected visual acuity and presence, size, and position of corneal scarring in the affected eye at 2-4 months following treatment initiation.

RESULTS

358 patients were randomised and 81% were examined at follow up. The two groups were comparable before treatment. At follow up, 3.9% in the standard therapy and 6.9% in the povidone-iodine group had corrected visual acuity worse than 20/400 (relative risk (RR) 1.77, 95% confidence interval (CI) 0.62 to 5.03). 9.4% in the standard therapy and 13.1% in the povidone-iodine group had corrected visual acuity worse than 20/60 (RR 1.39, 95% CI 0.71 to 2.77), and 17.0% and 18.8% had scars in the visual axis in each of these groups, respectively (RR 1.11, 95% CI 0.67 to 1.82).

CONCLUSIONS

A small proportion of patients with corneal ulceration treated in this setting had poor visual outcomes. The addition of povidone-iodine to standard antibiotic therapy did not improve visual outcomes, although this design was unable to assess whether povidone-iodine on its own would have resulted in comparable visual outcomes to that of standard therapy.

Adsorption of cationic antibacterial on collagen-coated titanium implant devices

Two different cationic antimicrobial molecules, chlorhexidine (CH) and poly(hexamethylenebiguanide) (PH), were adsorbed from aqueous solution to titanium implant devices surface-modified by the covalent coupling of collagen on a polyanionic acrylic acid overlayer. Results show that more antimicrobial was adsorbed on surface modified implants as compared to control titanium devices. Moreover, the kinetic of release was affected by the interaction between the polyanionic overlayer and the cationic antimicrobial, leading to slower kinetic of release in the case of CH and stable adsorption in the case of polycationic PH . These data indicate that biochemically modified collagen coated surfaces could be endowed also by antimicrobial properties, in the spirit of present researches on multifunctional implant surfaces.

Role of 0.02% polyhexamethylene biguanide and 1% povidone iodine in experimental Aspergillus keratitis

PURPOSE

To determine the efficacy of 0.02% polyhexamethylene biguanide and 1% povidone iodine in experimental keratitis.

METHODS

Aspergillus fumigatus keratitis was induced by corneal intrastromal injection of spores in 24 healthy rabbits that were randomly divided into four groups of six rabbits each. Drugs used were 5% natamycin (standard antifungal), 0.02% polyhexamethylene biguanide (PHMB) (test drug), 1% povidone iodine (test drug), and 0.5% hydroxypropylmethyl cellulose (HPMC) (control).

RESULTS

The average healing times of the ulcer were 21.5 +/- 3.08 days with 5% natamycin, 27.8 +/- 2.28 days with 0.02% PHMB, 36.4 +/- 2.57 days with 1% povidone iodine, and 38.2 +/- 4.74 days with 0.5% HPMC. While no corneal perforations occurred with natamycin treatment, one perforation was noted with PHMB, three perforations were noted with povidone iodine, and five perforations were noted with controls.

CONCLUSION

Polyhexamethylene biguanide (0.02%) is a moderately effective drug for experimental Aspergillus keratitis, but 1% povidone iodine is not effective.

Pharmacotherapy of fungal eye infections

Fungal eye infections are rare. Trauma associated with contamination by vegetative material, contact lens wear and long term corticosteroid use are common risk factors. The aims of treatment are to preserve visual function, which depends on the rapid diagnosis and efficient administration of appropriate antifungal therapy. This necessitates a clinical suspicion of fungal aetiology and the taking of appropriate smears and cultures as early as possible to identify the fungal organism. Currently there are three main classes of drugs available for use in fungal eye infections: polyenes, azoles as derivatives of imidazoles, and 5-fluorocytosine. Of the polyenes, amphotericin B, natamycin and nystatin are of clinical ophthalmic use. Based on better pharmacokinetic profiles and spectra of antifungal activity, the triazoles are the agents of choice. Successful treatment of fungal keratitis depends on early initiation of specific therapy consisting of topically-applied antifungal agents since topical administration is most likely to provide the best opportunity for achieving therapeutic corneal levels. Hence, the molecular weight of the various antifungal agents is of importance since it influences their ability to penetrate the corneal epithelium. Systemic administration may be necessary for resistant fungal ulcers. For fungal endophthalmitis, to preserve visual function and eliminate the fungal pathogen, topical, systemic and possibly intraocular antifungal therapy is used, although some do not recommend use of systemic agents for exogenous endophthalmitis.

Fungal and parasitic infections of the eye

The unique structure of the human eye as well as exposure of the eye directly to the environment renders it vulnerable to a number of uncommon infectious diseases caused by fungi and parasites. Host defenses directed against these microorganisms, once anatomical barriers are breached, are often insufficient to prevent loss of vision. Therefore, the timely identification and treatment of the involved microorganisms are paramount. The anatomy of the eye and its surrounding structures is presented with an emphasis upon the association of the anatomy with specific infection of fungi and parasites. For example, filamentous fungal infections of the eye are usually due to penetrating trauma by objects contaminated by vegetable matter of the cornea or globe or, by extension, of infection from adjacent paranasal sinuses. Fungal endophthalmitis and chorioretinitis, on the other hand, are usually the result of antecedent fungemia seeding the ocular tissue. Candida spp. are the most common cause of endogenous endophthalmitis, although initial infection with the dimorphic fungi may lead to infection and scarring of the chorioretina. Contact lens wear is associated with keratitis caused by yeasts, filamentous fungi, and Acanthamoebae spp. Most parasitic infections of the eye, however, arise following bloodborne carriage of the microorganism to the eye or adjacent structures.

Fungal and parasitic infections of the eye

The unique structure of the human eye as well as exposure of the eye directly to the environment renders it vulnerable to a number of uncommon infectious diseases caused by fungi and parasites. Host defenses directed against these microorganisms, once anatomical barriers are breached, are often insufficient to prevent loss of vision. Therefore, the timely identification and treatment of the involved microorganisms are paramount. The anatomy of the eye and its surrounding structures is presented with an emphasis upon the association of the anatomy with specific infection of fungi and parasites. For example, filamentous fungal infections of the eye are usually due to penetrating trauma by objects contaminated by vegetable matter of the cornea or globe or, by extension, of infection from adjacent paranasal sinuses. Fungal endophthalmitis and chorioretinitis, on the other hand, are usually the result of antecedent fungemia seeding the ocular tissue. Candida spp. are the most common cause of endogenous endophthalmitis, although initial infection with the dimorphic fungi may lead to infection and scarring of the chorioretina. Contact lens wear is associated with keratitis caused by yeasts, filamentous fungi, and Acanthamoebae spp. Most parasitic infections of the eye, however, arise following bloodborne carriage of the microorganism to the eye or adjacent structures.

Randomised trial of 0.2% chlorhexidine gluconate and 2.5% natamycin for fungal keratitis in Bangladesh

AIM

The management of suppurative keratitis due to filamentous fungi presents severe problems in tropical countries. The aim was to demonstrate the efficacy of chlorhexidine 0.2% drops as an inexpensive antimicrobial agent, which could be widely distributed for fungal keratitis.

METHODS

Successive patients presenting to the Chittagong Eye Institute and Training Complex with corneal ulcers were admitted to the trial when fungal hyphae had been seen on microscopy. They were randomised to drop treatment with chlorhexidine gluconate 0.2% or the standard local treatment natamycin 2.5%. The diameters, depths, and other features of the ulcers were measured and photographed at regular intervals. The outcome measures were healing at 21 days and presence or absence of toxicity. If there was not a favourable response at 5 days, "treatment failure" was recorded and the treatment was changed to one or more of three options, which included econazole 1% in the latter part of the trial.

RESULTS

71 patients were recruited to the trial, of which 35 were randomised to chlorhexidine and 36 to natamycin. One allocated to natamycin grew bacteria and therefore was excluded from the analysis. None of the severe ulcers was fully healed at 21 days of treatment, but three of those allocated to chlorhexidine eventually healed in times up to 60 days. Of the nonsevere ulcers, 66.7% were healed at 21 days with chlorhexidine and 36.0% with natamycin, a relative efficacy (RE) of 1.85 (CL 1.01-3.39, p = 0.04). If those ulcers were excluded where fungi were seen in the scraping but did not grow on culture, the estimated efficacy ratio does not change but becomes less precise because of smaller numbers. Equal numbers of Aspergillus (22) and Fusarium (22) were grown. The Aspergillus were the most resistant to either primary treatment.

CONCLUSIONS

Chlorhexidine may have potential as an inexpensive topical agent for fungal keratitis and warrants further assessment as a first line treatment in situations where microbiological facilities and a range of antifungal agents are not available.

Antimicrobial management of presumed microbial keratitis: guidelines for treatment of central and peripheral ulcers

AIMS

To determine the quantitative relation between the major risk factors for microbial keratitis of previous ocular surface disease and contact lens wear and central and peripheral infiltration, often associated with ulceration, in order to establish a rational chemotherapeutic management algorithm.

METHODS

Data from 55 patients were collected over a 10 month period. All cases of presumed microbial keratitis where corneal scrapes had been subjected to microbiological examination were included. Risk factor data and laboratory outcome were recorded. Antimicrobial regimens used to treat each patient were documented.

RESULTS

57 episodes of presumed microbial keratitis were identified from 55 patients, 24 male and 31 female. There were 30 central infiltrates and 27 peripheral infiltrates of which 28 were culture positive (73% of central infiltrates, 22% of peripheral infiltrates). 26 patients had worn contact lenses of whom 12 had culture positive scrapes (9/14 for central infiltrates, 3/12 for peripheral infiltrates). 31 patients had an ocular surface disease of whom five previous herpes simplex virus keratitis patients developed secondary bacterial infection. Anterior chamber activity and an infiltrate size > or = 4 mm2 were more common with culture positive central infiltrates than peripheral infiltrates (chi 2 test = 11.98, p < 0.001).

CONCLUSIONS

Predisposing factors for "presumed" microbial keratitis, either central or peripheral, were: ocular surface disease (26/57 = 45.6%), contact lens wear (26/57 = 45.6%), and previous trauma (5/57 = 8.8%). Larger ulceration (> or = 4 mm2) with inflammation was more often associated with positive culture results for central infiltration. None of these four variables (contact lens wear, ocular surface disease, ulcer size, anterior chamber activity) were of intrinsic value in predicting if a peripheral infiltrate would yield identifiable micro-organisms. Successful management of presumed microbial keratitis is aided by a logical approach to therapy, with the use of a defined algorithm of first and second line broad spectrum antimicrobials, for application at each stage of the investigative and treatment process considering central and peripheral infiltration separately.

Trial of chlorhexidine gluconate for fungal corneal ulcers

AIMS

Suppurative corneal ulcers due to filamentous fungi are a serious and intractable problem in many tropical developing countries. In vitro studies and a small pilot study have shown that chlorhexidine gluconate is effective. The aim was to establish the optimum concentration which would be appropriate to use in a larger randomized clinical trial.

METHODS

A masked randomized clinical trial of three concentrations of chlorhexidine compared with natamycin 5% was carried out in consecutive patients with established corneal ulcers shown by microscopy to contain fungal hyphae and later proven to be culture positive. Topical treatments were applied 1/2-hourly to 2-hourly for up to 5 days, with reduced frequency thereafter, and all patients were re-assessed at 21 days.

RESULTS

Of 60 patients entered in the trial, 2 were lost to follow-up, and 12 were classified as 'severe' with little prospect of recovery. At 5 days the response was related to the concentration of chlorhexidine, with 0.2% giving the best results. Compared with the response to natamycin as the referent, the relative efficacy was 1.17 with chlorhexidine 0.05%, 1.43 with 0.1%, and 2.00 with 0.2%. The superiority of 0.2% chlorhexidine over natamycin was statistically significant (relative efficacy 2.20, p = 0.043) in patients not having had prior antifungal treatment.

CONCLUSIONS

This preliminary study justifies further trials of chlorhexidine as a primary treatment for fungal corneal ulcers in circumstances where specific antifungal agents are not available.