Use of corticosteroids in combination with antimicrobial drugs in the treatment of infectious corneal disease

Prescribing trends in infectious keratitis: a survey of New Zealand ophthalmologists

PURPOSE

To obtain an overview of the treatment of infectious diseases of the cornea by New Zealand ophthalmologists and to analyse the data in the context of evidence-based treatment recommendations.

METHODS

A questionnaire was sent to all New Zealand ophthalmologists. It comprised 23 multiple-choice questions pertaining to the characteristics of the respondents, the nature of their practice and their prescribing preferences in infectious conjunctivitis and keratitis.

RESULTS

Of the 93 ophthalmologists surveyed, 80.6% returned the questionnaire. Of those in clinical practice, 91.4% regularly treated patients with corneal disease. A subspecialty interest in cornea was stated by 12.5% of these. This paper reports observations for adenoviral conjunctivitis and adenoviral, Herpes simplex, varicella zoster, bacterial, acanthamoebal and fungal keratitis. In some conditions prescribing practice varied dramatically, such as in adenoviral conjunctivitis where 50% of respondents prescribed a corticosteroid and 51.6% an antibiotic, whereas 37.5% prescribed only lubrication or no topical treatment. In other conditions there was a high degree of agreement between ophthalmologists; indeed, all ophthalmologists treated Herpes simplex dendritic keratitis with topical acyclovir. No statistically significant differences in prescribing habits were identified between subspecialist and non-subspecialist groups, although some important clinical differences emerged. There were occasional marked differences in response when the age group of respondents was considered, particularly in relation to the management of adenoviral infections and bacterial keratitis.

CONCLUSIONS

The findings of this survey suggest that the majority of New Zealand ophthalmologists generally follow international guidelines for the management of infectious keratitis. The identified variations in management provide a foundation for informed clinical debate and the development of treatment guidelines, in line with evidence-based recommendations.

Fungal infections of the cornea

PURPOSE

To describe key aspects of fungal infections of the cornea, which constitute an important eye problem in outdoor workers in tropical and subtropical regions.

METHODS

Review of published studies and personal observations.

OBSERVATIONS

Fungal infections of the cornea are frequently caused by species of Fusarium, Aspergillus, Curvularia, and Candida. Trauma is the most important predisposing cause; ocular and systemic defects and prior application of corticosteroids are also important risk factors. Culture remains the cornerstone of diagnosis; direct microscopic detection of fungal structures in corneal scrapes or biopsies permits a rapid presumptive diagnosis. A variety of antifungals have been evaluated in therapy of this condition. Natamycin can only be given topically, while amphotericin B, miconazole, ketoconazole, itraconazole, and fluconazole can be administered by various routes. Topical amphotericin B (0.1-0.3%) is frequently the treatment of choice for infections due to Candida and related fungi, while topical natamycin (5%) is the choice for keratitis due to filamentous fungi. Medical therapy may fail, necessitating surgical intervention.

CONCLUSIONS

Fungal infections of the cornea continue to be an important cause of ocular morbidity, particularly in the agricultural communities of the developing world. A proper understanding of agent and host factors involved in these infections will improve the outcome of this condition.

Current perspectives on ophthalmic mycoses

Fungi may infect the cornea, orbit and other ocular structures. Species of Fusarium, Aspergillus, Candida, dematiaceous fungi, and Scedosporium predominate. Diagnosis is aided by recognition of typical clinical features and by direct microscopic detection of fungi in scrapes, biopsy specimens, and other samples. Culture confirms the diagnosis. Histopathological, immunohistochemical, or DNA-based tests may also be needed. Pathogenesis involves agent (invasiveness, toxigenicity) and host factors. Specific antifungal therapy is instituted as soon as the diagnosis is made. Amphotericin B by various routes is the mainstay of treatment for life-threatening and severe ophthalmic mycoses. Topical natamycin is usually the first choice for filamentous fungal keratitis, and topical amphotericin B is the first choice for yeast keratitis. Increasingly, the triazoles itraconazole and fluconazole are being evaluated as therapeutic options in ophthalmic mycoses. Medical therapy alone does not usually suffice for invasive fungal orbital infections, scleritis, and keratitis due to Fusarium spp., Lasiodiplodia theobromae, and Pythium insidiosum. Surgical debridement is essential in orbital infections, while various surgical procedures may be required for other infections not responding to medical therapy. Corticosteroids are contraindicated in most ophthalmic mycoses; therefore, other methods are being sought to control inflammatory tissue damage. Fungal infections following ophthalmic surgical procedures, in patients with AIDS, and due to use of various ocular biomaterials are unique subsets of ophthalmic mycoses. Future research needs to focus on the development of rapid, species-specific diagnostic aids, broad-spectrum fungicidal compounds that are active by various routes, and therapeutic modalities which curtail the harmful effects of fungus- and host tissue-derived factors.

Severe infective keratitis leading to hospital admission in New Zealand

AIM

To identify key risk factors and the management and outcome of severe infective keratitis leading to public hospital admission in New Zealand.

METHODS

Over a 2 year period, all admissions of presumed infective keratitis to Auckland Hospital were identified. The clinical records of all 103 cases were retrospectively reviewed with respect to clinical features, risk factors, management, and outcomes.

RESULTS

The mean time from first symptoms or signs and presentation to hospital was 8.9 (SD 15.5) days. The majority of subjects, 88%, had at least one of the risk factors commonly associated with infective keratitis including previous ocular surgery (30%), contact lens wear (26%), topical corticosteroid use (25%), and ocular trauma (24%). Corneal scraping was performed in 92% and of a total of 105 scrapes, 71% were positive. Bacteria were isolated in all these cases, the majority being Gram positive organisms (72%). The most common isolates identified were coagulase negative Staphylococcus (16%), Propionibacterium acnes (14%), Staphylococcus epidermidis (11%), and Streptococcus pneumoniae (9%). In addition, yeasts were isolated in 5%, fungi in 4%, virus in 2%, and chlamydia in 1%. Importantly, polymicrobial infection accounted for 33% of culture positive cases. Antimicrobial treatment was changed on the basis of culture results in 17 cases (16.5%). Median initial visual and final best corrected visual acuity was 6/36-6/48 (logMAR 0.86) (IQR 0.39-2.00) and 6/12-6/15 (logMAR 0.360) (IQR 0.15-1.70), respectively. Previous ocular surgery and topical corticosteroid use were significantly associated with poorer visual acuity. The mean hospital stay was 5.8 days and the median 4.0 (IQR 2.0-8.0) days. Longer duration of stay was associated with the presence of hypopyon, larger ulcers, previous ocular surgery, and poor visual acuity.

CONCLUSIONS

Infectious keratitis is an important cause of ocular morbidity. A significant proportion of cases have potentially modifiable risk factors. Previous ocular surgery and topical corticosteroid use, in particular, were associated with poorer visual outcomes. Many cases of severe keratitis might be avoided, or their severity reduced, by appropriate education of patients and ophthalmologists.

Persistently culture positive acanthamoeba keratitis: in vivo resistance and in vitro sensitivity

PURPOSE

To characterize the risk factors, clinical course, treatment outcome and the association between in vivo resistance and in vitro sensitivity for subjects with persistently culture-positive Acanthamoeba keratitis.

DESIGN

Retrospective noncomparative case series.

PARTICIPANTS

Eleven subjects with repeatedly positive cultures for Acanthamoeba treated between January 1990 and December 2000, were reviewed. Only subjects with 2 or more positive cultures, availability of the clinical data, and availability of the last Acanthamoeba isolate were included in this study.

METHODS

The medical records were analyzed, and the last isolate from each case was tested in vitro for the antiamoebic drugs used clinically: polyhexamethylene biguanide (PHMB), chlorhexidine, propamidine and hexamidine.

MAIN OUTCOME MEASURES

Risk factors, the clinical outcome and in vitro cysticidal drug sensitivity assay.

RESULTS

Eleven subjects (11/180, 6.1%) had 2 or more positive cultures of whom 8 eyes of 8 subjects (8/180, 4.45%) were included in this study. Seven of eight (87%) subjects were diagnosed over 1 month from onset (late diagnosis). The most common presenting findings were diffuse stromal infiltrate (5/8, 62.5%), ring infiltrate (5/8, 62.5%), and corneal ulceration (3/8, 37.5%). The clinical course of the disease in all subjects consisted of recurrent episodes of corneal and scleral inflammation, with a mean duration of 13.4 +/- 9 months. All subjects received PHMB, and 5/8 (62.5%) chlorhexidine too; hexamidine was used in combination in 6/8 (75%), and propamidine in 1/8 (12.5%). All subjects had topical steroids, and 5/8 (62.5%) systemic immunosuppression. The disease resolved with corneal scarring in 3/8 (37.5%) subjects, corneal (or impending) perforation treated with therapeutic keratoplasty in 4/8 (50%), and enucleation in 1/8 (12.5%). Final visual acuity was 0.43 +/- 0.37. In vitro most isolates were resistant to propamidine, hexamidine was cysticidal in high concentrations, and PHMB and chlorhexidine had excellent sensitivity profiles.

CONCLUSIONS

In our large series of Acanthamoeba keratitis with a positive microbiologic diagnosis at presentation, nearly 5% developed recurrent episodes of corneal and scleral inflammation with viable Acanthamoeba in the cornea despite prolonged treatment with biguanides and/or diamidines. There was no correlation between in vitro drug sensitivities and the in vivo response for biguanides.

Advanced fusarium keratitis progressing to endophthalmitis

PURPOSE

To review the clinical course, treatment, and visual outcomes of keratitis with endophthalmitis caused by the filamentary fungus Fusarium.

METHOD

One hundred fifty-nine cases of Fusarium keratitis at Bascom Palmer Eye Institute between January 1, 1987 and August 21, 2000 were reviewed. Ten patients with culture-proven Fusarium keratitis progressed to endophthalmitis. All 10 underwent standard diagnostic microbiologic evaluation, and topical and oral antifungal therapy was instituted. Surgical therapy was applied when necessary. Main outcome measures included the incidence of intraocular invasion of fungal keratitis and response to treatment.

RESULTS

Ten cases of 159 Fusarium keratitis patients had intraocular involvement that was culture proven. The isolated species were Fusarium oxysporum in seven cases and Fusarium solani in two cases, and in one case, the species could not be identified. Cultures of aqueous and intraocular tissues grew Fusarium in eight cases, whereas vitreous cultures were positive in two. Nine cases had preexisting risk factors. All patients received oral ketoconazole or fluconazole and topical natamycin 5%. In two cases, intravitreal amphotericin B injections were also given. Four patients required a penetrating keratoplasty, enucleation was performed in two patients, two patients required a combination of a penetrating keratoplasty and pars plana vitrectomy, and one patient developed phthisis.

CONCLUSION

The combination therapy with oral imidazoles (fluconazole or ketoconazole) and topical natamycin is inadequate in severe Fusarium keratitis with intraocular spread. Early diagnosis and suspicion of endophthalmitis in patients with keratomycosis not responding to aggressive topical antifungal are important.

Corneal ulceration in pediatric patients: a brief overview of progress in topical treatment

Pediatric microbial keratitis is a rare but potentially devastating condition. The condition is similar to adult microbial keratitis, but is often characterized by a more severe inflammatory response. The micro-organisms that cause microbial keratitis in children are similar to the causative agents in adults, with herpes simplex and bacteria being the predominant causative agents, and fungi being less frequent. Of the bacterial pathogens, Pseudomonas aeruginosa, Staphylococcus aureus and alpha-hemolytic streptococci are common. The risk factors for pediatric keratitis include colonization of the eyes during birth and trauma to the cornea. Certain microbial factors involved in microbial keratitis are common to all micro-organisms, including adhesion to the cornea, penetration into the cornea, destruction of the corneal stroma (usually by microbial and/or host proteases), and recruitment of white blood cells to help defend the eye. Specific inflammatory responses that occur during pediatric microbial keratitis are not known in detail, but it is likely that cytokines and polymorphonuclear leucocytes are major factors, as they are in adult microbial keratitis. Treatment for pediatric microbial keratitis is usually the same as treatment for adult microbial keratitis; topical application of antimicrobial agents initially, followed by application of anti-inflammatory agents. With pediatric microbial keratitis, extra care must be taken to ensure nontoxicity due to blood adsorption. New microbial keratitis treatments are being developed and these mainly focus on new antimicrobials, antivirulence agents (such as vaccination against microbial toxins) or specific anti-inflammatory agents. There remains a clear need for increased research into the specific responses during microbial keratitis in children which will help progress new therapies as well as the development of new antimicrobials, especially new antifungal therapies.

Locally administered ocular corticosteroids: benefits and risks

Corticosteroids, used prudently, are one of the most potent and effective modalities available in the treatment of ocular inflammation. However, they can produce a plethora of adverse ocular and systemic events. In order to optimise and target drug delivery, whilst minimising systemic adverse effects, a diverse range of local ophthalmic preparations and delivery techniques have been developed. Topical drops and ointments remain the primary methods for administration of ocular corticosteroids. However, ocular penetration of topical corticosteroid drops depends upon drug concentration, chemical formulation of corticosteroid, and composition of the vehicle, therefore, apparently small modifications in preparations can produce a more than 20-fold difference in intraocular drug concentration. Periocular injections of corticosteroids continue to have a useful, but limited, therapeutic role and longer acting, intraocular delayed-release devices are in early clinical studies. Although newer corticosteroids with lesser pressure elevating characteristics have been developed, corticosteroid-induced ocular hypertension and glaucoma continue to be significant risks of local and systemic administration. Posterior subcapsular cataract, observed following as little as 4 months topical corticosteroids use, is thought to be due to covalent binding of corticosteroid to lens protein with subsequent oxidation. Inappropriate use of topical corticosteroid in the presence of corneal infections also continues to be a cause of ocular morbidity. Other risks of locally administered ophthalmic corticosteroids include: tear-film instability, epithelial toxicity, crystalline keratopathy, decreased wound strength, orbital fat atrophy, ptosis, limitation of ocular movement, inadvertent intraocular injection, and reduction in endogenous cortisol. This extensive review assesses the therapeutic benefits of locally administered ocular corticosteroids in the context of the risks of adverse effects.

Indecision about corticosteroids for bacterial keratitis: an evidence-based update

PURPOSE

To quantify the effect of topical corticosteroids on bacterial keratitis.

CLINICAL RELEVANCE

Bacterial keratitis is an economically important infection affecting 1 in 10,000 Americans annually. The predisposing factors, prior ocular health, infecting microorganisms, inflammatory severity, and therapeutic choices can affect the course and outcome. Antibacterial treatment is often curative but does not guarantee good vision. Because many treated patients develop a sight-limiting corneal problem, antiinflammatory therapy has sometimes been recommended.

LITERATURE REVIEWED

Publications from 1950 to 2000 that evaluated the effect of corticosteroids on bacterial keratitis in animal experiments, case reports and series, case-comparison and cohort studies, and clinical trials were systematically identified by electronic and manual search strategies.

RESULTS

The use of a topical corticosteroid before the diagnosis of bacterial keratitis significantly predisposed to ulcerative keratitis in eyes with preexisting corneal disease (odds ratio [OR], 2.63; 95% confidence limits [CL], 1.41, 4.91). Once microbial keratitis occurred, prior corticosteroid use significantly increased the odds of antibiotic treatment failure or other infectious complications (OR, 3.75; 95% CL, 2.52, 5.58). However, the effect of a topical corticosteroid with antibiotics after the onset of bacterial keratitis was unclear. Experimental models suggested likely advantages, but clinical studies did not show a significant effect of topical corticosteroid therapy on the outcome of bacterial keratitis (OR, 0.62; 95% CL, 0.25, 1.54).

CONCLUSIONS

Topical corticosteroids increase the risk of infectious complications affecting the cornea but may or may not have an effect during antibacterial therapy. The unproven role of corticosteroids in the adjunctive treatment of bacterial keratitis highlights the need to collect prospective information that would guide appropriate management for this common eye disease.

Topical cyclosporin A in the management of therapeutic keratoplasty for mycotic keratitis

PURPOSE

To investigate the efficacy of topical cyclosporine A 0.5% as a substitute for corticosteroids in the management of therapeutic keratoplasties for mycotic keratitis.

METHODS

Prospective, nonrandomized interventional case series. Three patients with culture-proven mycotic keratitis underwent therapeutic keratoplasties. All were treated with topical cyclosporine A 0.5% postoperatively as a primary or an adjunctive therapy for prevention of allograft rejection. The patients were followed up from 15 to 42 months for maintenance of graft clarity and best-corrected visual acuity.

RESULTS

Two of three patients maintained clear grafts while using topical cyclosporine A 0.5% twice daily with best-corrected visual acuity of 20/40 and 20/50. One patient developed an opacified graft secondary to preexisting ocular surface disease.

CONCLUSIONS

Topical cyclosporine A 0.5% may be a useful adjunct in the management of therapeutic keratoplasties for mycotic keratitis.

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.

S, Feild CJ, Block EF, Michael L. C. An Unusual Case of Corneal Perforation Secondary to Pseudomonas Keratitis Complicating a Patient's Surgical/Trauma Intensive Care Unit Stay

We report a case of corneal perforation secondary to bacterial keratitis caused by Pseudomonas aeruginosa in a trauma patient in our intensive care unit. A 43-year-old man was involved in a motorcycle crash and suffered multiple injuries necessitating a prolonged intensive care unit (ICU) stay. Subsequently P. aeruginosa was cultured from his sputum, blood, and open abdomen. He developed a bacterial keratitis in his right eye, which also grew P. aeruginosa. This infection rapidly progressed to corneal perforation requiring a Gunderson conjunctival flap and lateral tarsorrhaphy in addition to aggressive antibiotic treatment. At the time of discharge from the hospital the patient had the return of vision to light only in his right eye. Corneal perforation is an unusual event in the ICU. Prevention or early detection of bacterial keratitis with aggressive antibiotic treatment is needed to prevent such complications. Pseudomonas is one of the more virulent organisms that can infect the cornea and early identification is paramount for a good outcome. Management of this complicated case is discussed and the limited amount of literature on nosocomial bacterial keratitis in the ICU is reviewed.

Risk factors for treatment outcome of suspected microbial keratitis. Ofloxacin Study Group

BACKGROUND

Primary treatment for suspected microbial keratitis is generally successful. Although risks such as contact lens use are well recognised as causative factors for microbial keratitis, little is known about the risk factors that influence treatment outcome. The present study evaluates the risk factors assessed at diagnosis as prognostic indicators of primary treatment failure.

METHODS

Patients were prospectively enrolled in the ofloxacin treatment trial and data concerning symptoms, treatments, past and concurrent eye disease were collected along with the measurement of corneal ulcer size at the slit lamp. All patients were scraped for microbiological investigation, and treated with either ofloxacin (0. 3%) or standard therapy of fortified cefuroxime and gentamicin drops. Treatment success was complete healing of the ulcer with zero dimensions of the epithelial defect within 2 weeks of start of treatment. The important prognostic indicators were selected by comparison among those who failed treatment, had delayed healing, or were culture positive with other patients using univariate and stratified analysis. These were then used in a Poisson model for multiple regression analysis to estimate the relative risk of the main prognostic variables.

RESULTS

Of the 118 patients enrolled in the study, 14 were identified as primary treatment failures, 17 had slow healing, and 15 indolent ulcers. There were 49 culture positive patients. The multivariate analysis identified that large culture positive ulcers in patients 60 years or older had 5.5 times the risk of primary treatment failure (p<0.001). Significant predictors of slow healing were previous ocular disease and a positive culture; significant predictors of indolent ulceration were previous ocular disease and steroid use at diagnosis; the main predictor of a culture positive result was ulcer size.

CONCLUSIONS

Elderly patients with large ulcers were more likely to be culture positive, fail primary therapy, and require surgical intervention. A positive microbial culture provided prognostic information regardless of the organism isolated. However, this information was of less value for those with small ulcers and for younger patients.

Results of a trial of combined propamidine isethionate and neomycin therapy for Acanthamoeba keratitis. Brolene Study Group

PURPOSE

To characterize patients with Acanthamoeba keratitis and to evaluate the safety and efficacy of propamidine isethionate 0.1% ophthalmic solution (Brolene) when administered concomitantly with neomycin-polymyxin B-gramicidin ophthalmic solution (Neotricin) in the treatment of Acanthamoeba keratitis.

DESIGN

Prospective, noncomparative case series.

METHODS

The authors report the clinical characteristics and outcomes of patients who entered this multicentered, open-label, clinical trial. Eighty-three patients with Acanthamoeba keratitis representing 87 infected eyes entered the trial.

RESULTS

Sixty (69%) of the 87 eyes enrolled had data analyzed for treatment efficacy and safety. Of these 60 eyes, 50 (83%) experienced treatment success. Thirty (60%) patients successfully treated adhered to treatment protocol guidelines. Patients who broke protocol had disease exacerbation during the maintenance therapy phase. The only eyes lost/enucleated were 7 of 17 in which penetrating keratoplasty was performed before eradication of the infectious agent.

CONCLUSION

Propamidine isethionate and neomycin are an effective treatment for Acanthamoeba keratitis. Penetrating keratoplasty should be performed only for visual rehabilitation and not to "debulk" an active infection. The authors advocate treating patients with topical medications, mainly Brolene, until all organisms are eradicated. There should be no signs of infection for at least 3 months in the patients not receiving antiamebic medications before penetrating keratoplasty is performed.

Indiscriminate use of corticosteroid-containing eyedrops

Ocular complications may occur with the use of corticosteroid-containing eyedrops. We describe two cases of corticosteroid-induced glaucoma and one case of corticosteroid-associated fungal keratitis. Corticosteroid-containing eyedrops should be avoided unless the practitioner is knowledgeable about tonometry, slit-lamp examination techniques, and ocular differential diagnosis and treatment. Alternative pharmacologic approaches to topical administration of corticosteroid-containing eyedrops are discussed.

Acanthamoeba keratitis

Acanthamoeba species are an important cause of microbial keratitis that may cause severe ocular inflammation and visual loss. The first cases were recognized in 1973, but the disease remained very rare until the 1980s, when an increase in incidence mainly associated with contact lens wear was reported. There is an increased risk when contact lens rinsing and soaking solutions are prepared with nonsterile water and salt tablets. The clinical picture is often characterized by severe pain with an early superficial keratitis that is often treated as herpes simplex infection. Subsequently a characteristic radial perineural infiltration may be seen, and ring infiltration is common. Limbitis and scleritis are frequent. Laboratory diagnosis is primarily by culture of epithelial samples inoculated onto agar plates spread with bacteria. Direct microscopy of samples using stains for the cyst wall or immunostaining may also be employed. A variety of topically applied therapeutic agents are thought to be effective, including propamidine isethionate, clotrimazole, polyhexamethylene biguanide, and chlorhexidine. Various combinations of these and other agents have been employed, often resulting in medical cure, especially if treatment is commenced early in the course of the disease. Penetrating keratoplasty is preferably avoided in inflamed eyes, but may be necessary in severe cases to preserve the globe or, when the infection has resolved, to restore corneal clarity for optical reasons.

Optimized release of dexamethasone and gentamicin from a soluble ocular insert for the treatment of external ophthalmic infections

In the case of external ophthalmic infections, repeated instillations of antibiotics are required to reach therapeutic level, above the minimal inhibitory concentration (MIC). An additional administration of a corticosteroid is often needed, in order to limit the precorneal damages caused by the infection. However, repeated administration of a corticosteroid can increase intraocular pressure and thus lead to glaucoma. To overcome the disadvantages of separated and repeated instillations of two products and to avoid the side effects of dexamethasone, a soluble insert containing gentamicin sulfate and dexamethasone phosphate was developed. The new system ensures the concomitant release of the two drugs during the first 10 h of treatment, followed by an adequate concentration of gentamicin sulfate, above the MIC of 4.0 microgram ml-1, during 50 h, due to a combination of gentamicin sulfate with cellulose acetate phthalate, which reduces the solubility of gentamicin.

Nonulcerating bacterial keratitis associated with soft and rigid contact lens wear

OBJECTIVE

An unusual presentation of contact lens-related bacterial keratitis is that of epithelial nodular infiltrates and stromal inflammation without epithelial ulceration. The authors study the initial diagnosis, clinical features, causative organisms, and outcomes of corneal infections presenting in this manner.

DESIGN

The study design was a 20-month retrospective chart review.

PARTICIPANTS

Five patients with culture-proven bacterial keratitis who had predominantly nodular epithelial lesions were studied.

RESULTS

Four infections were associated with soft contact lens wear and one with rigid lens wear. All patients had largely intact epithelium; typical gray-colored epithelial nodules, some with underlying anterior stromal haze; and diffuse, fine, cellular stromal inflammation. Two patients were referred with the tentative diagnosis of Acanthamoeba infection and two as contact lens-related sterile keratitis. Epithelial cultures from three cases yielded Serratia sp., one yielded Corynebacterium, and one Streptococcus pneumoniae. All responded to antibacterial medication; final corrected visual acuity in all cases was 20/30 or better.

CONCLUSIONS

Bacterial infection associated with contact lens wear can be established within the corneal epithelium without initially producing an ulcer. A wide range of both gram-positive and gram-negative organisms can be involved. Early recognition and treatment appear to result in a favorable outcome.

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.

Acanthamoeba keratitis: risk factors and outcome

AIMS/BACKGROUND

This study was initiated to investigate risk factors for and outcome of Acanthamoeba keratitis.

METHODS

Results of treatment were studied in 22 patients (23 eyes) presenting to Bristol Eye Hospital between 1985 and February 1995. Details related to the use and disinfection of contact lenses were also obtained. An additional two patients who were seen at Bristol but mainly treated elsewhere were surveyed for contact lens related information only.

RESULTS

The incidence of Acanthamoeba keratitis rose substantially in the 1990s: three patients presented before 1990, while the remaining 21 presented between January 1990 and February 1995. Eleven patients have presented since january 1994. All of the patients in this series were contact lens wearers, 16 (67%) using daily wear disposable contact lenses. Contact lens disinfection data were available in 22 patients of whom 11 (50%) were using chlorine disinfectant. Other types of disinfection were much less common. Four patients (18%) had not used any disinfectant. During the course of the series the average diagnostic delay has fallen markedly, although in 77% of patients a diagnosis of a viral keratitis, most commonly herpes simplex, was made on first presentation. All but three of the series were treated with a combination of polyhexamethylene biguanide and propamidine isethionate. Penetrating keratoplasty was performed in 9/23 eyes (39%); in all of these eyes diagnosis was delayed for at least 6 weeks. All but one of the eyes in the series achieved a visual acuity of 6/9 or better after treatment, and 18 eyes (78%) saw 6/6 or better.

CONCLUSIONS

Most patients with Acanthamoeba keratitis can now expect a good visual result and cure by medical therapy alone is favoured by early diagnosis.

Acanthamoeba keratitis. Contact lens and noncontact lens characteristics

PURPOSE

To identify potential differences in time to diagnosis and final visual outcome between contact lens and noncontact lens users with Acanthamoeba keratitis.

BACKGROUND

Prior studies have shown early diagnosis and therapy to be related to outcome but have not analyzed differences among patients with and without contact lenses.

METHODS

A retrospective analysis of 11 consecutive cases (involving 13 eyes) of Acanthamoeba keratitis diagnosed at one institution over a 3-year period.

RESULTS

Mean time to diagnosis was significantly longer in noncontact lens users versus those who wore contact lenses (mean, 5.8 versus 3.3 weeks). Fifty percent of patients who did not wear contact lenses had a poor outcome (visual acuity worse than 20/40 or penetrating keratoplasty) versus 14% of patients who wore contact lenses.

CONCLUSION

Diagnoses were made later in patients without contact lenses, and these patients had a worse visual outcome than those with Acanthamoeba keratitis who wore contact lenses. All patients with unresponsive microbial keratitis, even those without contact lens use, should be evaluated for Acanthamoeba.

Effectiveness of specific antibiotic/steroid combinations for therapy of experimental Pseudomonas aeruginosa keratitis

Ciprofloxacin and prednisolone, but not an aminoglycoside and dexamethasone, were previously found to be effective in killing bacteria and reducing inflammation for the treatment of Pseudomonas keratitis. We investigated the therapeutic effectiveness of tobramycin/prednisolone and ciprofloxacin/dexamethasone in a rabbit model of experimental keratitis to increase our understanding of the effectiveness of antibiotic/steroid combinations. To our knowledge, this is the first analysis of the effectiveness of a combination of ciprofloxacin and dexamethasone for experimental keratitis. Two experiments were conducted. In the first experiment, 36 rabbits were divided into six groups: 1) untreated; 2) prednisolone acetate, 1.0%; 3) prednisolone phosphate, 1.0%; 4) tobramycin, 1.36%; 5) tobramycin plus prednisolone acetate; 6) tobramycin plus prednisolone phosphate. In the second experiment, 23 rabbits were divided into four groups: 1) untreated; 2) ciprofloxacin, 0.3%, plus dexamethasone alcohol, 0.1%; 3) ciprofloxacin; 4) dexamethasone alcohol. Topical antibiotic and/or steroid was given for 10 h, from 16 to 26 h postinfection, one drop every 15 min for the first hour and then every 30 min for the remaining 9 h. At 27 h postinfection, eyes were evaluated by slit lamp examination (SLE) and assayed for the presence of bacteria in terms of colony forming units (CFU) per cornea. Both prednisolone acetate and prednisolone phosphate reduced ocular inflammation (as determined by SLE), compared with no treatment (P < or = 0.036); the phosphate was more effective (P = 0.005). Tobramycin alone and in combination with prednisolone also significantly reduced SLE, compared with no treatment (P < or = 0.006). The bactericidal activity of tobramycin was not affected by either steroid formulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Herpetic Eye Disease Study. A controlled trial of topical corticosteroids for herpes simplex stromal keratitis

PURPOSE

To evaluate the efficacy of topical corticosteroids in treating herpes simplex stromal keratitis.

METHODS

The authors performed a randomized, double-masked, placebo-controlled, multicenter clinical trial of 106 patients with active herpes simplex stromal keratitis who had not received any corticosteroids for at least 10 days before study enrollment. Patients were assigned to the placebo group (n = 49) or the steroid group (topical prednisolone phosphate; n = 57); both regimens were tapered over 10 weeks. Both groups received topical trifluridine. Visual acuity assessment and slit-lamp biomicroscopy were performed weekly for 10 weeks, every other week for an additional 6 weeks or until removal from the trial, and at 6 months after randomization.

RESULTS

The time to treatment failure (defined by specific criteria as persistent or progressive stromal keratouveitis or an adverse event) was significantly longer in the steroid group compared with the placebo group. Compared with placebo, corticosteroid therapy reduced the risk of persistent or progressive stromal keratouveitis by 68%. The time from randomization to resolution of stromal keratitis and uveitis was significantly shorter in the steroid group compared with the placebo group even though both groups included patients who were removed from the study and treated with topical corticosteroids according to best medical judgment. Nineteen (33%) of the steroid-treated patients and 11 (22%) of the placebo-treated patients completed the 10 weeks of protocol therapy and had stable, noninflamed corneas after 16 weeks. At 6 months after randomization, no clinically or statistically significant differences in visual outcome or recurrent herpetic eye disease were identified between the steroid and placebo groups.

CONCLUSIONS

The topical corticosteroid regimen used in this study was significantly better than placebo in reducing persistence or progression of stromal inflammation and in shortening the duration of herpes simplex stromal keratitis. Postponing steroids during careful observation for a few weeks delayed resolution of stromal keratitis but had no detrimental effect as assessed by visual outcome at 6 months.

Pharmacokinetic considerations in the treatment of bacterial keratitis

The eye is relatively impermeable to micro-organisms and other environmental elements. However, if corneal integrity is breached by trauma, a sight-threatening bacterial infection can result. Staphylococcus aureus, Pseudomonas aeruginosa, and Streptococcus pneumoniae are the most common bacterial pathogens associated with infection of compromised corneas. Bacterial enzymes and toxins, as well as factors associated with the host immune response, can lead to tissue destruction during corneal infection. For successful therapy, an antibacterial agent must be active against the pathogen and must be able to overcome the permeability barrier of the cornea. Topical application of antibacterial agents adequately delivers drugs to the cornea and aqueous humour. However, drug concentrations at the site of infection are not always sufficient to rapidly kill infective organisms. Infections with antibiotic-resistant strains present an even greater therapeutic challenge. In addition, sterilisation of the cornea by antibacterial agents does not eliminate inflammation and corneal scarring that accompany infection. Steroidal and non-steroidal antiinflammatory agents limit corneal scarring during experimentally induced bacterial keratitis. However, although promising, concomitant use of these drugs with antibacterial agents remains controversial. Two ocular drug delivery systems that provide high and sustained concentrations of drug to ocular tissues are corneal collagen shields and transcorneal iontophoresis. The collagen shield, originally designed as a bandage lens, prolongs drug contact with the cornea. Chemotherapeutic studies of experimental bacterial keratitis demonstrate that shields hydrated with antibacterial agents reduce bacteria in the cornea as well as or better than frequent applications of fortified antibacterial drops. Transcorneal iontophoresis uses an electric current to drive charged drugs into the cornea. In experimentally induced bacterial keratitis, transcorneal iontophoresis of antibacterial agents is superior to topically administered ocular drops for reducing the numbers of bacteria in the cornea. Although both drug delivery systems appear to be well tolerated and nontoxic in animal models, clinical trials in patients are required to determine the usefulness of these drug delivery systems in clinical trials. Based on present experimental results, future therapy of bacterial keratitis will involve efficient drug delivery devices, the use of new antibacterial agents or combinations of presently available antibacterial agents, and careful use of adjuvant anti-inflammatory agents.

The changing spectrum of fungal keratitis in south Florida

PURPOSE

To review the clinical experience with fungal keratitis in south Florida over a 10-year period.

METHODS

One hundred twenty-five cases of fungal keratitis were identified in the microbiology laboratory records between January 1982 and January 1992. The medical record of each patient was reviewed.

RESULTS

The most commonly associated risk factor was trauma (44%). Fungal keratitis developed in five patients using extended wear contact lenses and one patient wearing a therapeutic bandage contact lens. Clinical features included irregular, feathery margins (62%), a dry, rough texture (47%), and satellite lesions (41%). An initial positive culture was obtained in 90% of patients, with a majority of cultures becoming positive within 48 hours. The Fusarium sp accounted for 62% of the isolates, with Fusarium oxysporum being the most commonly isolated organism. New fungal isolates include Candida parapsilosis, Aspergillus terreus, Candida tropicalis, and Trichosporon beigellii. Natamycin 5% suspension was the initial antifungal agent used for 91% of the patients, with an average duration of treatment of 38 days. Twenty-five patients were treated with oral ketoconazole for a median duration of 2 weeks, in addition to topical antifungal therapy. Thirty-four patients (27%) required a penetrating keratoplasty. Six patients had recurrence of fungal keratitis after penetrating keratoplasty.

CONCLUSIONS

Trauma, including contact lens wear, is the most commonly associated risk factor. The fungal organisms can be readily identified in culture. F. oxysporum is the most common organism, with new isolates identified. The mainstay of therapy is topical natamycin with the increasing use of imidazoles.

Prevalence of fungal corneal ulcers in northern India

Fungal corneal ulcer is common in India due to the tropical climate and a large agrarian population that is at risk. Various factors such as trauma, the injudicious use of topical antibiotics and corticosteroids are involved. Many of the age and sex-related risk factors also play a minor role. This 6-year study from Northern India revealed that fungi were detected in 61 (8.4%) out of 730 patients investigated. Direct microscopy was positive in 51 (7%) and culture in 53 (7.3%) patients. Aspergillus spp. were the most common causative agents accounting for 25 (40.1%) of the isolates, followed by Fusarium sp. with ten (16.4%), Curvularia sp. with five (8.2%), Candida albicans with five (8.2%), Acremonium sp. with four (6.6%), Paecilomyces sp. with three (4.9%), Penicillium sp. with two (3.3%), Alternaria sp. with two (3.3%), Fonsecaea pedrosoi var. cladosporium with two isolates (3.3%) and Pseudallescheria boydii, Drechslera sp. and Aureobasidium pullulans with one isolate (1.6%) each. The prevalence of fungal ulcers in males was three times higher than in females. The affected individuals had a rural background and were in the 51-60 year age group.

Non-ulcerative fungal keratitis diagnosed by posterior lamellar biopsy

We report a case of Fusarium solani keratitis which highlights the difficulties often associated with management of fungal corneal infections. This case demonstrates several unusual and interesting features: the occurrence of deep fungal pathology after superficial injury, the difficulties encountered in attempting to isolate and identify the causative organism, and the protracted course taken by an organism often noted to be rapidly destructive. These features necessitated an individual approach to therapy, employing unconventional medical and surgical techniques to achieve a satisfactory outcome.

Results of therapeutic penetrating keratoplasty

PURPOSE

To determine the anatomic and visual results of therapeutic penetrating keratoplasty (PK) and its role in the management of corneal disease.

METHODS

The authors reviewed the records of all of their patients who had undergone therapeutic PK over the past 9 years and evaluated each for the following criteria: cure of disease, graft clarity, and visual acuity. Patients were divided into seven categories: (1 and 2) bacterial and fungal keratitis, (3 and 4) herpetic keratitis, with and without inflammation, (5) acanthamoebic keratitis, (6) perforations due to keratoconjunctivitis sicca, and (7) other causes of perforation.

RESULTS

In microbial keratitis, therapeutic PK eradicated the disease in all cases. Seventy-three percent of grafts for bacterial keratitis and 60% for fungal keratitis remained clear. A higher percentage of clarity was achieved when grafts were 9.0 mm or less. Seven patients with secondary endophthalmitis were cured with a surgical approach including therapeutic PK. In herpetic keratitis with active inflammation, only 36% of grafts remained clear, and inflammation recurred in 36%. All perforations due to post-herpetic persistent epithelial defects in "quiet" eyes were grafted successfully. In patients with severe keratoconjunctivitis sicca, eyes were anatomically stabilized in 83%, but all grafts failed because of complications from ocular surface disease.

CONCLUSIONS

Therapeutic PK is valuable in the management of microbial keratitis that does not respond to antimicrobial therapy. Results are poorer for patients with herpetic keratitis, although selected patients respond to therapeutic PK when other methods of management have failed. Patients with perforations due to keratoconjunctivitis sicca have a uniformly poor prognosis for graft clarity.