Advances in the management of keratomycosis and Acanthamoeba keratitis

Diagnostic accuracy of confocal scan in detecting acanthamoeba keratitis and fungal keratitis: a systematic review and meta-analysis

PURPOSE

Acanthamoeba keratitis (AK) and fungal keratitis (FK) are two microbial keratitis that cause serious damage and, without early accurate diagnosis and treatment, may lead to blindness. In vivo corneal confocal scan, as an emerging ocular diagnostic method in comparison with microbiological smears and cultures as the gold standard, may assist in accelerating appropriate diagnosis.

OBJECTIVE

To determine the diagnostic accuracy of confocal scan for the diagnosis of AK and FK.

METHODS

Data were collected via a comprehensive literature search of PubMed, Web of Science, Cochrane Library, Embase and Scopus using keywords related to diagnostic accuracy of confocal scan in AK and FK up to October 2022. Pooled data underwent meta-analysis in terms of sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and overall diagnostic odds ratio (DOR) of confocal scan for the diagnosis of AK and FK.

RESULTS

The final 14 relevant studies were identified, including 1950 eyes. Meta-analysis in AK group revealed 94% sensitivity, 87% specificity, 89% PPV, 92% NPV, and DOR of 143.32, and in FK group disclosed 88% sensitivity, 85% specificity, 85% PPV, 88% NPV, and DOR of 75.98.

CONCLUSION

The accuracy of confocal scan for the diagnosis of AK was significantly more than that for detecting FK; despite the limitations such as limited numbers of available retrospective studies for the detection of FK, confocal scan had an acceptable performance in detecting FK eyes. The overall performance of NCS was similar with that of HRT-RCM for the detection of both types of keratitis.

Acanthamoeba keratitis and contact lens wear

Acanthamoeba keratitis is a rare but serious complication of contact lens wear that may cause severe visual loss. The clinical picture is usually characterised by severe pain, sometimes disproportionate to the signs, with an early superficial keratitis that is often misdiagnosed as herpes simplex virus (HSV) keratitis. Advanced stages of the infection are usually characterised by central corneal epithelial loss and marked stromal opacification with subsequent loss of vision. In this paper, six cases of contact lens-related Acanthamoeba keratitis that occurred in Australia and New Zealand over a three-year period are described. Three of the patients were disposable soft lens wearers, two were hybrid lens wearers and one was a rigid gas permeable lens wearer. For all six cases, the risk factors for Acanthamoeba keratitis were contact lens wear with inappropriate or ineffective lens maintenance and exposure of the contact lenses to tap or other sources of water. All six patients responded well to medical therapy that involved topical use of appropriate therapeutic agents, most commonly polyhexamethylene biguanide and propamidine isethionate, although two of the patients also subsequently underwent deep lamellar keratoplasty due to residual corneal surface irregularity and stromal scarring. Despite the significant advances that have been made in the medical therapy of Acanthamoeba keratitis over the past 10 years, prevention remains the best treatment and patients who wear contact lenses must be thoroughly educated about the proper use and care of the lenses. In particular, exposure of the contact lenses to tap water or other sources of water should be avoided.

Effectiveness and Safety of Topical Chlorhexidine and Vitamin E TPGS in the Treatment of Acanthamoeba Keratitis: A Survey on 29 Cases

This study aimed to test the effectiveness of a solution of chlorhexidine (CHX) and D-α-tocopheryl polyethylene glycol succinate (Vitamin E TPGS or TPGS) in the treatment of Acanthamoeba keratitis (AK) via a prospective, interventional case series study. Twenty-nine consecutive patients with AK were enrolled. At baseline, best-corrected visual acuity (BCVA), slit lamp examination, confocal microscopy, and polymerase chain reaction (PCR) were performed. Topical therapy with CHX 0.02% and VE-TPGS 0.2% was administered hourly/24 h for the first day, hourly in the daytime for the next three days, and finally, every two hours in the daytime up to one month. BCVA and ocular inflammation were recorded after two weeks, four weeks, and three months from baseline. Mean logMAR BCVA significantly improved at two weeks (0.78) compared to baseline (1.76), remaining stable over time (0.80 at four weeks, 0.77 at three months). Ocular inflammation improved in 14 eyes at 2 weeks, with further slow improvements in all cases. At three months, no patient had signs of corneal inflammation. The presence of corneal scars was first recorded at the two-week follow-up, with an enlargement at the four-week follow-up. At the three-month follow-up, 19 eyes still showed corneal opacities. In conclusion, the tested solution was shown to be effective for the treatment of AK. Furthermore, it might represent a good first-line treatment.

Drug Discovery against Acanthamoeba Infections: Present Knowledge and Unmet Needs

Although major strides have been made in developing and testing various anti-acanthamoebic drugs, recurrent infections, inadequate treatment outcomes, health complications, and side effects associated with the use of currently available drugs necessitate the development of more effective and safe therapeutic regimens. For any new anti-acanthamoebic drugs to be more effective, they must have either superior potency and safety or at least comparable potency and an improved safety profile compared to the existing drugs. The development of the so-called 'next-generation' anti-acanthamoebic agents to address this challenge is an active area of research. Here, we review the current status of anti-acanthamoebic drugs and discuss recent progress in identifying novel pharmacological targets and new approaches, such as drug repurposing, development of small interfering RNA (siRNA)-based therapies and testing natural products and their derivatives. Some of the discussed approaches have the potential to change the therapeutic landscape of Acanthamoeba infections.

Corticosteroid eye drop instillation aggravates the development of Acanthamoeba keratitis in rabbit corneas inoculated with Acanthamoeba and bacteria

The role of topical corticosteroids in management of Acanthamoeba keratitis (AK) remains controversial. Using a rabbit AK model, we investigated whether corticosteroid use is a risk factor of AK. Acanthamoeba (1 × 10⁵/ml) was incubated with two densities of P. aeruginosa (PA; high-PA: 1 × 10⁸/ml, low-PA: 3 × 10⁵/ml) before corneal inoculation. Rabbit corneas were inoculated with Acanthamoeba alone or Acanthamoeba plus PA and administered levofloxacin and betamethasone sodium phosphate (BSP) eye drops for 5 or 7 days. Infected rabbit eyes were evaluated for clinical score and Acanthamoeba by histological examination. Acanthamoeba alone and BSP treatment did not produce keratitis. Corneas inoculated with Acanthamoeba plus low-PA treated immediately with levofloxacin and BSP remained clear with few infiltrates. Corneas inoculated with Acanthamoeba plus low-PA treated with levofloxacin immediately and BSP 12 h later developed severe keratitis. Corneas inoculated with Acanthamoeba plus high-PA treated immediately with levofloxacin and BSP also developed severe keratitis. Acanthamoebae were detected by PAS staining in corneas inoculated with Acanthamoeba plus high-PA treated with levofloxacin and BSP. Topical corticosteroids have the potential to aggravate AK when cornea is infected by Acanthamoeba with a critical number of bacteria or when corticosteroids are given after infection has established by Acanthamoeba with small number of bacteria.

Efficient therapeutic effect of Nigella sativa aqueous extract and chitosan nanoparticles against experimentally induced Acanthamoeba keratitis

Acanthamoeba keratitis (AK) is a devastating, painful corneal infection, which may lead to loss of vision. The development of resistance and failure of the currently used drugs represent a therapeutic predicament. Thus, novel therapies with lethal effects on resistant Acanthamoeba are necessary to combat AK. In the present study, the curative effect of Nigella sativa aqueous extract (N. sativa) and chitosan nanoparticles (nCs) and both agents combined were assessed in experimentally induced AK. All inoculated corneas developed varying grades of AK. The study medications were applied on the 5th day postinoculation and were evaluated by clinical examination of the cornea and cultivation of corneal scraps. On the 10th day posttreatment, a 100% cure of AK was obtained with nCs (100 μg/ml) in grades 1 and 2 of corneal opacity as well as with N. sativa 60 mg/ml-nCs 100 μg/ml in grades 1, 2, and 3 of corneal opacity, highlighting a possible synergistic effect. On the 15th day posttreatment, a 100% cure was reached with N. sativa aqueous extract (60 mg/ml). Moreover, on the 20th day posttreatment, N. sativa (30 mg/ml) provided a cure rate of 87.5%, while nCs (50 μg/ml) as well as N. sativa 30 mg/ml-nCs 50 μg/ml yielded a cure rate of 75%; the lowest percentage of cure (25%) was obtained with chlorhexidine (0.02%), showing a non-significant difference compared to the parasite control. The clinical outcomes were in agreement with the results of corneal scrap cultivation. The results of the present study demonstrate the effectiveness of N. sativa aqueous extract and nCs (singly or combined) when used against AK, and these agents show potential for the development of new, effective, and safe therapeutic alternatives.

Altered Patterns of Fungal Keratitis at a London Ophthalmic Referral Hospital: An Eight-Year Retrospective Observational Study

PURPOSE

In previous studies of fungal keratitis (FK) from temperate countries, yeasts were the predominant isolates, with ocular surface disease (OSD) being the leading risk factor. Since the 2005-2006 outbreak of contact lens (CL)-associated Fusarium keratitis, there may have been a rise in CL-associated filamentary FK in the United Kingdom. This retrospective case series investigated the patterns of FK from 2007 to 2014. We compared these to 1994-2006 data from the same hospital.

DESIGN

Retrospective observational study.

METHODS

All cases of FK presenting to Moorfields Eye Hospital between 2007 and 2014 were identified. The definition of FK was either a fungal organism isolated by culture or fungal structures identified by light microscopy (LM) of scrape material, histopathology, or in vivo corneal confocal microscopy (IVCM). Main outcome measure was cases of FK per year.

RESULTS

A total of 112 patients had confirmed FK. Median age was 47.2 years. Between 2007 and 2014, there was an increase in annual numbers of FK (Poisson regression, P = .0001). FK was confirmed using various modalities: 79 (70.5%) by positive culture, 16 (14.3%) by LM, and 61 (54.5%) by IVCM. Seventy-eight patients (69.6%) were diagnosed with filamentary fungus alone, 28 (25%) with yeast alone, and 6 (5.4%) with mixed filamentary and yeast infections. This represents an increase in the proportion of filamentary fungal infections from the pre-2007 data. Filamentary fungal and yeast infections were associated with CL use and OSD, respectively.

CONCLUSIONS

The number of FK cases has increased. This increase is due to CL-associated filamentary FK. Clinicians should be aware of these changes, which warrant epidemiologic investigations to identify modifiable risk factors.

The Impact of Topical Corticosteroids Used in Conjunction with Antiamoebic Therapy on the Outcome of Acanthamoeba Keratitis

PURPOSE

To examine the impact of topical corticosteroid use after the start of antiamoebic therapy (AAT) on the outcomes of Acanthamoeba keratitis (AK) therapy.

DESIGN

Cohort study.

PARTICIPANTS

A total of 196 patients diagnosed with AK at Moorfields Eye Hospital, London, between January 1991 and April 2012. In 13 patients with bilateral AK, 1 eye was randomly excluded from analysis.

METHODS

Patient demographics and clinical examination findings were collected both at the start of AAT and subsequently at the time that topical corticosteroid therapy was initiated. Preliminary a priori investigations were used to identify effect modifiers/confounders and extreme associations requiring consideration in multivariate regression modeling. A multivariable logistic model, optimized for assessment of corticosteroid use after the start of AAT, was used to estimate the odds ratios (ORs) of a suboptimal outcome.

MAIN OUTCOME MEASURES

Suboptimal outcome was defined as final visual acuity ≤20/80, corneal perforation, or the need for keratoplasty.

RESULTS

In multivariable analysis, restricted to 129 eyes (1 eye per patient) free of scleritis and hypopyon at the start of AAT, topical corticosteroids were not associated with worse outcomes (OR, 1.08; 95% confidence interval [CI], 0.39-3.03), even when corticosteroids had been used before the start of AAT. Risk factors significantly associated with worse outcomes were topical corticosteroid use before the start of AAT (OR, 3.85; 95% CI, 1.35-11.03), a corneal ring infiltrate (together with at least 1 other feature of AK) present at the start of AAT (OR, 5.89; 95% CI, 1.17-29.67), and age ≥33 years at the start of AAT (OR, 4.02; 95% CI, 1.46-11.06).

CONCLUSIONS

Many corneal specialists currently are uncertain about the risk benefit associated with the use of topical corticosteroids for the management of inflammatory complications of AK. The evidence from this study gives clinicians and patients reassurance that the potential benefits of topical corticosteroid therapy, for treating pain and discomfort, are not associated with worse outcomes when initiated after starting modern AAT. Other potential benefits, in terms of resolution of inflammatory complications, will not be demonstrated without a carefully designed randomized clinical trial.

Toll-like receptor-associated keratitis and strategies for its management

Keratitis is an inflammatory condition, characterized by involvement of corneal tissues. Most recurrent challenge of keratitis is infection. Bacteria, virus, fungus and parasitic organism have potential to cause infection. TLR are an important class of protein which has a major role in innate immune response to combat with pathogens. In last past years, extensive research efforts have provided considerable abundance information regarding the role of TLR in various types of keratitis. This paper focuses to review the recent literature illustrating amoebic, bacterial, fungal and viral keratitis associated with Toll-like receptor molecules and summarize existing thoughts on pathogenesis and treatment besides future probabilities for prevention against TLR-associated keratitis.

Corneal infections in the 21st century

Ninety years ago, the first issue of the Postgraduate Medical Journal published a review of an article written by Mr Robert Lindsay-Rea, a consultant ophthalmic surgeon in the Western Ophthalmic Hospital and an oculist in the West End Hospital for Nervous Diseases, entitled "A preliminary report on the treatment of keratitis". Today, microbial keratitis remains an important cause of avoidable visual impairment in the world. The aetiology of microbial keratitis has changed greatly over the past century due to the discovery of antibiotics, improvement in sanitation and education, the rising trend of contact lens wear and increased air travel. Significant advances have also been made in our understanding and management of this important disorder. This article highlights some of these changes and discusses the current management and research.

Effects of Lamellar Keratectomy and Intrastromal Injection of 0.2% Fluconazole on Fungal Keratitis

Purpose. To evaluate effects of lamellar keratectomy and intrastromal injection of 0.2% fluconazole (LKIIF) on fungal keratitis. Methods. Data for 54 eyes of consecutive patients with fungal keratitis treated with LKIIF were retrospectively analyzed. The lesions in these eyes did not heal or were aggravated after antifungal chemotherapy for 7 days. The maximum lesion diameters were ≤5 mm and maximum depth was not more than half of full corneal thickness. Cases were followed up for at least 90 days. Results. Forty-six eyes were cured (85.2%). The wound healing times were 3–16 days and were less than 7 days in 28 cases (51.9%). In cured eyes, uncorrected visual acuity (UCVA) and best-corrected visual acuity (BCVA) were both 20/250–20/20. The UCVA improved in 38 eyes and was unchanged in seven eyes. BCVA improved in 44 eyes and was unchanged in two eyes. When followed up for more than 90 days, 89% (41 of 46 eyes) showed improvement in UCVA and 11% were unchanged. Regarding BCVA, 98% improved and one eye was unchanged. No other complications were observed except neovascularization in one eye and thinner corneas. Conclusions. LKIIF was quick and effective for small fungal keratitis confined to half of the corneal thickness.

Chlorhexidine Monotherapy with Adjunctive Topical Corticosteroids for Acanthamoeba Keratitis

PURPOSE

To assess the efficacy of chlorhexidine monotherapy for Acanthamoeba keratitis, and to determine the therapeutic outcomes of concomitant topical corticosteroids.

METHODS

In this prospective interventional case series, 31 eyes of 31 patients with Acanthamoeba keratitis (AK) were treated with chlorhexidine 0.02% as monotherapy, from April 2010 to April 2011. The diagnosis of AK was made based on clinical manifestations and positive confocal microscopic (confoscan 3.4, Nidek Co. Ltd., Gamagori, Japan) results. We report the percentage of a favorable clinical response within two weeks of initiating treatment, worsening of the infection while receiving chlorhexidine, recovery of visual acuity (VA), duration of treatment with chlorhexidine and corticosteroids, necessity for addition of other anti-Acanthamoeba agents, presence of corneal scar at the end of the treatment, and need for penetrating keratoplasty (PK).

RESULTS

Two weeks after initiation of chlorhexidine, improvement in signs and symptoms was observed in 26 (83.9%) patients but 3 eyes required the addition of propamidine. After initial improvement in one patient, the infection worsened, necessitating the addition of Polyhexamethylene Biguanide (PHMB) and propamidine. A total of 26 (83.9%) patients received topical corticosteroids with mean duration of 65.8 ± 45.1 days. In 22 (71%) eyes, final visual acuity was ≥0.80. Improved VA occurred in 29 eyes (93.5%). Optical PK was considered in 3 (9.7%) eyes and a corneal scar developed in 8 (25.8%) eyes.

CONCLUSION

Chlorhexidine is effective for monotherapy in AK and could be a good choice for initiating treatment. After the initial response to anti-Acanthamoeba agents, corticosteroids can be used as adjunctive therapy depending on the clinical condition.

The impact of topical corticosteroid use before diagnosis on the outcome of Acanthamoeba keratitis

OBJECTIVE

To examine the impact of topical corticosteroid use before the diagnosis of Acanthamoeba keratitis (AK) on final visual outcomes and to determine the prognostic factors predicting poorer outcomes.

DESIGN

Cohort study.

PARTICIPANTS

A total of 209 eyes of 196 patients with retrievable medical records, diagnosed with AK at Moorfields Eye Hospital, London, between January 1991 and April 2012. One eye was randomly excluded from analysis in the 13 cases of bilateral AK.

METHODS

Patient demographic, initial clinical examination findings, and management details were collected. The outcomes of patients treated with topical corticosteroids before diagnosis of AK were compared with those not treated with topical corticosteroids before diagnosis. A multivariable logistic model, optimized for prior corticosteroid use, was used to derive the odds ratios (ORs) of a suboptimal visual outcome.

MAIN OUTCOME MEASURES

Suboptimal visual outcome was defined as final visual acuity (VA) ≤ 20/80, corneal perforation, or need for keratoplasty.

RESULTS

Acanthamoeba keratitis was diagnosed on microbiological culture in 94 eyes (48.0%), on histopathologic examination in 27 eyes (13.8%), on confocal microscopy in 38 eyes (19.4%), and on the basis of a typical clinical course and response to treatment in 37 eyes (18.9%). Final VA and prior corticosteroid use data were available for 174 eyes (88.8%). In multivariable analysis, corticosteroid use before diagnosis was associated with suboptimal visual outcome (OR, 3.90; 95% confidence interval [CI], 1.78-8.55), as were disease stage 3 at presentation (OR, 5.62; 95% CI, 1.59-19.80) and older age (60+ years) at diagnosis (OR, 8.97; 95% CI, 2.13-37.79).

CONCLUSIONS

Corticosteroid use before diagnosis of AK is highly predictive of a poorer visual outcome. This is largely due to the initial misdiagnosis of AK as herpetic keratitis. It is important to include AK in the differential diagnosis of keratitis in all contact lens users with keratitis, particularly before making a diagnosis of herpes keratitis and before the use of topical corticosteroids in the therapy of any indolent keratitis.

Practice patterns and opinions in the treatment of acanthamoeba keratitis

PURPOSE

Management of acanthamoeba keratitis remains challenging for ophthalmologists. We conducted a survey of members of The Cornea Society to elicit expert opinions on the diagnosis and treatment of acanthamoeba keratitis.

METHODS

An online survey was sent to all subscribers of The Cornea Society via the kera-net listserv. Descriptive statistics were performed.

RESULTS

Eighty-two participants completed the online survey. Of the 82 respondents, 76.8% included the combination of clinical examination and culture in their diagnostic strategy and 43.9% used confocal microscopy. Most respondents (97.6%) had used combination therapy with multiple agents to treat acanthamoeba keratitis at some point in the past, whereas a smaller proportion (47.6%) had ever used monotherapy. Respondents most commonly chose polyhexamethylene biguanide as the ideal choice for monotherapy (51.4%), and dual therapy with a biguanide and diamidine as the ideal choice for combination therapy (37.5%). The majority of respondents (62.2%) reported using topical corticosteroids at least some of the time for acanthamoeba keratitis. Keratoplasty was an option considered by most respondents (75.6%), although most (85.5%) would only perform surgery after medical treatment failure.

CONCLUSIONS

There was a wide range of current practice patterns for the diagnosis and treatment of acanthamoeba keratitis. The lack of sufficiently powered comparative effectiveness studies and clinical trials makes evidence-based decision-making for this disease difficult.

Integrated assessment of mangrove sediments in the Camamu Bay (Bahia, Brazil)

Camamu Bay, an Environmentally Protected Area, may be affected by the pressures of tourism and oil exploration in the adjacent continental platform. The current quality of the mangrove sediments was evaluated by porewater bioassays using embryos of Crassostrea rhizophorae and by an analysis of benthic macrofauna and its relationships with organic compounds, trace metals and bioavailability. Porewater toxicity varied from low to moderate in the majority of the samples, and polychaetes dominated the benthos. The Grande Island sampling station (Station 1) presented more sandy sediments, differentiated macrobenthic assemblages and the highest metal concentrations in relation to other stations and guideline values, and it was the only station that indicated a possible bioavailability of metals. The origin of the metals (mainly barium) is most likely associated with the barite ore deposits located in the Grande and Pequena islands. These results may be useful for future assessment of the impact of oil exploration in the coastal region.

Fungal keratitis

CLINICAL QUESTION

What is the most appropriate management of fungal keratitis?

RESULTS

Traditionally, topical Natamycin is the most commonly used medication for filamentous fungi while Amphotericin B is most commonly used for yeast. Voriconazole is rapidly becoming the drug of choice for all fungal keratitis because of its wide spectrum of coverage and increased penetration into the cornea.

IMPLEMENTATION

Repeated debridement of the ulcer is recommended for the penetration of topical medications. While small, peripheral ulcers may be treated in the community, larger or central ulcers, especially if associated with signs suggestive of anterior chamber penetration should be referred to a tertiary center. Prolonged therapy for approximately four weeks is usually necessary.

Surgical outcomes in cases of contact lens-related Fusarium keratitis

OBJECTIVES

To examine seven cases of contact lens-related Fusarium keratitis that resulted in therapeutic penetrating keratoplasty, to investigate which factors were associated with favorable versus poor graft outcome in this population.

METHODS

Seven patients who underwent corneal transplant after contact lens-related, culture-proven Fusarium keratitis were identified through a retrospective chart review. The cases occurred between September 2005 and January 2006 at the University of Medicine and Dentistry of New Jersey and Wills Eye Hospital. All seven patients had used Bausch and Lomb's ReNu with MoistureLoc. The outcomes studied were graft status, infection recurrence, and 6-month postoperative visual acuity.

RESULTS

The rejection rate was 57.1% and the recurrence rate was 28.6% in this study. No eyes were lost to fungal endophthalmitis. In this population, larger ulcer size and a greater total number of medical agents used before and after penetrating keratoplasty were significantly associated with poor outcomes, namely graft rejection and poor visual acuity. In addition, it was noted that the patients who suffered recurrence of infection had both a larger median graft size and a longer median duration of postoperative antifungal use although these results did not reach statistical significance.

CONCLUSIONS

Larger ulcer size, larger graft size, a greater number of medical agents used, and a longer duration of postoperative antifungal therapy may be useful parameters in predicting surgical outcomes in patients with fungal keratitis. Further research is needed to validate our results and to elucidate the mechanisms behind graft rejection in the setting of fungal keratitis.

Medical treatment for combined Fusarium and Acanthamoeba keratitis

PURPOSE

Acanthamoeba and fungal keratitis are rare ocular infections. We report cases of combined Fusarium and Acanthamoeba keratitis and the clinical course of medical treatment.

METHODS

We reviewed the medical records of patients treated for culture-proven Acanthamoeba keratitis at a referral centre, during 2001-2006.

RESULTS

Eleven consecutive patients were treated for culture-proven Acanthamoeba keratitis during the 5 years, two of whom had combined fungal infections. A 29-year-old man presented with ground-glass corneal oedema and epitheliopathy caused by contact lens use. The other patient, a 7-year-old girl, had eye trauma that led to a feathery corneal infiltrate. Both cases were treated with topical 0.02% polyhexamethylene biguanide (PHMB), 0.1% propamidine, 1% clotrimazole and 5% natamycin. Therapeutic keratoplasty was not required in either case.

CONCLUSIONS

Timely identification of the pathogen, with repeated culture and smear if necessary, as well as adequate dosage to prevent recurrence is highly recommended in order to preclude the need for therapeutic penetrating keratoplasty.

Fungal keratitis in London: microbiological and clinical evaluation

PURPOSE

To review cases of culture-positive fungal keratitis seen at Moorfields Eye Hospital over a 13-year period to January 2007.

METHODS

Isolates were identified retrospectively from laboratory reports. The clinical records were reviewed. The fungal type, risk factors for infection, in vitro sensitivity, and clinical outcome were recorded.

RESULTS

There were 66 isolates from 65 patients (men, 53.8%). Forty (60.6%) of the isolates were subspecies of Candida. The average interval from the onset of keratitis to confirmation of fungal infection was 3.4 weeks (median, 1.0 week; range, 0-16 weeks). Prior ocular surface disease (OSD) or a penetrating keratoplasty (PK) was present in 38 (97.4%) patients with Candida infection, and 29 (74.4%) patients with Candida infection were using topical steroid at the time of diagnosis. The principal risk factors for filamentary fungal infection were trauma (8 cases, 30.8%) or cosmetic contact lens wear (8 cases, 30.8%), with OSD or a prior PK each present in 5 (19.2%) cases. The difference in the proportions of risk factors between the 2 fungal groups was statistically significant (P < 0.000). The visual outcome was similar between groups, and at final review, 27 (41.5%) eyes had a visual acuity of < or = 1/60 and 3 (4.6%) eyes were eviscerated. In vitro sensitivity testing showed full or part sensitivity in 100% of 55 isolates tested against econazole, 87.9% of 58 isolates tested against amphotericin, 75% of 40 isolates tested against itraconazole, and 100% of 20 isolates tested against voriconazole.

CONCLUSIONS

Candida was the principal isolate, usually from eyes with OSD or a prior PK treated with topical steroids.

Surgical therapies for Acanthamoeba keratitis by phototherapeutic keratectomy and deep lamellar keratoplasty

PURPOSE

To report the efficacy of phototherapeutic keratectomy (PTK) and deep lamellar keratoplasty (DLKP) in the treatment of Acanthamoeba keratitis.

METHODS

Two patients with delayed diagnosis of Acanthamoeba keratitis failed to respond to multiple systemic and topic antiamoebic agents supplemented by twice-weekly corneal scraping. Three weeks into such therapy, one developed a ring-shaped subepithelial infiltration and PTK was performed. The other was treated with DLKP for progressive keratitis that had invaded the midstromal layer after 50 days of medical therapy.

RESULTS

Improvements were observed immediately after the operations and medical therapy was gradually discontinued. Best-corrected visual acuity improved to 20/20 for both patients.

CONCLUSIONS

PTK and DLKP were found to be effective surgical procedures, especially for advanced Acanthamoeba keratitis that fails to respond to medical therapy and corneal debridement.

Prescrire les collyres antifongiques et antiamibiens

The prognosis of fungal and acanthamoeba keratitis depends on early diagnosis and treatment. Keratomycosis treatment requires antifungal eye drops such as polyene, triazoles, or echinocandins, whereas acanthamoeba keratitis therapy is based on biguanide and diamidine agents. The aim of this paper is to review the antifungal and antiamoebicide eye drops that are currently available in ophthalmology.

Diagnosis and management of Acanthamoeba keratitis

PURPOSE OF REVIEW

This paper reviews the literature generated on Acanthamoeba keratitis since 1998.

RECENT FINDINGS

Acanthamoeba infections may be on the rise. Contact lenses are the biggest risk factor for their development. Silicone hydrogel lenses are increasingly prescribed and may be 'more sticky' to Acanthamoeba organisms. Orthokeratology for the treatment of myopia has been associated with many new cases of Acanthamoeba keratitis. Daily disposable contact lenses are the safest form of soft contact lens. Patients continue to be misdiagnosed as having herpetic keratitis. Impression cytology and confocal microscopy are newer diagnostic modalities. Topical polyhexamethylene biguanide, chlorhexidine and propamidine are the mainstay of medical therapy. Amniotic membrane may be used for cases of persistent epithelial defect and to control inflammation. Penetrating keratoplasty in a medically treated eye affords a good chance of positive outcome.

SUMMARY

Acanthamoeba keratitis continues to be a difficult infection to diagnose and manage. The frequency of these infections may be on the rise, most commonly associated with frequent replacement soft contact lenses. The best chance for a good outcome is based on early diagnosis, so it is important for ophthalmologists consider it in patients, especially in the contact lens wearer with suspected herpes simplex keratitis.

Amniotic Membrane Transplantation for Persistent Corneal Ulcers and Perforations in Acute Fungal Keratitis

PURPOSE

To report the therapeutic effect and complications of amniotic membrane transplantation (AMT) in acute fungal keratitis.

METHODS

Diagnosis of fungal keratitis was confirmed by cultures in 23 eyes of 23 patients. The indications to perform AMT were to promote reepithelialization in non-healing ulcers or to prevent corneal perforation. Antifungal agents were administered throughout the whole course of hospitalization. Repeated cultures were performed immediately before AMT. The main outcome measurements were epithelial healing rate, necessity of therapeutic penetrating keratoplasty (TPK), and persistence of infection.

RESULTS

During a mean follow-up time of 20.6 months +/- 23.22 (6-65 months) AMT was performed during the active phase of the keratitis (fungal culture was still positive) in 16 patients (69.6%), and during the inactive phase (fungal culture negative) in 7 patients (30.4%). Single-layer AMT was performed in 17 patients, and double-layer AMT was performed in 6 patients with corneal perforation and anterior chamber collapse. Complete epithelialization was observed in 12 patients (75%) in the active group and in 7 patients (100%) in the inactive group. Treatment failure requiring TPK was experienced in 4 patients (25%) in the active group. Persistent fungal keratitis was noted in 2 patients (8.7%) in that group. The final visual acuity improved in 17 cases, worsened in 2 cases, and remained unchanged in 4 cases. Twelve of the 23 eyes (52.2%) in this study preserved useful vision (20/400 and better) with or without subsequent surgeries.

CONCLUSION

AMT is effective in promoting epithelialization and preventing corneal perforations in acute fungal keratitis, and there is no risk of rejection. However, the risk of persistent or recurrent infection necessitates continued antifungal treatment and patient monitoring.

Potential use of (1,3)-beta-D-glucan as target of diagnosis and treatment of keratomycosis

PURPOSE

Major problems in the management of keratomycosis stem from the difficulty of its diagnosis and limited choice of antifungal agents. In the present paper we propose a new method of detecting (1,3)-beta-D-glucan, one of the major components of fungal cell wall, in tears from an animal model of keratomycosis. In addition, we investigated the efficacy of topical application of micafungin, a new antifungal agent that inhibits the activity of (1,3)-beta-D-glucan synthase in this animal model.

METHOD

Candida albicans (5 x 10(5) organisms) was inoculated into the corneal stroma of 20 New Zealand White rabbits. The animals were randomly assigned to two groups and treated with subconjunctival injection of 0.5 mL of saline or 0.1% micafungin every day for 3 weeks. The clinical course of keratomycosis in both groups was compared. Before and 3 weeks after the injection of saline or micafungin, 5 microL of tears in each eye were collected by capillary tube. The concentration of (1,3)-beta-D-glucan was quantitatively measured by modified Limulus test.

RESULTS

The concentration of (1,3)-beta-D-glucan was significantly higher in keratomycosis model animals than in controls (mean +/- SD, 17.4 +/- 9.4 pg/mL and 2.8 +/- 1.8 pg/mL, respectively) at 21 days after treatment. Subconjunctival injection of micafungin had no significant effect on ocular lesions of keratomycosis until 9 days, after which ocular lesions significantly improved. Subconjunctival application of micafungin decreased the concentration of (1,3)-beta-D-glucan in tears to 4.9 +/- 3.0 pg/mL at 21 days after treatment.

CONCLUSIONS

Increased levels of (1,3)-beta-D-glucan in tears were detected in this model of keratomycosis. Measuring the concentration of (1,3)-beta-D-glucan in tears may be a reliable noninvasive method for the diagnosis of keratomycosis. Topical application of micafungin was effective in the treatment of keratomycosis.

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.

Candida parapsilosis keratitis

PURPOSE

To present clinical, microbiologic, and histopathologic features of keratitis due to Candida parapsilosis.

METHODS

Clinicomicrobiologic evaluation of four patients (four eyes) with culture-proven C. parapsilosis keratitis. The patients were evaluated for symptoms, visual acuity, clinical observations, microbiologic examination of corneal scrapings, and pathologic examination of corneal buttons.

RESULTS

Three cases were observed after penetrating keratoplasty, and one case occurred after inhalation of corticosteroids. Clinical presentation of C. parapsilosis keratitis showed a great diversity. There was one case of crystalline keratopathy and three cases of suppurative corneal infiltrate. Histopathology of corneal buttons showed interlamellar accumulations of yeast. Medical treatment included topical amphotericin B and systemic triazoles. Penetrating keratoplasty was required in three patients.

CONCLUSION

Risk factors for C. parapsilosis keratitis may include corticosteroid use and prior corneal transplantation. The prognosis of C. parapsilosis keratitis with antifungal and surgical therapy may vary from good visual outcome to intraocular extension with phthisis bulbi.

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.

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.