The qualitative evaluation of the pharmacokinetics of subconjunctivally injected antifungal agents in rabbits

Efficacy Profile of Intracameral Amphotericin B. The Often Forgotten Step

PURPOSE

The objectives of this study were to assess visual and structural outcomes in mycotic keratitis after conventional treatment (topical and systemic antifungals) and intracameral amphotericin B (ICAMB), and to evaluate any complications.

DESIGN

This was a prospective, nonrandomized, nonblinded interventional study.

METHODS

This study was conducted on 104 eyes of 104 patients with fungal corneal ulcers. Patients were categorized into 2 groups: group A, who received conventional topical and systemic antifungal medications, and group B, who received ICAMB in the dose of 5 to 10 μg in 1 mL of 5% dextrose. Response to treatment was evaluated. Results of the 2 groups were compared with appropriate statistical indices.

RESULTS

The mean final visual acuity in patients in group B receiving ICAMB was 1.22 ± 0.31 logMAR units. The improvement in mean visual acuity was 1.40 ± 0.2 logMAR units. In group A, mean visual outcome was 1.25 ± 0.73 logMAR units. There was an improvement by 0.55 ± 0.30 logMAR units. Healing with varying degrees of opacification occurred in a significant number of patients (81.48%) treated with ICAMB as compared with conventional treatment (Z = 2.24, P < 0.05). Complications, such as sloughing, occurred in significantly fewer patients treated with ICAMB as compared with conventional treatment (Z = 2.29, P < 0.05).

CONCLUSIONS

In cases of keratomycosis where response to local and systemic antifungal treatment is not evident after 7 days, ICAMB can be safely administered to prevent the progression of ulcers and the development of complications.

Comparison of Micafungin and Fluconazole for Experimental Candida Keratitis in Rabbits

PURPOSE

To evaluate the efficacy of subconjunctival injection of micafungin in the treatment of experimental Candida albicans keratitis in rabbits compared with fluconazole.

METHODS

In 1 eye of 24 New Zealand white rabbits, C. albicans (5 x 10 yeast cells) was inoculated in the corneal stroma. The animals were randomly assigned to 3 groups and received subconjunctival injection of 0.5 mL of 0.1% micafungin, 0.2% fluconazole, or physiologic saline once a day for 3 weeks. The eyes were examined slit-lamp biomicroscopically and histopathologically. The clinical course of fungal keratitis was compared among the 3 groups. In another 36 rabbits, a microbiological examination was performed using a quantitative isolate recovery technique, and the numbers of colony-forming units were compared among groups.

RESULTS

The clinical scores were significantly lower in the micafungin group than in the other 2 groups throughout the study period (P < 0.0001 approximately P = 0.0027, Bonferroni multiple comparison). The fluconazole group showed significantly lower clinical scores than the saline group on day 18 (P = 0.0343). At the end of the study period, there were significant differences between the saline and micafungin groups (P < 0.0001), the saline and fluconazole groups (P = 0.0072), and the fluconazole and micafungin groups (P = 0.0013). Histopathologically, similar results were obtained. Moreover, the results of the microbiological examination nearly matched the clinical and histopathologic findings.

CONCLUSIONS

Subconjunctival administration of micafungin was effective in the treatment of experimental Candida keratitis. Local application of micafungin to the eye would be a feasible treatment option for clinical fungal keratitis.

Severe fungal keratitis treated with subconjunctival fluconazole

PURPOSE

To assess the efficacy and safety of subconjunctival fluconazole treatment as an alternative therapy for severe fungal keratitis refractory to the conventional antifungal medical treatment.

DESIGN

Prospective, interventional case series.

METHODS

This study included 13 eyes of 13 patients (mean age 49.6 years, range 28 to 75) with severe fungal keratitis that did not respond to initial therapy with topical and intravenous fluconazole plus oral itraconazole. All patients were injected with subconjunctival fluconazole 2%, up to 1.0 mL twice daily, for at least 5 days. If necessary, therapy was continued once daily for a maximum of 14 days after 5 days of injections.

RESULTS

Six eyes were successfully treated after 5 days of subconjunctival injections of fluconazole. Seven patients required repeated injections for more than 5 days, but one of them finally underwent evisceration. The final visual acuity depended on the location of the remaining scar; in four cases, corneal transplantation was necessary. Neither local nor systemic toxic side effects were observed.

CONCLUSION

Subconjunctival fluconazole could be effective for treatment of severe fungal keratitis and could be very useful to avoid surgical intervention at an acute stage of this infection. Although the efficacy of the various doses cannot be determined from this series, the dose used in this study seems to be safe and effective for fungal corneal ulcer with hypopyon.

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.

Intracameral amphotericin B: initial experience in severe keratomycosis

PURPOSE

Fungal keratitis is a significant cause of ocular morbidity in India. The most commonly implicated fungi are Aspergillus spp. Patients often present with hypopyon, which usually contains fungal elements. The treatment is difficult owing to poor intraocular penetration of most available antifungal agents. This study evaluated the results of intracameral injection of amphotericin B in natamycin resistant cases of severe keratomycosis.

METHODS

Three patients of culture proven Aspergillus flavus corneal ulcer with hypopyon not responding to topical natamycin 5%, amphotericin B 0.15%, and oral itraconazole were administered intracameral amphotericin B. The first case received 7.5 microg in 0.1 mL followed by two subsequent injections of 10 microg in 0.1 mL each, the second case received two injections of 10 microg in 0.1 mL, and the third patient received a single dose of 10 microg in 0.1 mL. Culture of the aqueous sample also grew A. flavus in all three cases.

RESULTS

All three cases responded favorably, with the ulcer and hypopyon clearing completely. There was no clinical evidence of corneal or lenticular toxicity in any patient.

CONCLUSIONS

Intracameral amphotericin B may be a useful modality in the treatment of severe keratomycosis not responding to topical natamycin. It ensures adequate drug delivery into the anterior chamber and may be especially useful to avoid surgical intervention in the acute stage of the disease.

Keratomycosis after cataract surgery

PURPOSE

To evaluate cases and results of keratomycosis that developed after cataract surgery.

SETTING

Hospital de Guipúzcoa, San Sebastián, Spain.

METHODS

This retrospective study comprised 8 patients who developed keratomycosis soon after cataract surgery.

RESULTS

Culture analysis revealed 7 cases of Aspergillus fumigatus and 1 of Aspergillus flavus. After medical treatment with antifungal agents, 6 cases resolved and 2 required evisceration.

CONCLUSIONS

The presence of fungi in corneal ulcers that develop after cataract surgery should be considered. Initiation of early treatment determines the prognosis. Among the therapeutic options, collagen shields soaked in amphotericin B may be effective.

Advances in the management of keratomycosis and Acanthamoeba keratitis

PURPOSE

In the late 1960s, the management of fungal keratitis was a serious unresolved problem. Little was known of the epidemiology of the disease, and there were no antifungal agents formulated for use in the eye.

METHODS

A thorough review of the literature was done back to 1969 on clinical reports and experimental studies for keratomycosis and Acanthamoeba keratitis.

RESULTS

Since 1969, through basic and clinical research, the epidemiology of the disease worldwide is better understood. One new topical antifungal agent, natamycin, with efficacy against filamentous fungi has been developed and the pharmacokinetics of topically applied antifungal drops have been explored. Progress has been slow but the prognosis for keratomycosis has immeasurably improved over the period. Acanthamoeba was first recognized as an ocular pathogen in 1973 and was the cause of an epidemic in the 1980s caused by contaminated contact lens, although other risk factors were also identified. At the onset of the epidemic, there was no known treatment. but as a result of intense research efforts, within a few years a well-defined therapeutic approach had been developed that had a significant impact on the prognosis for this initially devastating infection. For both infections, the role of corticosteroids for controlling the inflammation remains controversial, but the place for keratoplasty is now well defined.

CONCLUSIONS

Although there has been steady progress in the management of both infections, continued research is the way to define more effective medical and surgical therapy.