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Abstract
Aim To evaluate the efficacy of intrastromal voriconazole, as a modality of treatment for management of recalcitrant fungal keratitis.
Methods Twelve patients of smear and/or culture positive fungal keratitis not responding to topical and systemic antifungal therapy were treated with additional intrastromal voriconazole therapy. Patients were given one or more intrastromal injection of voriconazole (50 μg in 0.1 ml) at the junction of clear cornea and infiltrates, using a 30-gauge needle in five quadrants to form a barrage around the ulcer. All patients continued to receive topical and systemic antifungal therapy.
Results The mean age of the patients was 47.58±15.13 years, and the mean time to presentation at the centre was 37.58±10.54 days. Organisms isolated were Aspergillus species (n=8), Fusarium species (n=3) and Curvularia (n=1). Of 12 eyes, 10 eyes healed with scar formation, and the mean resolution time was 39.75±7.62 days. Two corneas perforated and required therapeutic penetrating keratoplasty. The best-corrected visual acuity was less than 20/1200 in all patients at the time of presentation, which improved to better than 20/400 in 10 eyes and 20/40 in eyes that underwent penetrating keratoplasty at the end of 24.75±2.14 weeks' follow-up.
Conclusion Intrastromal injection of voriconazole may be used as a modality of treatment for managing cases of recalcitrant fungal keratitis.
- Cornea
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Introduction
Fungal keratitis accounts for nearly 50% of all cases of infectious keratitis in developing countries and has a poor prognosis compared with bacterial keratitis.1 2 Currently available topical antifungal drugs have limitations such as poor penetration into the eye, limited spectrum of activity and surface toxicity.3–5 Surgical intervention in the form of therapeutic keratoplasty is required more often in cases of fungal keratitis, compared with bacterial keratitis, indicating a poor response to treatment with antifungal agents.2 6
A less invasive surgical modality of use of intrastromal amphotericin B and voriconazole for cases of deep-seated fungal keratitis, non-responsive to topical and oral antifungal agents have been described in anecdotal reports.7–9 Herein, we report the results of using intrastromal voriconazole in 12 eyes with deep recalcitrant fungal keratitis non-responsive to topical and oral voriconazole therapy.
Methods
Twelve eyes of 12 patients, with microbiologically proven fungal corneal ulcer which did not respond to topical and oral voriconazole, were treated with intrastromal injections of voriconazole. The study was conducted in accordance with the Declaration of Helsinki. Informed consent was obtained from all subjects. The study was approved by the institutional review board. The diagnosis of fungal infection was made on the basis of clinical evaluation, positive smear and/or cultures of the fungus.
Inclusion criteria
Patients with microbial keratitis and proven presence of fungal organism on smear and/or culture, non-responsive on 4 weeks of topical natamycin (5%) and 2 weeks of topical voriconazole (1%) and oral voriconazole (200 mg twice daily) therapy, were included.
Exclusion criteria
Cases that had some involvement of adjacent sclera, impending or frank corneal perforation, presence of descemetocele and concomitant endophthalmitis were excluded from the study.
At the initial presentation, each patient underwent a detailed evaluation that included clinical history, recording of visual acuity and slit-lamp biomicroscopy. The parameters evaluated were size of the ulcer, size of the infiltrate and height of the hypopyon if present. All patients had deep-seated corneal infiltrates with or without hypopyon. The depth of corneal involvement in all these cases extended up to or deeper than midstromal level. Corneal scrapings were obtained under topical anaesthesia (0.5% proparacaine hydrochloride) and were sent for microbiological investigation including a potassium hydroxide (KOH) wet-mount preparation, Gram smear and cultures on blood agar, chocolate agar and Sabouraud dextrose agar. Antifungal therapy was started as soon as fungus was identified by KOH wet-mount preparation and/or Gram smear along with moxifloxacin hydrochloride eye-drops (0.5%) four times a day and topical homatropine hydrobromide (2%) three times a day.
The ulcer was defined was defined as not having improved if there was no change in the size of the ulcer or the infiltrates, and defined as having worsened if there was an increase in size or depth of ulcer/infiltrate by 20% or perforation.
Drug schedule for the antifungal agent
The drug schedule which was followed during the study period is as follows. For the first 2 weeks, topical natamycin sulfate (5%) was instilled every 2 h. If there was no improvement or response to therapy in 14 days or if the infection showed signs of worsening, hourly topical voriconazole 1% (VFEND; Pfizer, New York) eye-drops were added along with oral voriconazole 200 mg twice daily. The patient was continued on natamycin sulfate (5%) eye-drops every 2 h. If no response to this combined therapy was observed after two more weeks, the patients received intrastromal injection of voriconazole (50 μg/0.1 ml) around the fungal infiltrate. Topical (1%) and intrastromal voriconazole (50 μg in 0.1 ml) were prepared to the desired concentration respectively using Ringer lactate.8 Injection voriconazole (VFEND) is available as 200 mg of white lyophilised powder in a glass phial. This was prepared in our hospital pharmacy in a class X atmosphere (highly sterile zone). The powder was reconstituted with 19 ml of lactated Ringer solution (LR) to obtain 20 ml of clear concentrate containing 10 mg/ml of voriconazole. A 1 ml aliquot of this solution was further diluted with 20 ml of LR to a concentration of 0.5 mg/ml (50 μg/0.1 ml) for injection. The reconstituted intrastromal voriconazole in the dose of 50 μg/0.1 ml was prepared fresh each time. However, the topical 1% voriconazole solution was stored under aseptic conditions at a temperature of 2–8°C under refrigeration for 1 week.10
Postintrastromal injection, the patients received topical voriconazole (1%) every 2 h along with oral voriconazole 200 mg twice daily. Topical therapy was continued until 2 weeks after the resolution of the infection. All patients received oral voriconazole 200 mg twice daily for a period of 4 weeks. A liver-function test and renal function test were carried out in all patients at baseline, and 2 weeks and 4 weeks of oral voriconazole therapy. In case of worsening or no response to the previous injection, intrastromal injection was repeated at 72 h.
Technique of injection
All injections were given under peribulbar anaesthesia under aseptic conditions, using an operating microscope. Fifty micrograms of voriconazole in 0.1 ml of Ringer lactate was loaded in a tuberculin syringe, and with the bevel down, the 27-gauge needle was inserted obliquely from the uninvolved, clear area to reach just flush to the abscess at the mid-stromal level (intended level for depositing the drug) in each case. Voriconazole (0.05 ml) was injected in five divided doses around the ulcer to form a drug deposit around the circumference of the lesion. This was done in such a manner that a centripetally directed progressive wave of fluid appeared to encompass the abscess along each meridian (figure 1). The degree of hydration of the cornea was used as a guide to assess the area covered.
A 360° wave of hydration due to intrastromal voriconazole, which forms a barrage around the ulcer.
Results
The mean age of the patients was 47.58±15.13 years. There were eight males and four females. The risk factors identified in these cases were trauma with vegetable matter (n=7) and use of topical corticosteroid drops (n=2). The mean time to presentation at our centre was 37.58±10.54 days from the onset of symptoms. The size of the ulcer varied from 3.0 to 6.8 mm, and the size of infiltrate varied from 4.0 to 8.2 mm (table 1). KOH wet-mount preparation revealed the presence of hyphae in 10 out of 12 patients (83.33%). The organisms isolated were Aspergillus species in eight eyes, Fusarium species in three eyes and Curvularia in one patient.
Presentation and final outcome of cases with recalcitrant fungal keratitis that received intrastromal voriconazole
Of the 12 patients enrolled in the study, intrastromal injections of voriconazole helped to resolve the infection in 10 cases without any complications. Seven patients received intrastromal voriconazole twice, while three patients received the injection three times. All patients complained of slight pain immediately after the injection. The mean healing time was 39.75±7.62 days. In two cases, treatment with intrastromal injections failed, and these cases developed corneal perforation, requiring emergency penetrating keratoplasty. These two perforated eyes had received three injections each. Of these, one patient was diabetic with adequate control of blood-glucose levels on insulin therapy. The organism identified in this case was Aspergillus niger, and the size of the ulcer was 5.4×6.8 mm at presentation. In the second case, the organism identified was Fusarium, and the size of the ulcer was 4.0×6.2 mm at presentation. The best-corrected visual acuity (BCVA) was less than 20/1200 in all patients at the time of presentation, which improved to better than 20/400 in 10 eyes and better than 20/200 in seven out of 10 eyes. Two patients who underwent therapeutic penetrating keratoplasty gained a BCVA of 20/40 each at the last follow-up. One patient had intrastromal haemorrhage, which resolved after 2 weeks without any intervention. No recurrence of keratitis was noted after the resolution of infection or postkeratoplasty. The mean duration of follow-up was 24.75±2.14 weeks.
Discussion
Fungal keratitis can present as superficial keratitis, corneal abscess and endothelial plaque, and may be associated with hypopyon. The commonly available antifungal agents are amphotericin B, natamycin, fluconazole, ketoconazole, 5-flucytosine, itraconazole and voriconazole. The fungistatic activity of amphotericin B is limited against filamentous fungi, and its systemic use is associated with various side effects.11 Natamycin has poor corneal penetration and precipitates on the corneal surface.12 In vitro susceptibility data show that voriconazole has the best efficacy against pathogenic fungi compared with other agents.13–15
It is evident from previous studies that oral and topical antifungal agents have poor ocular penetration, thereby achieving suboptimal drug levels at the site of infection.3–5 12 Hence, targeted drug delivery is required to achieve adequate drug levels at the site of infection.16–19 In order to achieve adequate intracorneal concentration of antifungals, intrastromal injections of antifungals have been tried.7–9 In our cases, the drug was injected around the abscess to form a drug deposit around the circumference of the lesion. This was done in such a manner that a centripetally directed progressive wave of fluid appeared to encompass the abscess along each meridian. Circumferential injection ensured the formation of a barrage of intrastromal voriconazole around the entire abscess. In all cases reported in the literature so far, intrastromal injections of antifungal agents were used as a last resort in order to treat cases having recalcitrant fungal infection not responding to conventional therapy. In our series, all ulcers had deep stromal infiltrates and were unresponsive to 4 weeks of topical oral antifungal treatment. In 10 eyes, the lesions were unresponsive to first intrastromal injection and required two or more injections for complete resolution. The injections were repeated at 72 h intervals. In three patients, injections were given three times. Repeat injections have been given once in one case report previously, with good results. In our case series also, there were no untoward effects of repeat injections.9 While ulcers resolved completely in 10 eyes, two patients developed corneal perforations, indicating treatment failure, and required therapeutic penetrating keratoplasty.
In the available literature, intrastromal and intravitreal injections of amphotericin B have been used in a patient who had a graft infection with endophthalmitis.7 Prakash et al reported successful use of intrastromal voriconazole in three patients of fungal keratitis.8 Tu reported success with intrastromal voriconazole in cases of Alternaria infection.9 Jain et al reported a good outcome in a case of fungal infection of the phacoemulsification site tunnel with intrastromal voriconazole.20 Our study has the largest series of patients with fungal keratitis treated with intrastromal voriconazole injection with a success rate of 83.33% (10 of 12 eyes) at the end of 24.75±2.14 weeks' follow-up.
The exact dose of the drug and frequency of injections to be administered are still to be determined. None of our patients developed any toxic effects with the drug after the injection. Further studies and randomised controlled trials are recommended before this choice of treatment assumes a standard approach. Nonetheless, we can conclude that judicious and timely use of intrastromal voriconazole injection as an adjunctive therapy may be undertaken in selected patients who are unresponsive to other forms of antifungal therapy. The major advantage of this treatment modality is that it delivers the drug at the site of infection, achieving a high intracorneal concentration, which may not be possible with topical and systemic antifungal therapy.
References
Footnotes
Competing interests None.
Patient consent Obtained.
Ethics approval Ethics approval was provided by the R P Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi.
Provenance and peer review Not commissioned; externally peer reviewed.
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