Argon Laser as Adjunctive Therapy for Refractory Alternaria Fungal Keratitis: A Case Report

Abstract

Introduction

Fungal keratitis is an ocular emergency that requires early and appropriate management. It can lead to significant visual loss. Standard treatment includes topical and systemic antifungals. In refractory cases, adjuvant therapies have been explored. The argon laser has shown higher cure rates than other traditional therapies.

Case Presentation

We describe the case of a 55-year-old farmer with a 20-day history of foreign body sensation. The condition was classified as a fungal corneal ulcer caused by Alternaria spp. Argon laser treatment was performed with a 500-um spot for 0.2 s at 900 mW power. This led to a reduction in the corneal epithelial defect and complete healing.

Conclusion

Argon laser treatment for this refractory fungal ulcer resulted in complete healing of the epithelial defect, with minimal corneal opacity.

Introduction

Fungal keratitis is an ophthalmic emergency. It leads to severe complications, such as corneal scarring, structural deformities, visual loss, and risk of blindness [1, 2]. Many patients require keratoplasty; about 11% ultimately undergo evisceration [1–4]. Agricultural workers are most affected. This has prompted proposals to list it as a neglected tropical disease in ophthalmology [2, 5]. Aspergillus spp. are the most common pathogens. Alternaria spp. are rare, causing 3.3–8.7% of cases, mostly in immunocompromised patients or those with prior surgery or trauma [6–8]. Treatment relies on topical and systemic antifungals. However, resistance based on culture and sensitivity may lead to poor responses [9]. In refractory cases, adjuvant therapies include keratoplasty, amniotic membrane transplantation, intraocular or intrastromal antifungals, and argon laser photocoagulation [10]. The argon laser induces thermal cellular damage via protein denaturation and coagulation, which may exert a fungicidal effect. Compared with other adjuvant options, such as intrastromal voriconazole, it has shown promising results in patients with ulcers refractory to initial treatment [10, 11]. This report outlines the use of argon laser as an adjunct therapy for refractory fungal keratitis, a corneal infection linked to significant vision loss, especially in developing countries.

Case Presentation

A 55-year-old male agricultural worker with no relevant medical history or prior ocular trauma presented with a 20-day history of foreign body sensation, photophobia, and decreased visual acuity in the right eye as shown in Table 1. On ophthalmologic examination, the patient’s best-corrected visual acuity measured 20/70. Slit-lamp biomicroscopy demonstrated ciliary injection and moderate conjunctival hyperemia. A single paracentral corneal epithelial defect was observed in the inferotemporal quadrant (from 3 to 6 o’clock), measuring approximately 6.5 × 5 mm with irregular, poorly demarcated edges. This lesion was accompanied by a stromal infiltrate involving roughly 25% of the corneal depth (Fig. 1). Corneal scrapings were obtained for bacterial and fungal cultures. Empirical treatment with fortified topical voriconazole 1% and moxifloxacin 0.5% was initiated. Preliminary culture revealed a dematiaceous fungus, prompting a switch to amphotericin B 0.15%. Final cultures identified Alternaria spp. as the causative organism, as shown in Figure 2.

Table 1.

Timeline of clinical course, therapeutic interventions, and patient outcomes

Time course	Event	Findings/intervention
Day 20	Initial consultation	Foreign body sensation, photophobia, and decreased visual acuity in the right eye (OD)
Day 20	Initial examination	VA 20/70. Slit-lamp biomicroscopy: ciliary injection, moderate conjunctival hyperemia, and inferotemporal paracentral corneal ulcer (6.5 × 5 mm) with approximately 25% stromal involvement
Day 20	Initial therapy	Topical voriconazole 1% + moxifloxacin 0.5%
Day 28	Poor clinical progression	Persistent stromal infiltrate with risk of visual axis involvement or perforation
Day 29	Adjuvant therapy	Three sessions of argon laser (500 µm spot, 0.2 s, 900 mW) applied to the center and margins of the ulcer
Day 45	Clinical resolution	Reduction of stromal infiltrate and progressive re-epithelialization
Day 45	Visual outcome	Resolution with residual corneal leukoma without complete involvement of the visual axis

Fig. 1.

Initial corneal ulcer with stromal infiltrate. Slit-lamp photograph at initial presentation showing an inferotemporal paracentral corneal ulcer with a dense stromal infiltrate and overlying epithelial defect. Associated findings include ciliary injection and moderate conjunctival hyperemia. The lesion involves approximately the anterior to mid-stromal layers.

Fig. 2.

Clinical response after argon laser therapy. Slit-lamp photograph following adjuvant argon laser therapy demonstrating reduction in stromal infiltrate and partial re-epithelialization. Conjunctival hyperemia persists but is less pronounced compared to baseline.

Given the slow clinical course after 8 days of topical treatment and the high risk of further visual axis compromise or even corneal perforation, adjuvant argon laser therapy (500 µm spot size, 0.2-s duration, 900 mW power) was chosen for three sessions. This was applied to the entire lesion, including its center and the entire margin of the ulcer. The primary objective was to contain the progression of the lesion and preserve the visual axis (Fig. 3). The intervention resulted in stabilization of the ulcer size, reduction of the stromal infiltrate, and progressive reepithelialization. Two weeks later, treatment was discontinued with favorable clinical resolution. A residual corneal leukoma persisted without total visual axis compromise, and the patient’s initial visual acuity was preserved.

Fig. 3.

Microscopic appearance of filamentous fungi. Microbiological examination (light microscopy) revealing filamentous fungal hyphae with septations, consistent with fungal keratitis.

This case report was prepared in accordance with the CARE guidelines, and the completed CARE checklist is provided as online supplementary material (for all online suppl. material, see https://doi.org/10.1159/000552130) [12].

Discussion

Fungal keratitis is an ophthalmic emergency. It has the potential to cause severe and permanent visual sequelae, even with timely treatment. Although immunosuppressed patients are at higher risk, this infection also occurs in immunocompetent individuals. It is particularly seen in those with repeated exposure to soil and plant material [13]. In the present case, a 55-year-old male agricultural worker developed fungal keratitis caused by Alternaria spp. This is a dematiaceous filamentous fungus found in plants. It is considered an uncommon but highly virulent opportunistic corneal pathogen [14].

Identifying the etiology of keratitis remains a clinical challenge. Microbiological studies are essential for distinguishing fungal from bacterial infections. While microscopy may rapidly suggest a fungal origin, culture allows definitive identification and treatment guidance. However, up to 25.6% of cases yield negative cultures [8, 15]. Antifungal therapy is mainly fungistatic and requires prolonged treatment of at least 12 weeks. Natamycin is the gold standard for filamentous fungal keratitis but is often unavailable or unaffordable in low- and middle-income settings. Amphotericin B is commonly used as an alternative, despite limited evidence and frequent treatment failure due to poor corneal penetration and resistance [3].

Given the lack of clinical response after 8 days of topical amphotericin B, adjuvant therapy was considered. Argon laser photocoagulation is increasingly reported for refractory fungal keratitis. It enhances antifungal penetration and directly destroys infected tissue [9–11]. In this case, laser treatment (500 μm, 0.2 s, 900 mW) progressively reduced the stromal infiltrate, controlled the resulting infection, and partially preserved the visual axis. This outcome supports the use of argon laser photocoagulation which is reported infrequently or as culture-proven alternatives as a useful adjunct to limit disease progression and reduce the need for therapeutic keratoplasty in resistant fungal keratitis [10, 11].

Conclusion

Keratitis caused by Alternaria spp. should be considered in immunocompetent individuals with environmental or agricultural exposure, particularly when the clinical course is poor despite antifungal therapy. Argon laser photocoagulation may be a useful adjunctive treatment to control localized infection and preserve vision in refractory cases, although its effectiveness remains to be validated and requires further local studies.

Statement of Ethics

This study protocol was reviewed and the need for approval was waived by Hospital Research Ethics Committee (CEISH) Hospital General del Sur de Quito – IESS. Written informed consent was obtained from the patient for publication of the details of their medical case and any accompanying images.

Conflict of Interest Statement

The authors have no conflicts of interest to declare.

Funding Sources

This study was not supported by any sponsor or funder.

Author Contributions

Conceptualization: G.C.C., D.O., and A.T.C.; methodology: E.Q.; writing original draft preparation: G.C.C. and M.P.; writing review and editing: E.Q. and J.R. revised the final manuscript. All authors have read and agreed to the published version of the manuscript.

Funding Statement

This study was not supported by any sponsor or funder.

Data Availability Statement

The data that support the findings of this study are not publicly available due to privacy reasons but are available from the corresponding author upon reasonable request.