Ocular mycosis: causes, symptoms, diagnosis, and treatment

Ocular mycosis is a fungal infection of various ocular tissues caused by superficial and deep fungi or conditioned pathogenic fungi. The most common is fungal corneal ulcer, followed by mycotic blepharitis, endophthalmitis, dacryocystitis, and orbital diseases. Mycotic endophthalmitis may have serious consequences, such as blindness or death from sepsis.


Causes

The main pathogens are Fusarium, Cephalosporium, and Aspergillus. Aspergillus includes Aspergillus fumigatus, Aspergillus flavus, Aspergillus versicolor, Aspergillus terreus, Aspergillus candidus, Aspergillus tamarii, Aspergillus japonicus, Aspergillus nidulans, and Aspergillus proliferans. Fusarium includes Fusarium solani, Fusarium venfricosum, Fusarium moniliforme, Fusarium equiseti, and Fusarium poae. Other pathogens of this disease are Cryptococcus, Candida, Sporotrichum, Dermatophytes, Penicillium, Paecilomyces variotii, Curvularia lunata, Alternaria alternata, Exophiala jeanselmei, Cylindrocarpon, Colletotrichum dematium, and Actinomycetes.

Ocular mycosis can be divided into exogenous infection and endogenous infection according to routes of infection.

Exogenous infections mostly occur in healthy individuals with intact immune functions, and the pathogens mainly enter ocular tissues through ocular trauma, dissemination of extraocular lesions, or surgical infections. Corneal ulcers caused by ocular trauma are more common. Mycotic endophthalmitis can be caused by surgical infections after penetrating keratoplasty, glaucoma filtration, cataract extraction, intraocular lens implantation, and scleral buckling.

Endogenous infections mostly occur in patients with systemic diseases and low body resistance, resulting from immunosuppressive therapy or dysbacteriosis and immune deficiency caused by the abuse of antibiotics. The pathogens are disseminated into the eye from the extraocular lesion in the blood circulation. Due to the presence of fungi in the conjunctival sac of healthy persons, long-term eye drops containing glucocorticoids and other drugs to suppress the immune response can also lead to the replication of fungi, thus causing the disease.


Signs and Symptoms

Mycotic blepharitis

The clinical manifestations vary depending upon the pathogens. For example, mycotic blepharitis caused by sporothrix is mainly manifested by nodules, abscesses, or granulomas; mycotic blepharitis caused by dermatophytes is characterized by central healing, and active edges composed of round or annular macules; and mycotic blepharitis caused by Aspergillus is manifested by small pustules, small nodules, and superficial ulcers. Subjective pruritus or mild burning pain are present.

Fungal corneal ulcer

Fungal corneal ulcer caused by trauma usually occurs 1 - 4 days after trauma. The average incubation period is 2 - 3 days. The symptoms are ocular redness, pain, and blurred vision. Although there are obvious opacity, congestion, corneal ulcers, and even empyesis, patients can open naturally their eyes due to absent blepharospasm, which is in sharp contrast to bacterial corneal ulcers.

The shape and color of the ulcer in this disease can be different depending on the different strains, but their common features are that the center of the ulcer is coated by sharply demarcated, grayish white or yellowish white hyphae, with coarse surface, slightly raised, with dense infiltration, with mild edema. The edges of the focal hyphae are coarse and unclear, and are surrounded by an annular inflammatory infiltration. Some lesions have radial or punctate satellite lesions. 1/2 of patients have empyesis, and the pus is mostly grayish white or light yellow. Corneal perforation can be seen in about 12% of patients. If there are concurrent bacterial and fungal infections, the disease develops rapidly. Sometimes, seclusion of pupil can cause fungal malignant glaucoma.

Figure 1 fungal corneal ulcer

Mycotic endophthalmitis

This illness is clinically characterized by slow onset, mild symptoms, and slow progression. The incubation period is several weeks to months, generally longer than that of bacterial endophthalmitis. The average incubation period is about 7 weeks in patients with postoperative infections and about 3 weeks in patients with trauma. The inflammations are often localized to the anterior chamber, pupil, or vitreous body, and are scattered or solitary, grayish white, punctate, small, round opacity. Some patients have diffuse inflammation, accompanied by acute redness, swelling, and pain. In few patients, extensive exudation in anterior chamber, increased intraocular pressure, or seclusion of pupil can cause fungal malignant glaucoma.

Figure 2 mycotic endophthalmitis


Diagnosis

On the basis of a history of trauma or surgery, clinical findings, positive fungal microscopy, and serological examinations, the disease can be diagnosed.


Treatment

Systemic treatment is generally used in patients with large and deep ulcers or perforations, and itraconazole is preferred. If the infection is caused by Cryptococcus neoformans or Candida, intravenous fluconazole is appropriate. Conditional pathogenic infections can be treated with miconazole diluted with 5% dextrose solution, and flucytosine can be administered as well.

Topical antifungal eye drops or oculentum, such as 0.1% aureofucinum eye drops, 1% aureomycin oculentum, 2 mg/mL amphotericin B eye drops, 1% silver sulfadiazine oculentum, 15% - 30% sulfacetamide sodium eye drops, 50,000 U/mL mycostatin eye drops, and 0.1% nipagin eye drops, can be administered once every half an hour.

Mydriatics can be used until the ulcer heals and the anterior chamber reaction completely subsides.

Debridement should be considered if necessary.