November 03, 2020
6 min read
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Man presents with red, painful eye after foreign body injury

The patient received treatment, but his symptoms continued to worsen 10 days after his injury.

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A 62-year-old man with no medical or ophthalmic history presented to the Lahey Clinic ophthalmology department with a red, painful right eye and decreased vision for 10 days after foreign body injury.

Christine Benador-Shen
Christine Benador-Shen
Malgorzata Dymerska Peterson
Malgorzata Dymerska Peterson

The injury occurred while performing construction work on a water-damaged ceiling and involved wood debris falling into the patient’s right eye. The eye was immediately irrigated with sterile saline. The patient was seen by an outside ophthalmologist 2 days after the injury and was prescribed topical loteprednol and topical ciprofloxacin; however, only loteprednol was administered by the patient. The patient’s eye irritation subsequently worsened, prompting him to return to his local ophthalmologist 8 days after the injury, at which time he was started on oral acyclovir and topical neomycin-polymyxin-dexamethasone ointment for presumed herpes simplex virus keratitis. Ten days post-injury, he was referred to our clinic with worsening symptoms.

Examination and initial management

Upon initial examination in our clinic, visual acuity was 20/400 in the right eye and 20/40 in the left eye. Examination of the right eye revealed hyperemic conjunctiva with 3+ diffuse conjunctival injection, a large mid-peripheral ring-shaped corneal epithelial defect with intact but loose central epithelium, mild diffuse stromal edema, no corneal thinning, anterior chamber with 2+ cell and limited view to the posterior pole due to corneal edema (Figure 1). Examination of the left eye was normal. B-scan ultrasonography of the right eye did not reveal any vitritis, posterior masses or retinal detachments.

Anterior segment photos taken at presentation
Figure 1. Anterior segment photos taken at presentation to our clinic, 10 days post-injury. Hyperemic conjunctiva with 3+ injection and a large peripheral ring-like corneal epithelial defect (left). Fluorescein staining under cobalt blue filter with intact but loose central corneal epithelium and mild diffuse stromal edema (right).

Source: Allison V. Coombs, DO, MS, and Naveen K Rao, MD

Bacterial, fungal and Acanthamoeba corneal cultures were obtained. A viral swab was also obtained for HSV polymerase chain reaction (PCR) testing. The patient was started empirically on topical gatifloxacin eye drops four times daily and cyclopentolate eye drops twice daily. Topical neomycin-polymyxin-dexamethasone ointment and systemic acyclovir were continued while cultures were pending. Bacterial cultures returned positive for Staphylococcus aureus and Propionibacterium acnes. Fungal and Acanthamoeba cultures were negative. HSV PCR was also negative.

Anterior segment photo demonstrating clinical deterioration
Figure 2. Anterior segment photo demonstrating clinical deterioration, including violaceous hue of the sclera, dilated scleral vessels, complete 9 mm by 9 mm central corneal epithelial defect, 360° dense peripheral ring-like corneal infiltrate and worsening corneal edema (a). Fluorescein staining under cobalt blue filter demonstrating large corneal epithelial defect (b).

Medical management was optimized to include topical gatifloxacin every 2 hours, and topical prednisolone acetate was added once the epithelial defect improved. Despite medical therapy, the patient worsened clinically and developed severe pain, violaceous hue of the sclera, dilated scleral vessels, complete 9 mm by 9 mm central epithelial defect, 360° dense peripheral ring-like corneal infiltrate, worsening corneal edema and, several days later, a hypopyon that filled 60% of the anterior chamber (Figures 2 and 3).

Hypopyon
Figure 3. Hypopyon and severe clinical worsening pre-hospitalization.

Imaging

Confocal microscopy of the right eye revealed active trophozoite disease, with many cysts within the corneal stroma, involving the periphery of the cornea and the sclera (Figure 4).

Confocal microscopy of the right eye
Figure 4. Confocal microscopy of the right eye revealing cysts (yellow arrow) throughout the corneal stroma, some in linear chain-like formation, and trophozoites (red arrow).

What is your diagnosis?

See answer below.

Red, painful eye

Sclerokeratitis can be attributable to infectious, rheumatologic and inflammatory etiologies. Our patient had infectious keratitis and subsequently developed scleritis despite appropriate therapies for bacterial, viral and inflammatory conditions. This clinical course suggested an infectious etiology spreading from the cornea to the sclera. Confocal microscopy revealed trophozoite and cystic structures within the sclera and cornea, consistent with Acanthamoeba sclerokeratitis with bacterial superinfection, despite negative Acanthamoeba culture.

Further management

Treatment of our patient’s Acanthamoeba sclerokeratitis and bacterial superinfection included topical chlorhexidine, topical polyhexamethylene biguanide, systemic and topical voriconazole, topical cefazolin and topical gatifloxacin. The patient was admitted to the hospital for intravenous treatment with pentamidine, systemic steroids and miltefosine. Upon admission, intravenous methylprednisolone was used to help control inflammation and pain and was later tapered to oral prednisone. Intravenous pentamidine was administered for a 14-day course. Oral miltefosine, granted orphan drug designation for Acanthamoeba, was initiated on hospital day 4 but was stopped earlier than the planned 28-day course on day 22 due to adverse side effects of transaminitis, diabetic ketoacidosis and hypotension.

Clinical improvement was evident on day 4 of treatment, with improved vision and improved pain. The patient was discharged on hospital day 10 with 20/20- near vision in the right eye, 30% hypopyon and overall improved examination pertinent for 1+ diffuse conjunctival injection with ciliary flush, 6 mm by 9 mm central corneal epithelial defect with persistent 360° ring infiltrate and diffuse keratic precipitates (Figure 5).

Improved clinical exam at time of hospital discharge
Figure 5. Improved clinical exam at time of hospital discharge following systemic therapy for Acanthamoeba sclerokeratitis.

The therapeutic plan included optimizing medical management and, when improved, performing a therapeutic penetrating keratoplasty with a large diameter graft to encompass the entire infiltrate, avoiding vessels to minimize risk for graft rejection and early graft failure.

after therapeutic PK
Figure 6. Patient’s eye after therapeutic PK.
residual cysts within the central cornea
Figure 7. Host cornea removed during PK, stained with periodic acid-Schiff, demonstrating residual cysts within the central cornea.

Three weeks after initiating therapy for Acanthamoeba, confocal microscopy was repeated and revealed clearing of the organisms in the sclera and corneal periphery. Therapeutic PK was successfully performed (Figure 6), and surgical pathology confirmed Acanthamoeba cysts throughout the removed central corneal tissue (Figure 7). More than 1 year later, the patient has not had recurrence of disease, as evidenced by confocal microscopy (Figure 8).

Follow-up confocal microscopy
Figure 8. Follow-up confocal microscopy revealing no evidence of Acanthamoeba throughout the corneal stroma.

Discussion

Acanthamoeba is a type of amoeba found living freely in aquatic environments. Risk factors for ocular Acanthamoeba infection include contact lens wear, corneal trauma, exposure to pond, lake and well water, and low levels of anti-acanthamoeba IgA levels in blood serum. Acanthamoeba typically infects the cornea only, but rarely also involves the sclera, resulting in Acanthamoeba sclerokeratitis. Our patient’s case was unique because the patient was not a contact lens wearer, had no known exposure to contaminated water sources and had aggressive disease involving the sclera. We speculated that the wood debris that contaminated the surface of the eye may have inoculated the cornea with dormant Acanthamoeba cysts, and subsequently the patient was superinfected with bacterial pathogens.

The Acanthamoeba life cycle includes two forms: mobile trophozoites and dormant cysts. Cysts are resistant to typical methods of eradication, including many topical therapies and radiation, and are able to resist desiccation for more than 21 years.

Acanthamoeba sclerokeratitis is a rare clinical entity that results from trophozoites and cysts migrating from the cornea to the well-vascularized sclera, creating a significant inflammatory reaction. Reported frequency of Acanthamoeba sclerokeratitis is estimated as 0.13 per 1 million. Clinical features of Acanthamoeba sclerokeratitis include typical features of Acanthamoeba keratitis: large central epithelial defect, ring-like peripheral corneal infiltrate, stromal edema and infiltrates, stellate lesions and radial keratoneuritis, in addition to signs and symptoms of scleritis: violaceous hue of the sclera and dilated scleral vessels that do not blanch with pharmacologic therapies. It may also include anterior uveitis, stromal thinning, corneal or scleral perforation/necrosis, and severe pain that may appear out of proportion to the exam findings.

The diagnosis of Acanthamoeba sclerokeratitis is similar to the diagnosis of Acanthamoeba keratitis and includes corneal culture, gram stain, biopsy and/or corneal scraping, PCR and confocal microscopy of both the cornea and sclera. Confocal microscopy in Acanthamoeba sclerokeratitis reveals linear hyperreflective round cysts and bright oval-shaped heterogeneous-appearing trophozoites within the corneal stroma and sclera.

Acanthamoeba sclerokeratitis has a poor prognosis, with most cases resulting in enucleation and/or numerous PKs with recurrence of disease. Our case demonstrates one successful approach using topical, systemic and surgical therapy.