Acanthamoeba keratitis is a sight‐threatening contact lens‐related corneal infection disease, and often misdiagnosed as other common microbial infection. 1 Radial keratoneuritis, as an early and characteristic sign, is helpful to diagnose this confusing keratitis. 2
A 15‐year‐old girl presented to our emergency department with a history of gritty sensation, redness, photophobia, and blurred vision in her both eyes for 10 days. The best corrected visual acuity was 20/200 in the right eye and 20/100 in the left eye. She was an orthokeratology contact lens wearer who has rinsed her lens with tap water before wearing on a routine basis. Slit lamp biomicroscopy revealed conjunctival injection and corneal epithelial edema. Besides, multiple linear‐like infiltrates occurred in the center of both corneas and extended from the center to the limbus. Bilateral radial keratoneuritis, which consists of thickened corneal nerves with ragged perineural infiltrate, were appeared in the anterior and mid depths of the stroma. Besides, the whole surface of cornea was inflamed and showed sandy‐like pattern (Figure 1A, the right eye; Figure 1B, the left eye). According to the result of anterior segment optical coherence tomography (AS‐OCT) (Figure 1C, the right eye), horizontal scan at the 5‐o'clock position disclosed keratoneuritis as a highly reflective band running obliquely in the corneal stroma (Figure 1C, arrows). Corneal scraping was performed, and the samples stained with 10% potassium hydroxide (KOH) showed multiple double‐walled cyst structures consistent with Acanthamoeba spp. (Figure 1D, arrow). 3 Therefore, the diagnosis was bilateral acanthamoeba keratitis. The inpatient treatment included topical 0.02% polyhexamethylene biguanide combined with 0.02% chlorhexidine every 2 h for the first 2 weeks. Topical steroid (0.1% fluorometholone) twice daily and oral itraconazole (200 mg/day) were also administered. The frequency of topical instillation was then tapered according to clinical response and kept twice daily for the additional 3 weeks even after the healing of corneal infiltrates. 4 The infection was under control with resolved stromal edema and the infiltrates turned to faint subepithelial scar (Figure 1E, the right eye; Figure 1F, the left eye). Besides, the width of the bands in the corneal stroma decreased and the margin became clear by AS‐OCT (Figure 1G). The final best‐corrected visual acuity recovered to 20/20 in the right eye and 20/15 in the left eye. The infection did not recur during the 6‐month follow‐up period.
FIGURE 1.
(A) Slit‐lamp photograph of the right cornea. Apparent keratoneuritis was observed at the whole corneal area. (B) Slit‐lamp photograph of the left cornea. Multiple radial keratoneuritis was observed. (C) Anterior segment OCT image of the right cornea. Horizontal scan showed corneal edema (central corneal thickness: 762 nm) and putative keratoneuritis as highly reflective bands at different areas in the corneal stroma (arrows). The different widths and depths of the reflective bands may correspond to the patchy lesions around keratoneuritis. (D) Acanthamoeba cyst on scraping with 10% KOH staining (white arrow) (original magnification: ×400). (E) Slit‐lamp photograph of the right cornea. Corneal infiltrates absorbed completely after 58 days of therapy. (F) Slit‐lamp photograph of the left cornea after treatment. (G) Anterior‐segment OCT image of the right cornea. Resolved corneal edema (central corneal thickness: 585 nm) and the decreased widths and intensities of the reflective bands showing in the corneal stroma (arrows)
High‐resolution AS‐OCT is a useful tool for visualization of microstructural image of cornea. It could identify the highly reflective bands presented by the swollen corneal nerves. 5 Besides, the width and intensity of the bands that correlate with the degree of inflammatory reaction around the keratoneuritis were helpful for tracking the prognosis and treatment efficacy of the disease.
In conclusion, acanthamoeba keratitis is an infectious complication of contact lens‐wearing. The presence of radial keratoneuritis helps to diagnose this disease at an early stage and thus prompt treatment being able to be given to yield the best visual outcome.
CONFLICT OF INTEREST
The authors declare no conflicts of interest.
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