Atypical presentation of acanthamoeba keratitis resembling central toxic keratopathy

Abstract

Purpose To describe an atypical case of acanthamoeba keratitis with positive in vivo confocal microscopy in a non-contact lens user who presented with signs and symptoms suggestive of central toxic keratopathy. Observations The patient presented with bilateral, though sequential, decreased visual acuity with mild pain. Examination showed stromal haze with corneal flattening and thinning without epithelial defects. Optical coherence tonometry of the right eye revealed an inverse dome-shaped appearance of the opacity and in-vivo confocal imaging showed double-walled cysts consistent with acanthamoeba. Corneal haze, stromal loss, resolved and visual acuity improved over time. Conclusion and importance Acanthamoeba is a rare cause of infectious keratitis that is most often associated with contact lens wear in developed countries. Typically, it presents with a unilateral decrease in visual acuity, photophobia, watering, and pain that is out of proportion to slit lamp examination findings. However, many atypical presentations have been reported in the literature. Consequently, it may be misdiagnosed, especially early in the course of the disease. This delay in diagnosis can lead to progressive ulceration and visual impairment. In addition, cyst formation can make eradication with anti-amoebic treatment especially difficult. Central toxic keratopathy is a non-inflammatory clinical syndrome of unknown etiology that is most often associated with excimer laser ablation, though other associated causes have been reported. It is characterized by a central or paracentral opacity with corneal stromal loss and resultant hyperopic shift. The opacification and stromal loss mostly resolve over the course of months with an improvement in visual acuity. This report may help physicians broaden their differential and correctly diagnose atypical presentations of amoebic infection.

Acute central corneal haze and thinning with atypical keratitis presentation

“…Unlike most patients with AK, this patient did not wear contact lenses, and the patient also has a brother who exhibited similar symptoms on 3 separate occasions. 5 Furthermore, there is little evidence that AK itself may have genetic or familial links. Up to 85% of infections occur in contact-lens wearers, but AK is also seen in those with ocular trauma, exposure to contaminated soil or water, and in healthy individuals in the absence of any of these risk factors.…”

“…Given the relative rarity of both AK and CTK, it is remarkable that both siblings share such similar presentations over the years, with the brother's case previously published in the literature. 4 A genetic predisposition for developing CTK must be considered. In 2022, I published a case report describing an isolated case of laser in situ keratomileusis (LASIK)-induced CTK in a pair of siblings from different households who underwent surgery the same day without any other affected cases seen.…”

“…1,2 There are also reports of atypical presentation of AK resembling central toxic keratopathy. 3 My diagnosis would be AK, and for diagnostic purposes, I would also perform confocal microscopy and cultures, as were performed by the treating physicians. There appears to be an inflammatory response to this infection, and it is fascinating as published previously that there is a familial predisposition.…”