The application of in vivo confocal scanning laser microscopy in the management of Acanthamoeba keratitis

Purpose: To evaluate the role of in vivo laser scanning confocal microscopy (Heidelberg Retina Tomograph II, Rostock Cornea Module, HRTII-RCM) in the management of Acanthamoeba keratitis (AK). Methods: Four eyes of four patients with AK seen at Keio University Hospital at the Department of Ophthalmology were studied in this single-center, prospective, interventional case series. All patients were routinely examined by slit-lamp microscopy including corneal fluorescein staining. Best corrected visual acuity (BCVA) was also measured before and after the treatment for AK. Both the scraped corneal epithelium and soft contact lens (SCL) storage solution in each patient's SCL case were cultured. Patient corneas were examined regularly using the HRTII-RCM before treatment and after commencement of medications including azoles, echinocandins, and chlorhexidine. Results: All patients had various degrees of conjunctival injection, corneal edema, stromal opacity with radial keratoneuritis with slit-lamp examination. Cultures for AK were positive in three out of four cases by corneal scraping. Contact lens storage solutions were also positive in three of four cases. HRTII-RCM examination could detect Acanthamoeba cysts or trophozoites in all eyes before corneal scraping. No organisms were detectable in any of the cases in any of the corneal layers four to six weeks after treatment. The BCVA improved with treatment in three of four eyes. Conclusions: HRTII-RCM could effectively demonstrate cysts and trophozoites and the nature of the inflammatory process in AK. In vivo laser scanning confocal microscopy employing HRTII-RCM could provide an end-point for treatment, saving the patient from additional invasive diagnostic procedures and unneeded exposure to long term topical or systemic medications.