Clinical and experimental findings in Acanthamoeba keratitis with Heidelberg Retina Tomograph III‐RCM

Abstract Purpose:  To observe Acanthamoeba cysts and trophozoites in the corneal tissue of patients and rabbits with Acanthamoeba keratitis (AK), using the Heidelberg Retina Tomograph III Rostock‐cornea‐module (HRTIII‐RCM). Methods:  Eight eyes of seven patients with clinical and laboratory diagnosis of AK, presenting to the Beijing Institute of Ophthalmology between July and December 2006, were included in this study. The laboratory diagnosis in all cases was established by a cytological analysis and culture of the corneal scraping. The scanning with HRTIII‐RCM was performed on all the patients. Acanthamoeba cysts and trophozoites in the corneas of three rabbits were observed with the HRTIII‐RCM after a suspension of trophozoites was injected into the corneal stromal layer of the rabbits. Results:  Acanthamoeba cysts or trophozoites were observed with the HRTIII‐RCM in the corneas of all the patients. The size and shape of Acanthamoeba in the tissue of the rabbit corneas was consistent with that in the patients’ eyes. The Acanthamoeba cyst presented a round high‐contrast particle, 15–20 μm in diameter, with a double wall. In contrast, the trophozoite presented an irregular high‐contrast particle, without an apparent wall, 25–40 μm in diameter and with a round conspicuous nucleus. Conclusions:  HRTIII‐RCM is a useful non‐invasive clinical technique to help to diagnose and monitor the response of AK to therapy.