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Bowman’s layer encystment in cases of persistent Acanthamoeba keratitis

Authors Yokogawa H, Kobayashi A, Yamazaki N, Ishibashi, Oikawa, Tokoro, Sugiyama K

Received 6 June 2012

Accepted for publication 28 June 2012

Published 2 August 2012 Volume 2012:6 Pages 1245—1251

DOI https://doi.org/10.2147/OPTH.S34695

Checked for plagiarism Yes

Review by Single-blind

Peer reviewer comments 5

Hideaki Yokogawa,1 Akira Kobayashi,1 Natsuko Yamazaki,1 Yasuhisa Ishibashi,2 Yosaburo Oikawa,3 Masaharu Tokoro,4 Kazuhisa Sugiyama1

1Department of Ophthalmology, Kanazawa University Graduate School of Medical Science, Kanazawa, 2Department of Ophthalmology, East Washinomiya Hospital, Kuki, 3Department of Medical Zoology, Kanazawa Medical University, Kahoku, 4Department of Parasitology, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan

Background: The purpose of this study was to report Acanthamoeba encystment in Bowman’s layer in Japanese cases of persistent Acanthamoeba keratitis (AK).
Methods: Laser confocal microscopic images of the cornea were obtained in vivo from 18 consecutive eyes from 17 confirmed AK patients. Retrospectively, 14 cases treated over 4 months were categorized as a nonpersistent group and three cases that required prolonged therapy for more than 6 months were categorized as a persistent group. Clinical outcomes based on final best-corrected visual acuity were retrospectively analyzed, and selected confocal images were evaluated qualitatively for abnormal findings.
Results: The final best-corrected visual acuity was significantly lower (P < 0.01) for patients in the persistent group compared with that in the nonpersistent group. At the initial visit, in vivo confocal microscopy demonstrated Acanthamoeba cysts exclusively in the epithelial layer in both the nonpersistent group (80%) and the persistent group (100%). At a subsequent follow-up visit, numerous Acanthamoeba cysts were observed in the epithelial cell layer and in Bowman’s layer in all patients with persistent AK, but Acanthamoeba cysts were undetectable in all cases with nonpersistent AK tested.
Conclusion: Invasion of cysts into Bowman’s layer was characteristically observed in patients with persistence of AK. This finding suggests that invasion of Acanthamoeba cysts into Bowman’s layer may be a useful predictor for a persistent clinical course.

Keywords: Acanthamoeba keratitis, Bowman’s layer, encystment

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