Associated factors, diagnosis and management of Acanthamoeba keratitis in a referral Center in Southern China

Abstract

Background: To analyse the associated factors, diagnosis, clinical manifestations and therapeutic effects of Acanthamoeba keratitis at a tertiary ophthalmic centre in Southern China.

Methods: A retrospective clinical study was performed in fifteen patients who were admitted to Zhongshan Ophthalmic Centre (ZOC) from January 2004 to December 2014. The patients' pathogenesis-associated factors were analysed, and preoperative diagnoses were determined using corneal scraping cultures and/or confocal microscopy followed. All diagnoses were confirmed by postoperative pathological examinations. At follow-up, best-corrected visual acuity (BCVA), the recurrence rate and graft transparency were evaluated to assess therapeutic effects.

Results: The main pathogenic factors observed in the fifteen patients were a history of injury or a foreign body entering the eyes (12 cases). In all, Acanthamoeba keratitis was preoperatively diagnosed in 5 cases using corneal scraping cultures or confocal microscopy. Ocular symptoms included redness, photophobia, tearing, and blurred vision. Penetrating keratoplasty was performed in thirteen patients, and postoperative pathological examinations were performed to confirm these diagnoses. The logarithm of the minimum angle of resolution (logMAR) of visual acuity was significantly improved after keratoplasty (p < 0.01). No recurrence was observed, and approximately 90% of the corneal grafts were found to be transparent during the follow-up period.

Conclusions: Corneal trauma may be the main pathogenic factor that causes Acanthamoeba keratitis in southern China. Corneal scraping combined with confocal microscopy was helpful for achieving a correct diagnosis. Early keratoplasty combined with amoebicidal therapy is an effective treatment strategy in Acanthamoeba keratitis.

Keywords: Acanthamoeba keratitis; Associated factors; Diagnosis; Keratoplasty.

Fig. 1

Acanthamoeba keratitis is characterized by ring-like stromal infiltrates and corneal lesions (a). The cornea is relatively translucent in the centre of the ring infiltrates (b). Coinfection with fungi or bacteria contributes to variability and atypical symptoms. A cornea was infected with Acanthamoeba and Aspergillus (c). A cornea infected with Acanthamoeba, Mucor and E. coli (d)

Fig. 2

Pathological sections stained with HE revealed corneal oedema and amoebic cysts among the corneal collagenous fibres (blue arrow) (a-b). Numerous polymorphonuclear and mononucleated cells and nuclear debris had infiltrated the corneal stroma (c). Amoebic cysts and trophozoites were detected in the cornea (blue arrow) using PASM staining. Aspergillus hyphae (deep blue arrow) had fragmented in a coinfected case (d) (20 × 20)

Fig. 3

A moderately infected case (a) that was treated with conventional penetrating keratoplasty. The graft was transparent, and the depth of the anterior chamber was normal after six months (b). A seriously infected case (c) that was treated with large corneo-scleral penetrating keratoplasty. The donor cornea was clear after one month (d)

Fig. 4

Pre- and post-operative logMAR best corrected visual acuity of the patients. The data are shown as the mean ± SEM. *, p < 0.05; **, p < 0.01; and ***, p < 0.001