Clinical features and course of ocular toxocariasis in adults

Abstract

Purpose: To investigate the clinical features, clinical course of granuloma, serologic findings, treatment outcome, and probable infection sources in adult patients with ocular toxocariasis (OT).

Methods: In this retrospective cohort study, we examined 101 adult patients diagnosed clinically and serologically with OT. Serial fundus photographs and spectral domain optical coherence tomography images of all the patients were reviewed. A clinic-based case-control study on pet ownership, occupation, and raw meat ingestion history was performed to investigate the possible infection sources.

Results: Among the patients diagnosed clinically and serologically with OT, 69.6% showed elevated immunoglobulin E (IgE) levels. Granuloma in OT involved all retinal layers and several vitreoretinal comorbidities were noted depending on the location of granuloma: posterior pole granuloma was associated with epiretinal membrane and retinal nerve fiber layer defects, whereas peripheral granuloma was associated with vitreous opacity. Intraocular migration of granuloma was observed in 15 of 93 patients (16.1%). Treatment with albendazole (400 mg twice a day for 2 weeks) and corticosteroids (oral prednisolone; 0.5-1 mg/kg/day) resulted in comparable outcomes to patients on corticosteroid monotherapy; however, the 6-month recurrence rate in patients treated with combined therapy (17.4%) was significantly lower than that in patients treated with corticosteroid monotherapy (54.5%, P=0.045). Ingestion of raw cow liver (80.8%) or meat (71.2%) was significantly more common in OT patients than healthy controls.

Conclusions: Our study discusses the diagnosis, treatment, and prevention strategies for OT. Evaluation of total IgE, in addition to anti-toxocara antibody, can assist in the serologic diagnosis of OT. Combined albendazole and corticosteroid therapy may reduce intraocular inflammation and recurrence. Migrating feature of granuloma is clinically important and may further suggest the diagnosis of OT. Clinicians need to carefully examine comorbid conditions for OT. OT may be associated with ingestion of uncooked meat, especially raw cow liver, in adult patients.

Figure 1. Funduscopic findings of ocular toxocariasis: Small amorphous posterior pole granulomas (A, B) with retinal nerve fiber layer defects (arrows), peripheral granulomas with round vitreous debris (C, arrow) and a tractional retinal fold (D), and vitreous findings, including tractional retinal detachment (E), whitish dot-like vitreous opacities, and vitreous veil (F).

Figure 2. Spectral domain optical coherence tomography (SD-OCT) shows granulomas in the outer (A), inner (B), and all retinal layers (C) as reflective masses with posterior shadowing.

The masses remarkably distort the retina and may be accompanied by the epiretinal membrane (B, arrow) and photoreceptor disruption (within two arrowheads). Dotted lines denote the scanned area.

Figure 3. Spectral domain optical coherence tomography (SD-OCT) images showing progressive retinal damage by ocular toxocariasis granulomas.

(A) Before discontinuous migration, a normal macular structure is visible, but scattered hyper-reflective dots indicate vitritis. (B) After discontinuous migration from the peripheral retina to the macula, a macular granuloma is observed in the inner retinal layers. (C) One month later, the inner retinal layers show severe distortion, a thick epiretinal membrane is present, and the granuloma extends to the outer retinal layers. (D) Three months after vitrectomy and epiretinal membrane removal, structural damage has not completely resolved.

Figure 4. Clinical course of granuloma in ocular toxocariasis.

Fundus photographs taken at diagnosis (left column) and the last visit (right column) show several patterns. Complete resolution (A), partial resolution (B), partial resolution of retinal infiltrate with pigmented scar (C), and the remains of an inactive granuloma (D). Each photograph is labeled with the follow-up time in months (mo). Double arrow in B denotes retinal nerve fiber layer defect.

Figure 5. Continuous (A–D) and discontinuous (E–H) migration of Toxocara granuloma.

(A) The granuloma shape is horizontally long, and the larva lies at the same level as the macula at the time of diagnosis. (B) Gradual inferior granuloma migration is observed. (C) The granuloma has turned toward the inferonasal side. The dotted line denotes a reference line connecting the fovea and inferior optic disc margin. (D) Retinal nerve fiber layer defect (double arrow) remains along the granuloma migration path 41 months after diagnosis. (E) Peripapillary granuloma with macular hard exudate. (F) Four months later, a new granuloma appears along the superotemporal arcade and a tractional membrane extends from the granuloma to the superotemporal vascular arcade and to the inferotemporal retina. A tractional membrane is also noted around the macula. (G) One month later, 2 novel granulomas appear in the macula and inferotemporal retina. (H) Ten months later, the inferior granuloma disappears and the macular granuloma is decreased in size, but multiple retinal nerve fiber layer defects remain (arrows).