Ocular toxocariasis. A review

This review is an update on the subject of ocular toxocariasis. An introductory section is designed to familiarize the clinician with the epidemiology, characteristics of the organism, the life cycle in dogs and the systemic human disease known as visceral larval migrans (VLM). The more comprehensive second section considers the historical aspects of the ocular involvement, the clinical variations of ocular toxocariasis, pathology, differential diagnosis, diagnostic approaches, and treatment. Emphasis is placed upon new diagnostic techniques such as the enzyme-linked immunosorbant assay (ELISA) and cytologic diagnosis of intraocular aspirates. Newer therapeutic techniques such as vitrectomy are also considered. The review includes 200 references on systemic and ocular toxocariasis.     

Ocular toxocariasis in Korea

Purpose  

To analyze the characteristics and clinical manifestations of clinically diagnosed and serologically confirmed ocular toxocariasis in patients.     

Ocular toxocariasis. A case report

CASE REPORT: We present the case of a seven-year-old male with ocular toxocariasis. The fundus of the eye showed a vitritis, as a result of which the retina could not be seen. Following treatment with systemic corticosteroids the condition evolved favorably. However, due to a papillary and peripheral granuloma that raised the macula, a vitrectomy was performed which stabilized the process. DISCUSSION: Ocular toxocariasis is not common in developed countries. The diagnosis is based on funduscopic aspects, serology and IgG positivity of the vitreous. In relation to treatment, as the use of anthelminthics therapy is controversial, the use of corticosteroids and vitrectomy is recommended.     

Ocular toxocariasis. Diagnostic and therapeutic attainments

Toxocara canis is nematode parasite of dogs. Children are particularly subject to infestation, however the larva remains quiescent at stage II. Toxocara can localize in the eye and induce a variety of clinical manifestations. A case of ocular toxocara is presented in which there was granulomatous endophthalmitis. Immunologic testing was negative in the serum but positive in the vitreous, where numerous eosinophils and plasma cells where found. Vitreous and aqueous IgE levels were elevated. Corticosteroid therapy was ineffective in quieting the inflammation, but vitrectomy was beneficial. Biological testing demonstrated the advantages of using specific antigens with ELISA techniques. Negative test results in the serum do not obviate the need to perform assays of the aqueous and/or vitreous. The demonstration of an eosinophilic inflammatory response and elevated IgE levels support the diagnosis of ocular parasite infection. In the absence of specific anti-parasite therapy corticosteroid treatment appears to yield inconsistent results. Vitrectomy seems to be beneficial in these circumstances. The new diagnostic technique should improve the accuracy of ocular toxocara diagnoses.     

Ocular toxocariasis. Value of local immunodiagnosis

Toxocara canis is a nematode that may be involved in human ocular toxocariasis. Specific immunotesting is of importance but may be negative as toxocara antigens may localize exclusively in vitreous humor. We report here the case of one patient with optic disc toxocariasis granuloma negative for toxocara canis immunodiagnostic on serum. Clinical diagnosis was confirmed by toxocara canis specific enzyme-linked immunosorbent assay (ELISA) on aqueous humor showing elevated titers of antibodies. Systemic steroids associated to specific treatment of toxocariasis were initiated. Follow-up displayed regression of uveitis but development of vitreous bands leading to posterior retinal detachment. Toxocara posterior granuloma is of poor visual prognosis. Moreover, diagnosis may be of late setting, as clinical features are often unrecognized and specific immunodiagnostic on serum negative. Specific immunotesting on aqueous humor is of particular importance to rule out severe clinical differential diagnosis such as retinoblastoma in children. Ultrasound biomicroscopy (UBM) seems to be specific and sensitive in patients with a presumed diagnosis of peripheral toxocariasis. Granuloma surgery appears to yield good clinical results and allows histological confirmation of the diagnosis.     

Ocular toxocariasis in children and youth

The number of infections with larvae of the Toxocara canis worm has been continuously increasing in the Polish population, and the diagnosis and treatment of this disease is difficult. The authors describe 81 cases of eye infection in children and youth at the age of 3 to 18 years. The lesions in 94 eyes were observed for 0.5 to 11 years. In all patients the diagnosis was confirmed by ELISA test. In the clinical picture various forms of uveitis and granuloma of the eye fundus were found. The treatment consisted in general and topical application of antihelmintics, antibiotics and corticosteroids. In 23 eyes photocoagulation, in 11 cryopexy, and in 3 vitrectomy was performed. Clinical improvement was observed in 50 eyes, stabilization of the lesions in 41 eyes, and deterioration in the remaining 3 eyes. The authors conclude that the best results are obtained through conservative treatment combined with photocoagulation and cryopexy.     

Ocular toxoplasmosis and toxocariasis in childhood

Toxoplasmosis and toxocariasis are parasitic infections that are transmitted by cats and dogs, respectively, to humans, and which may induce posterior uveitis already in childhood. Toxoplasmosis presents as a congenitally or postnatally contracted infection whereas toxocariasis is always an acquired disease. The typical ocular sign of toxoplasmosis is retinochoroiditis, occurring as an active lesion, in most instances, associated with an inactive pigmented scar. In contrast, toxocariasis leads to a choroidal granuloma secondarily involving the retina or an endophthalmitis-like picture. Although toxoplasmosis represents the most common cause of posterior uveitis, there are uncertainties regarding the timing and specificity of the diagnosis, namely in atypical cases and those at risk of permanent severe loss of function. Antiparasitic treatment should be tailored to the severity of the inflammation and the risk of visual function loss. Concomitant steroids may be used to control the sequelae of unspecific inflammation, but should be used with caution and must be combined with an antimicrobial regimen. Because it is a rare disorder, one may not be familiar with the clinical presentation and suggested therapy for ocular toxocariasis. With this survey we, therefore, wish to provide a current, practice-oriented overview on the infection, ocular manifestations, diagnosis and treatment of ocular toxoplasmosis and toxocariasis in childhood.     

Ocular toxocariasis: A presumed case of peripheral granuloma

We report a case of peripheral Toxocara granuloma in a young boy of 17. Of the 3 forms of ocular toxocariasis, macular granuloma, endophthalmitis and peripheral granuloma, the latter is the least common and is characterized by the retention of relatively good vision.A differential diagnosis was performed between an intraocular foreign body encapsulated in fibroglial tissue, toxoplasmic retinochoroiditis, retinoblastoma, intermediate uveitis and toxocariasis.Fluorescein angiography showed not only some neovascularizations at the level of the peripheral granuloma but also manifestations of inflammatory reactions at the level of the posterior pole, i.e. diffuse leakages from retinal capillaries and parietal staining of some venous segments.Among the various laboratory tests, the most significant are eosinophilia, IgE concentration and detection of specific antibodies in serum as well as in aqueous humour.     

Ocular toxocariasis in 16-year old boy: a case report

The authors present a case of 16-year old boy with unilateral neurochorioretinitis induced by toxocariasis. Quick diagnosis and effective treatment allowed to obtain clinical improvement.     

Ocular biometry and refraction in Mongolian adults

OBJECTIVE: To describe the variation in ocular biometry and its association with refraction in adult Mongolians. METHODS: The study included 1800 subjects, aged 40 years or more, who were selected in two Mongolian provinces-H?vsg?l and Omn?gobi-to participate in this population survey. Axial length (AL) and its components, as well as noncycloplegic autorefraction and corneal power (CP), were measured. RESULTS: Of those selected, 1617 subjects (90.0%) were examined. Mean +/- SD of AL was 23.13 +/- 1.15 mm. There was a very small but significant increase in mean AL with age (0.05 mm per decade, P = 0.03). Autorefraction was performed on 620 of 675 subjects of those examined in Omn?gobi. The age and gender standardized prevalences of myopia (< -0.5 D), emmetropia, hyperopia (> +0.5 D), astigmatism (< -0.5 D of cylinder) and anisometropia (>1.0 D difference between eyes) were 17.2%, 49.9%, 32.9%, 40.9%, and 10.7%, respectively. Prevalence of myopia showed no clear trend with increasing age, whereas hyperopia, astigmatism, and anisometropia all increased monotonically. Multiple regression models revealed that AL (P < 0.001) and VCD (P < 0.001) were the strongest determinants of refractive error. CONCLUSIONS: In this cross-sectional study of adult Mongolians, a much lower prevalence of myopia was found than in other East Asian populations studied to date. The mean AL differed little between age groups, in marked contrast to data on Chinese people.     

Ultrasound biomicroscopy in peripheral retinovitreal toxocariasis.

PURPOSE: To report ultrasound biomicroscopic features in peripheral retinovitreal Toxocara uveitis. METHODS: Three patients with unilateral vitreitis suspected to be caused by peripheral toxocariasis were referred for ultrasound biomicroscopic examination of the peripheral retina, pars plana, and adjacent vitreous. RESULTS: In two of the three patients, characteristic pseudocystic transformation of the peripheral vitreous was seen. In both patients, Toxocara serology was positive and eosinophilia was present. In the third patient, no pseudocystic transformation of the peripheral vitreous was seen; however, there was the dense thickening adjacent to the pars plana usually seen by ultrasound biomicroscopy in pars planitis and corresponding to clinically visible snowbanks. The third patient had a negative Toxocara serology and later developed bilateral intermediate uveitis of the pars planitis type. In none of 48 patients with diverse inflammatory conditions of the retroiridal space that were examined by ultrasound biomicroscopy were the characteristic Toxocara-associated pseudocystic images seen. CONCLUSIONS: Pseudocystic transformation of the peripheral vitreous appears to be a rather specific and sensitive ultrasound biomicroscopic sign in patients with presumed peripheral toxocariasis that will likely aid diagnosis in difficult cases.     

Ocular problems of young adults in rural Nigeria

Objectives: To determine the common eye diseases as well as the prevalence and causes of blindness and visual impairment in young adult residents of rural areas of Anambra State, Nigeria. Materials and methods: Three rural villages in Anambra State, Nigeria were selected by simple random sampling. A structured questionnaire on demographic characteristics, symptoms and attitude to eye diseases was administered to residents aged 18–49 years. Ocular examination included visual acuity estimation, colour vision test, tonometry, refraction and ophthalmoscopy. Skin-snip was examined for microfilaria. Results: The common ocular problems in the 510 young adults examined were presbyopia (33.3%), refractive errors (41.1%), allergic conjunctivitis (8.2%), pterygium (8.2%), pingueculum (5.9%) and colour vision defect (2.4%). Bilateral blindness occurredin 1.2%, uniocular blindness in 0.8% and 1.7% had visual impairment in their better eyes. Glaucoma and sequelae of congenital cataract caused bilateral blindness while visual impairment was due to refractive errors, cataract, corneal opacities and uveitis. Trauma predisposed to uniocular blindness and visual impairment. Conclusions: Eyeglasses alone would alleviate visual impairment and ensure good near vision in more than 47% of the subjects. The prevalence of blindness could be reduced through early detection of glaucoma, congenital cataract and ocular trauma. This revised version was published online in July 2006 with corrections to the Cover Date.