Nematode infections of the eye: toxocariasis,onchocerciasis, diffuse unilateral subacute neuroretinitis,and cysticercosis

Nematode infections of the eye are common in different parts of the world, but some are usually encountered only in developing nations, such as onchocerciasis and cysticercosis. Ocular toxocariasis is a well-known cause of unilateral ocular disease affecting mainly children and young adults, and is usually caused by T canis. Prevention of ocular toxocariasis is based on such measures as appropriate health care for dogs and cats, including regular anthelmintic treatments, preventing contamination of the environment with feces, and promoting responsible pet ownership [1,49-51]. Onchocerciasis is caused by infection with the filarial parasite O volvulus, and occurs in endemic areas along rivers and streams. In hyperendemic areas almost every person is infected and about half of the population is eventually blinded by onchocerciasis. Because of this, elimination of host-vector contact is very important. DUSN is caused by a motile nematode and is found in the Southeastern and Midwestern United States and in many parts of the world. In Brazil, DUSN is becoming an important cause of posterior uveitis in children and young healthy adults. The destruction of the worm during the early stages of the disease can prevent progression of the visual loss. It is important to remain aware of this entity, not only in areas where it has been described, but also in regions not yet identified as being endemic [52]. Cysticercosis is caused by the encystment of the larvae of the tapeworm T solium, and usually results from ingesting eggs from food, water, or other material contaminated with human feces. Surgical removal of the cyst is usually indicated when possible.     

Diffuse unilateral subacute neuroretinitis.

The clinical syndrome of diffuse unilateral subacute neuroretinopathy (DUSN) has been characterised in its early and late stages. Different types of migrating worms in the subretinal and intraretinal space have been described as the cause of the clinical syndrome. We observed a patient with a long history of visual loss, vitritis, and a fundus of abnormal appearance where the worm was noted to migrate to different areas over the course of hours.     

Diffuse unilateral subacute neuroretinitis.

BACKGROUND: Diffuse unilateral subacute neuroretinitis (DUSN) is an inflammatory disorder of the retina thought to be caused by a motile worm. It initially presents with unilateral recurring crops of gray-white retinal lesions and mild to severe inflammation. Over a period of months, diffuse retinal pigment epithelium (RPE) changes, arteriolar attenuation, and optic atrophy will develop. In approximately 25% of cases, a worm is visualized during the eye examination. Laser treatment to kill the worm is the only reliable way to halt progression of this disease. METHODS: The following case report presents a 9-year-old girl with unilateral vision loss. RESULTS: Clinical observation and several blood tests to rule out systemic diseases resulted in a diagnosis of DUSN. Although a worm was not visualized, laser treatment of its suspected location resulted in recovery of some vision. CONCLUSIONS: DUSN is often diagnosed by clinical presentation alone, because a worm may not be visualized. An appropriate initial work-up and timely initiation of laser treatment are essential to preservation of vision.     

Hypopyon in a patient with presumptive diffuse unilateral subacute neuroretinitis

PURPOSE: To report a case of diffuse unilateral subacute neuroretinitis (DUSN) that developed an acute iridocyclitis with hypopyon. METHODS: Case report. We describe a 21-year-old male with clinical diagnosis of DUSN who developed a sudden and severe acute iridocyclitis with hypopyon after one year of follow-up that resolved after treatment with systemic corticosteroids. RESULTS: Anterior chamber paracentesis was performed and cultures were negative. Cytologic studies disclosed the presence of eosinophils. CONCLUSIONS: This unusual ocular finding may be related to the death of the nematode in the course of the disease.     

Diffuse unilateral subacute neuroretinitis

Background In patients with diffuse unilateral subacute neuroretinitis (DUSN), the presence and, therefore, clinical visualization of subretinal nematode makes the diagnosis obvious. However when located under the retinal pigment epithelium (RPE), diagnosis is presumptive and challenging. We report a case of presumed DUSN to illustrate this diagnostic dilemma and to highlight the clinical signs which suggest the diagnosis. Methods Case report of a patient with DUSN. Results In our patient the nematode was not located subretinally and this made the diagnosis difficult. However, the appearance of sub-RPE serpiginous tract in the infero-temporal retina, peripheral RPE hypopigmentation and good clinical response to anti-helminthics supported the diagnosis. Conclusions It is important to have a high index of suspicion when patients present with a combination of above findings. This will help in early control of ocular inflammation and salvaging vision.     

Diffuse unilateral subacute neuroretinitis

In December 1980, a 26-year-old black man came to the Washington Hospital Center Eye Clinic with a unilateral decrease in visual acuity, vitreous inflammation, optic disk pallor, and a degenerated retinal pigment epithelium. A motile subretinal worm was subsequently found. Unlike an earlier series of 18 patients with diffuse unilateral subacute neuroretinitis reported by other authors, this patient exhibited eosinophilia and a highly positive ELISA for Toxocara.     

Early-stage diffuse unilateral subacute neuroretinitis: improvement of vision after photocoagulation of the worm

PURPOSE: To evaluate the visual outcome after direct laser photocoagulation of the worm in patients with early-stage diffuse unilateral subacute neuroretinitis (DUSN). METHODS: We report on four patients with DUSN diagnosed in its early stage, in whom the worm was identified and destroyed by laser photocoagulation. RESULTS: In all the four cases, resolution of the inflammatory multifocal lesions was achieved within 1 month of treatment. After that period and during follow-up (mean 11.5 months), visual acuity improved in three eyes and remained unchanged in one eye. CONCLUSION: The diagnosis of DUSN in its early stage followed by prompt location and destruction of the worm by photocoagulation may improve vision of affected patients.