“Silent” Ocular Toxocariasis

Pars plana vitrectomy revealed Toxocara canis organism

BACKGROUND

The Toxocara organism may cause direct injury to the eye, but most commonly, host inflammatory reactions are responsible for the resulting compromise. The inflammatory response created by the ocular involvement may result in epiretinal membrane formation, tractional or combined tractional-rhegmatogenous retinal detachment. The treatment of choice is pars plana vitrectomy (PPV), which also has diagnostic significance.

METHODS

We report a pediatric case in which PPV recovered the Toxocara canis organism. For the total tractional retinal detachment diagnosed after the cataract surgery, PPV, preretinal and subretinal membrane peeling, 180 degrees retinotomy, silicone oil injection were performed. The fibrous membrane specimen obtained during PPV recovered the Toxocara canis organism.

RESULTS

The intense postoperative inflammatory reaction had to be managed surgically, also. Retinal reattachment was achieved with subsequent improvement of the visual acuity.

CONCLUSION

The importance of vitreous biopsy examination following PPV, in eyes in which etiology is uncertain and the intense antiinflammatory therapy applied within and following vitreoretinal surgery is emphasized.

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

In many parts of the world, parasitic infections of the eye are a major cause of blindness. The parasites Toxocara canis, Onchocerca volvulus, Taenia solium, Ancylostoma caninum, and Cysticercus celulosae all have been responsible for blinding ocular infections. The nematodes T. canis and Toxocara cati are parasitic roundworms that infect dogs (toxocarosis), other canidae, and cats. Ocular toxocariasis is an uncommon worldwide infection caused by the nematode larvae of T. canis, commonly found in dogs. Human transmission is usually via geophagia, the ingestion of food contaminated with Toxocara eggs, or contact with infected puppies, often resulting in devastating ocular or systemic effects. Ocular toxocariasis is typically a monocular disease of young children, and its clinical findings include posterior and peripheral retinochoroiditis, optic papillitis, and endophthalmitis. The inflammatory response created by ocular involvement may result in epiretinal membrane formation, traction retinal detachment, and combined traction-rhegmatogenous retinal detachment. Diffuse unilateral subacute neuroretinitis is another ocular parasitic infection that usually results in severe visual loss. Evidence suggests that diffuse unilateral subacute neuroretinitis is caused by a solitary unidentified nematode of two different sizes, but to date, only a small number of nematodes have been recovered from eyes affected with the infection. Diffuse unilateral subacute neuroretinitis occasionally can affect the fellow eye.

Ocular manifestations of systemic infections

Ocular involvement, mainly uveitis or retinochoroiditis, is common in various systemic diseases, such as endogenous endophthalmitis, Lyme disease, human T-cell lymphotropic virus type I infection, toxoplasmosis, and toxocariasis. Recent progress, especially in laboratory microbiologic testing, has enabled us to reliably diagnose many formerly idiopathic intraocular inflammatory diseases. A group of systemic infectious diseases, including those discussed here, are implicated as a body of emerging or re-emerging diseases that have appeared in the past two decades and are thought to have a close relation with global socioenvironmental changes. This paper discusses recent clinical and experimental studies of the most important systemic infectious diseases that affect the eye.