2020–2021 BCSC Basic and Clinical Science Course™
12 Retina and Vitreous
Part II: Disorders of the Retina and Vitreous
Chapter 11: Focal and Diffuse Choroidal and Retinal Inflammation
Infectious Retinal and Choroidal Inflammation
Toxocariasis is a parasitic infection caused by 1 of 2 roundworms: Toxocara canis or Toxocara cati, which are common intestinal parasites of dogs and cats, respectively. Humans are infected following ingestion of soil or vegetables contaminated by the ova. Although ocular toxocariasis is part of a systemic infestation by the nematode, systemic manifestations such as visceral larval migrans, fever, and eosinophilia are relatively uncommon. Children and young adults are affected disproportionately. Common symptoms include decreased vision and floaters. The condition is unilateral in most cases and typically has 1 of 3 presentations: (1) a peripheral granuloma, which often produces a traction band that extends toward the macula (Fig 11-23) and occasionally mimics unilateral intermediate uveitis with snowbank formation; (2) a posterior pole granuloma, which can decrease vision dramatically when the central macula is involved; or (3) a moderate to severe panuveitis that can mimic endogenous endophthalmitis. Enzyme-linked immunosorbent assay (ELISA) analysis of serum or intraocular fluids can help establish the diagnosis in these cases but is relatively insensitive. Vitreous inflammation, CME, and tractional retinal detachment are the most common causes of vision loss. Most specialists assume that the uveitis of toxocariasis represents an immune response to antigens released from a dead or dying worm. Thus, treatment typically involves use of local or systemic corticosteroids, and antihelminthic therapy has little or no therapeutic role.
Figure 11-23 Color fundus photograph from a 6-year-old boy with reduced and distorted vision. The image shows a peripheral toxocariasis cyst with associated fibrosis (bottom left). The fibrosis results in considerable traction, and the macula is dragged inferiorly and distorted.
(Courtesy of Colin A. McCannel, MD.)
Woodhall D, Starr MC, Montgomery SP, et al. Ocular toxocariasis: epidemiologic, anatomic, and therapeutic variations based on a survey of ophthalmic subspecialists. Ophthalmology. 2012;119(6):1211–1217.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.