Eyesurgeryfoundation.com.au

By Dr Michael Wertheim, Ophthalmologist. Tel 9312 6033
Ocular toxoplasmosis should be considered in all patients who present with posterior ocular symptoms, especially immunocompromised patients. The Toxoplasma gondii (T. gondii) parasite has a complex lifecycle; the cat is the definitive host and intermediate hosts include pigs and sheep; humans most commonly contract the disease by ingesting uncooked meat containing Vertical transmission occurs when a pregnant may not be associated with a pigmented scar passes it on transplacentally. Congenital disease Recognising atypical forms of the disease tends to be more severe if acquired in the first can be challenging yet definitive diagnosis is trimester but transmission rates are highest essential before starting treatment. The best in the third trimester. Congenital disease way to make the diagnosis is by isolating T. manifests in many ways, from spontaneous gondii PCR from ocular fluid; by an anterior abortion to asymptomatic infants that present chamber tap or a vitreous biopsy. Blood levels later in life with ocular scarring or reactivation.
of T.gondii IgM antibodies may help; levels near the optic neve, and perhaps associated Making the diagnosis
rise during acute acquired toxoplasmosis and with an extensive vitritis or very decreased Symptoms may be non-specific and include the typically remain positive for less than a year. onset of new floaters, flashing lights, decreased (IgG antibodies remain positive for life but are A 2002 survey of 78 American Uveitis Society non-specific because a high proportion of the specialists revealed 24 different regimens using Ophthalmic examination is often all that is population has a positive IgG for non-ocular 9 different parasitic drugs. Only 17% used an oral corticosteroid when treating all cases of The appearance of unilateral active retinal Treatment
toxoplasmosis is classic (Figure 1). Re-activated patients while others used corticosteroid only lesions have a pigmented area (old scar) status of the patient and location of the lesion for specific indications. So agreement on the associated with an adjacent fluffy white lesion in the retina. All immunocompromised patients ideal treatment is debatable and contentious. (active lesion). There is usually a single lesion combination of pyramenthamine, sulphadiazine, In immunocompetent patients, the disease clindamycin and prednisolone. Currently, an is usually self-limiting and, if not sight- effective treatment is a course of azithromycin signs are non-specific and may be confused threatening, can be closely monitored in clinic. alone, with or without prednisolone.
with other retinal inflammation or infection; However, all sight-threatening lesions need This clinical update is supported by the Eye Surgery multiple lesions may be bilateral and may or treatment; lesions within the temporal arcades, medicalforum

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