Retinal Review, Issue 06
CASE NUMBER 6
A 15 year old Chinese girl was referred for vision loss in her left eye. She first noted trouble with her vision six months before. She went to another eye doctor who suggested observation and the vision remained blurred. Past ocular history is significant for moderate myopia. Medical history is noncontributory. Entering vision was OD: 20/20 and OS: 20/100. Applanation tensions were normal. The anterior segments were quiet OU. Amsler grid was full OD and showed a central scotoma OS. The lenses and vitreous cavities were clear. Dilated examination of the right eye was normal. In the left eye there was a macular defect. The periphery was normal. Fluorescein angiography demonstrated staining of the lesion with mild late leakage.
A pigmented scar was noted in the left macula. The scar appeared inactive but late fluorescein leakage suggested that there was mild activity. The concern was that there was a chronic choroidal neovascular membrane (CNVM) with mild persistent leakage. It is unusual for young patients to have a CNVM. Etiologies can include previous chorioretinitis, POHS, trauma, myopia, angioid streaks, or idiopathic. We initially diagnosed the patient with a chronic idiopathic CNVM and after a discussion with the family elected to proceed with antiVEG-F injections. The patient had two Avastin injections a month apart and returned with improved vision. Although a central scotoma was still present the acuity improved to 20/60 and leakage was no longer noted on angiography:
With the happy feeling of having helped a patient with her vision, we contentedly dismissed her and recommended a two month follow up. To our surprise the patient returned one month later with vision loss OS. Acuity was once again 20/100 but a new finding was present:
It turned out that our initial diagnosis was incorrect. The chorioretinal scar was not a mildly active CNVM – it was a scar from a previous bout of toxoplasmosis retinochoroiditis. This was surprising for a number of reasons: First, the patient was from China and moved to America 5 years before presentation. Toxoplasmosis is endemic in South and Central America, but rare in Asia. Second, toxoplasmosis scars are typically larger and more peripheral. This scar was small and central. Third, the scar responded to Avastin – which in retrospect was likely because it was still somewhat active and leaking. Finally, toxoplasmosis usually is accompanied by significant ocular inflammation – her eye was white and quiet throughout. The patient has an unusual variant of toxoplasmosis called “Outer Retinal Toxoplasmosis”. In this variant the lesion is smaller than average, usually within the macula, and not accompanied by significant inflammation. Treatment is with oral antibiotics and steroids. We started her on double strength bactrim and prednisone. By her next visit two weeks later vision had improved to 20/40. The lesion gradually scarred and she was left with a stable perifoveal scar. The issue going forward is the potential for further episodes. With each recurrence the scar can enlarge and the scotoma can progress. Recurrences are unpredictable and unpreventable.