The Visual Field In Toxoplasma Chorioretinitis

Abstract

Abstract: : Purpose: An absolute indication for treatment of toxoplasma retinochoroiditis (TR) is the presence of lesions within one disc diameter of the optic nerve head, based on the assumption that these would lead to full thickness retinal loss with a resulting absolute scotoma breaking out to the periphery. We sought to test this assumption. Methods: A cross–sectional observational study of unselected cases of TR. Each affected eye had automated central visual field testing when their disease was quiescent. Results: 65 eyes were studied. 16 (24.6%) were excluded due to low quality (greater than 33% fixation losses, 20% false positives or 20% false negatives). Of the remaining 49 eyes, 47 eyes had a demonstrable central field defect; absolute defects were seen in 29 eyes (61.7%), of which 16 (55.2%) showed break out to the periphery, the remaining 13 (44.9%) remaining confined to the lesion. Relative field defects were detected in 18 (38.3%) eyes. For scars lying within 1 DD of the disc (n=9), 7/9 had an absolute defect with peripheral breakout; by contrast, of lesions outside this zone (n=40) an absolute defect with breakout was seen in 9 (p=0.02), without breakout in12, a relative defect in 17 and no defect in 2. Conclusions: This study supports the hypothesis that scars due to TR adjacent to the optic disc are significantly associated with absolute defects breaking out to the periphery compared to those lying outside this area. Whether treatment of these lesions affects the resulting field loss remains to be proven by clinical trial.

Keywords: toxoplasmosis • visual fields • chorioretinitis