Purpose: To describe the clinical findings and course of toxoplasmic anterior optic neuropathy and to differentiate primary and secondary involvement.
Methods: Retrospective observational case series from a tertiary referral institution. Clinical and photographic charts of 13 patients with toxoplasmosis with direct optic nerve head involvement were reviewed and data were collected throughout the length of follow-up.
Results: Toxoplasmic anterior optic neuropathy was divided into two types. Type I was defined as secondary infectious involvement of the optic nerve head from an adjacent focus of chorioretinitis that resolved with chorioretinal scarring. Type II was defined as primary involvement of the optic nerve head that resolved without chorioretinal scarring. Visual acuity improved after treatment in both Type I and Type II patients; however, the visual prognosis was worse in Type I patients due to macular involvement. Eighty-three percent of Type II patients had a final visual acuity equal to or better than 20/25 compared to 50% of Type I patients. Visual field defects were present in all patients, most frequently arcuate or altitudinal (62%). Delay in diagnosis was common (54%), especially in Type II patients (71%). Vitreous inflammation was absent on the initial examination in 31% of the patients.
Conclusion: Toxoplasmic anterior optic neuropathy is an uncommon manifestation of ocular toxoplasmosis. Delays in diagnosis are common because of the frequent lack of typical chorioretinitis or vitreous inflammation. Adjacent macular involvement strongly influences visual outcome.