PurposeTo follow choroidal thickness (ChT) over time in birdshot retinochoroiditis (BRC) using enhanced depth imaging optical coherence tomography (EDI-OCT) and study the effect of early and sustained treatment on ChT.Patients and methodsEighteen patients were included and EDI-OCT measurements of ChT were analyzed retrospectively in five groups of patients with follow-up times ranging from 1 year to ≥15 years. The OCT images were evaluated and ChT was calculated under the foveola and 1500 μm temporal, nasal, superior, and inferior to the foveola. To assess the effect of treatment, 13 patients with a disease duration ≥10 years were divided into two groups depending on their treatment status: early and sustained therapy vs insufficient, late, or no treatment. ChT was compared in these two groups along with the number of typical fundus BRC lesions.ResultsThe ChT decreased (r=-0.41, P=0.0018) over the disease duration, which ranged from <1 year to ≥15 years. In patients with a disease duration ≥10 years, a significant difference in ChT was noted between adequately and undertreated patients (288.3±76.9 μm vs 161.4±39.2 μm; P=0.004). At the last follow-up, in the group with insufficient therapy 10 of 11 eyes presented typical fundus BRC lesions vs 2 of 13 eyes in the treated group (P≤0.0006, F-test).ConclusionsChoroidal thickness decreases significantly over time in BRC. If undertreated, patients show thinner choroids compared with adequately treated individuals and present significantly more BRC lesions.