Diagnostic Ability of Barrett's Index and Presence of Intracranial Fat Prolapse in Dysthyroid Optic Neuropathy.

Measurement of BI is a simple diagnostic method for detecting DON in Thai populations. The presence of fat prolapse (2.5 mm) provides a lower sensitivity compared with a BI at 40%. A slightly larger BI or fat prolapse should be suspected of DON for early treatment.