Purpose To categorize visual field (VF) defects according to Freitag and Tanking's (FT) classification in Thyroid Eye Disease-Compressive Optic Neuropathy (TED-CON) and evaluate the interreader agreement and intrareader reproducibility of the classification. Subjects and methods In this retrospective, observational study we included medical reports of 96 eyes (51 patients), who underwent VF testing with TED-CON in Ludwig-Maximilians-University (2008-2019). Two readers separately examined the VFs at the time of the TED-CON diagnosis, each offering two readings of the same VF in a time interval of 1 month. None of our patients were diagnosed with only VF testing. The visual field testing was only performed when the inclusion criteria for TED-CON were met. Results The most common VF defects upon TED-CON diagnosis were stage 1b defects in FT classification (34.4% for reader 1, 35.4% for reader 2), followed by stage 2b (10.4% for reader 1, 14.6% for reader 2), and stage 3 (10.4% for both readers). The overall interreader agreement between 2 examiners was substantial for the first reading (69.8% agreement, kappa 0.635 (95% CI [0.525-0.745])) and moderate for the second reading (66.7% agreement, kappa 0.598 (95% CI [0.488-0.708])). The intrareader reproducibility ranged from substantial to almost perfect (78.1% agreement) between readings (kappa 0.736 (95%CI [0.638-0.834])) for reader 1 and 90.6% agreement (kappa 0.885 (95%CI [0.814-0.956])) for reader 2. Conclusion We found good BCVA (LogMAR <= 0.2), in nearly half of the cases (44 eyes, 45.8%) and also, strikingly near perfect visual acuity (BCVA LogMAR <= 0.1) in 22.9% of the cases (22 eyes) with TED-CON. We conclude that clinicians should be alert to VF defects in the inferior region (stage 1a/1b in the FT classification) even in patients with a good BCVA.
