RESUMO
PURPOSE: Diagnosis of congenital optic nerve hypoplasia (CONH) can be challenging in children or uncooperative individuals. Misdiagnosis can lead to inappropriate treatment; thus, it is important to identify an objective and reliable measurement. The purpose of this study was to evaluate whether Cirrus spectral domain optical coherence tomography (SD-OCT) is a valid test for diagnosing CONH by comparing it to the disc-macula distance to disc diameter (DM:DD) ratio. METHODS: A total of 93 participants (64 controls and 29 CONH) underwent comprehensive eye examinations, fundus photography and Cirrus SD-OCT. Receiver operating characteristic (ROC) curves for the DM:DD ratio and OCT disc area were constructed for CONH and control eyes. RESULTS: Mean (±SD) OCT disc area was 1.46 (±0.42) mm2 and 1.89 (±0.38) mm2 for CONH and control eyes, respectively (p < 0.0001). The area under the curve for the DM:DD ratio was 0.97 (95% confidence interval: 0.91-0.99) and 0.79 for OCT disc area (95% confidence interval: 0.70-0.86), which were significantly different (p = 0.0005). The optimal cut-off value for OCT disc area was 1.66 mm2 (76% sensitivity, 70% specificity), while the optimal cut-off for DM:DD ratio was 3.10 (85% sensitivity and 95% specificity). The Cirrus SD-OCT showed a tendency to overestimate disc size, especially in cases with no light perception (NLP) or segmental CONH. CONCLUSIONS: Although the DM:DD ratio is superior to OCT in diagnosing CONH with a higher sensitivity and specificity, the ratio is subject to inter-examiner variability and can be challenging to obtain. We found the Cirrus SD-OCT to be a valid objective test for diagnosing CONH. Caution is advised when using SD-OCT in segmental CONH or in an eye with NLP. We suggest 1.66 mm2 as the optimal cut-off value for Cirrus SD-OCT disc area to differentiate a hypoplastic from a normal optic disc.
