Comparison of Cirrus spectral domain OCT with disc-macula distance to disc diameter ratio in diagnosing congenital optic nerve hypoplasia

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) mm(2) and 1.89 (+/- 0.38) mm(2) 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 mm(2) (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 over-estimate 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 mm(2) as the optimal cut-off value for Cirrus SD-OCT disc area to differentiate a hypoplastic from a normal optic disc.

Automated summary

The purpose of this study was to evaluate the effectiveness of Cirrus spectral domain optical coherence tomography (SD-OCT) in diagnosing congenital optic nerve hypoplasia (CONH) compared to the disc-macula distance to disc diameter (DM:DD) ratio. The study found that the DM:DD ratio was superior to OCT in diagnosing CONH with a higher sensitivity and specificity. However, the ratio is subject to inter-examiner variability and can be challenging to obtain. The study concluded that Cirrus SD-OCT is a valid objective test for diagnosing CONH, but caution is advised when using it in segmental CONH or in cases with no light perception (NLP). The optimal cut-off value for Cirrus SD-OCT disc area to differentiate a hypoplastic from a normal optic disc was suggested to be 1.66 mm2.