Evaluating retinal vessel diameter with optical coherence tomography in normal-tension glaucoma patients

Purpose To investigate a novel optical coherence tomography (OCT)-derived variable, circumpapillary mean retinal shadow width (cpMRSW), and to elucidate its association with normal-tension glaucoma (NTG). Methods For the purpose of validation, we measured retinal vascular calibers in 68 arterioles and 100 venules of 12 NTG patients and 12 healthy subjects and compared the width of the visible retinal shadows in spectral-domain OCT images and the caliber of retinal vessels in retinal photographs. Then we calculated cpMRSW in 78 NTG eyes and 25 age-matched healthy control eyes. Additionally, we divided the patients into early (mean deviation: MD > −6 dB), moderate (MD −6 to −12 dB), and severe (MD < −12 dB) NTG groups, and compared cpMRSW in these groups. Finally, we calculated the area under the receiver operating characteristic (ROC) curve in order to determine the power of mean retinal shadow width to distinguish the groups. Results OCT retinal shadow width was significantly correlated with photography-measured retinal caliber ( r = 0.82, P < 0.001). CpMRSW was significantly different between the control and NTG patients (control: 107.3 ± 7.0 µm, mild: 99.4 ± 8.6 µm, moderate: 99.7 ± 9.5 µm, severe: 90.5 ± 12.0 µm, P < 0.001), despite similar distributions in systemic variables. An ROC analysis revealed that cpMRSW could differentiate NTGs from normal eyes (area under the ROC curve: 0.81). Conclusions Our new software for measuring mean retinal shadow width in OCT images may be a valuable tool for detecting NTG and diagnosing its severity.