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.

Visualizing of skin chromophore concentrations by use of RGB images.

A method is proposed for visualizing simply the concentrations of melanin, oxygenated blood, and deoxygenated blood in skin tissue using digital RGB images. The total blood concentration and oxygen saturation can also be reconstructed. Monte Carlo simulation of light transport specifies a relation between the chromophore concentrations and Commission Internationale de l'Eclairage XYZ, which are compatible with the common RGB working space. Experiments with a tissuelike agar gel phantom demonstrated the possibility of the method. In vivo imaging of a human hand during forearm occlusion demonstrated the ability of the method to evaluate hemodynamics of skin tissue.