Abstract
Purpose: :
To correlate retinal vessel thickness (RVT) measurements with circumpapillary Retinal Nerve Fiber Layer (RNFL) in healthy volunteers.
Methods: :
A sample of 32 healthy volunteers underwent complete ophthalmologic examination, including HR-OCT scanning (Cirrus® Carl Zeiss Meditec Inc.) and RNFL Assessment (GDx-ECC ® Carl Zeiss Meditec Inc.). The RVT profile of each patient was determined in the respective SLO image provided by HR-OCT, centered in the optic disc (OD)(816 pixels high by 977 pixels width). A specially designed proprietary software developed in MATLAB® (Version R2009b, The Mathworks Inc.) was used for manual identification of the OD contour and measurement of the RVT at 50 pixels distance from the OD contour.The angle at the OD center between a line from the OD center to measurement point of the retinal vessel and a horizontal line was calculated. The RVT values were assigned to 64 specified intervals of angles to facilitate the correlation with the 64 RNFL thickness values of GDx-ECC. The RVT data was convolved with a Gaussian window of size 16, in order to generate a circumpapillary RVT profile. Each RVT profile was correlated with the respective RNFL thickness profile around the OD, using SPSS Software Package (version 17.0).
Results: :
26 of the 32 volunteers presented significant Pearson correlations (p<0.05), ranging between 0.21 and 0.91, with a mean value of 0.55 (standard deviation of 0.22) and a 25 and 75 percentiles of 0.35 and 0.78, respectively. The R-square value of the correlation coefficient was 0.3025.
Conclusions: :
The correlations between RVT and RNFL profiles around the OD, found for healthy volunteers, suggest that the individual RVT profile contains, on average, approximately 30% of the individual RNFL profile information. The circumpapillary RVT profile might be a good predictor for the circumpapillary RNFL thickness profile. These results support the theory that independent retinal biomarkers might be useful for compensation of the intersubject variability of healthy circumpapillary RNFL thickness.
Keywords: imaging/image analysis: clinical • nerve fiber layer