Abstract
Purpose :
Quantitative analysis of choriocapillaris in optical coherence tomography angiography (OCTA) has been mostly based on binary analysis of lighter versus darker pixels. Computerized texture analysis allows discrimination of higher-order patterns in image data, including inter-pixel correlation, skew, and coarseness. We investigated the application of this technique to OCTA images of choriocapillaris in normal subjects to extract quantitative metrics representing vascular patterns and perfusion in young healthy subjects.
Methods :
Observational cross-sectional study involving young healthy subjects with normal eye exam. RTVue-XR Avanti was used to obtain en-face 3x3mm images of superficial choriocapillaris. Computerized texture-analysis software was used to extract texture features in five categories: 1) Absolute value of gray levels, (average gray level, gray level yielding 70% threshold or 30% threshold of the area under the histogram; 2) gray-level histogram analysis, (balance and skewness); 3) spatial relationship among gray levels (coarseness, contrast, energy, entropy); 4) edge frequency (mean gradient as a function of distance between pixels); 5) fourier transform analysis (root-mean-square variation [RMS], first moment of power spectrum [FMP]). We stratified and compared the textural parameters between groups of age, sex, race and refractive error using a Student t-test and Bonferroni post-hoc test.
Results :
92 eyes of 47 subjects (12 men and 25 women), 28.8±5.99 yrs old were included. The mean and standard deviation from mean were measured to assess the distribution and dispersion of data points in each metric among eyes. There was a statistically significant difference in the following texture measures between races: gray level yielding 30% threshold (Caucasian group 1.43e2±6.28e0, African-American group 1.39e2±6.69e0, p=0.03), skewness (Caucasian 4.33e-2±9.33e-2, African-American 1.23e-1±1.13e-1, p=0.04) and RMS (Caucasian 3.16e7±1.35e6, African-American 3.08e7±1.42e6 p=0.04).
Conclusions :
Comparison of textural parameters revealed significant difference in certain parameters within race groups. This is the first OCTA image analysis to suggest a difference in retinal vascular patterns between healthy Caucasian and African-American subjects. This analysis may promise finding hidden vascular patterns not previously seen in OCTA imaging.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.