Age and gender influence on foveal avascular zone in healthy eyes.

The foveal avascular zone (FAZ) is the capillary-free area in the central macula with high photoreceptor density and metabolic activity. In the present study we measured the superficial and deep macular foveal avascular zone (sFAZ, dFAZ) in the eyes of healthy adults of both sexes of various ages ranging from 10 to 69 years using optical coherence tomography angiography (OCT-A) in order to evaluate the influence of gender and age on FAZ size. A cross-sectional study was carried out in 240 eyes of 120 healthy subjects, OCT-A was performed by means of a Topcon swept source OCT. sFAZ and dFAZ areas were measured using the IMAGEnet6 software package. Subjects were grouped by age (six groups) and gender. The mean ±â€¯sd age of the subjects was 39.2 ±â€¯17.4 years (50% women, 50% men), ranging from 10 to 69 years. The overall mean sFAZ size in women (0.297 ±â€¯0.110 mm2) was significantly larger (p = 0.002) than in men (0.254 ±â€¯0.098 mm2). Similarly, the overall mean dFAZ in women (0.322 ±â€¯0.111 mm2) was significantly larger (p < 0.001) than in men (0.273 ±â€¯0.099). However, when analyzed by age group, these gender differences appeared only in groups younger than 20 years old and older than 50 years old. Men did not show differences among the six age groups. In women, for both sFAZ and dFAZ, the 20-29 year old group had a smaller FAZ size than the 50-59 year old group. In conclusion for both sFAZ and dFAZ, women have larger areas than men, but this occurs only in the young and old age groups. In men, age does not seem to influence the size of the FAZ, but in women, both sFAZ and dFAZ were significantly smaller in younger than in older ages. These results suggest that retinal changes in retinal structure caused by aging may be different in woman than in men, probably reflecting the more hormonal variations known to exist with age in women.

Automatic segmentation of the foveal avascular zone in ophthalmological OCT-A images.

Angiography by Optical Coherence Tomography (OCT-A) is a non-invasive retinal imaging modality of recent appearance that allows the visualization of the vascular structure at predefined depths based on the detection of the blood movement through the retinal vasculature. In this way, OCT-A images constitute a suitable scenario to analyze the retinal vascular properties of regions of interest as is the case of the macular area, measuring the characteristics of the foveal vascular and avascular zones. Extracted parameters of this region can be used as prognostic factors that determine if the patient suffers from certain pathologies (such as diabetic retinopathy or retinal vein occlusion, among others), indicating the associated pathological degree. The manual extraction of these biomedical parameters is a long, tedious and subjective process, introducing a significant intra and inter-expert variability, which penalizes the utility of the measurements. In addition, the absence of tools that automatically facilitate these calculations encourages the creation of computer-aided diagnosis frameworks that ease the doctor's work, increasing their productivity and making viable the use of this type of vascular biomarkers. In this work we propose a fully automatic system that identifies and precisely segments the region of the foveal avascular zone (FAZ) using a novel ophthalmological image modality as is OCT-A. The system combines different image processing techniques to firstly identify the region where the FAZ is contained and, secondly, proceed with the extraction of its precise contour. The system was validated using a representative set of 213 healthy and diabetic OCT-A images, providing accurate results with the best correlation with the manual measurements of two experts clinician of 0.93 as well as a Jaccard's index of 0.82 of the best experimental case in the experiments with healthy OCT-A images. The method also provided satisfactory results in diabetic OCT-A images, with a best correlation coefficient with the manual labeling of an expert clinician of 0.93 and a Jaccard's index of 0.83. This tool provides an accurate FAZ measurement with the desired objectivity and reproducibility, being very useful for the analysis of relevant vascular diseases through the study of the retinal micro-circulation.