The Impact of Axial Eye Growth on Foveal Avascular Zone Measurements in Children

Abstract

SIGNIFICANCE Foveal avascular zone (FAZ) area is a frequently used biomarker in diseases impacting the retinal vasculature in pediatric populations. Variation in axial length between individuals results in differences in lateral image scale, which affect the accuracy of FAZ area measurements. Accordingly, changes in axial length over time within individual children would affect estimates of FAZ area change. PURPOSE This study aimed to quantify how changes in axial length over time affect estimates of FAZ area change using optical coherence tomography angiography (OCT-A) images. METHODS Twenty pediatric participants (<18 years old) and 40 adult participants were imaged on Optovue's Avanti system (Fremont, CA) and had axial length measurements acquired at two time points. The FAZ was segmented twice using the OCT-A image at each time point. Foveal avascular zone area was estimated at both time points using the assumed/fixed axial length of the OCT-A device (unscaled) and using the participant's axial length (scaled). Changes in FAZ area over time were compared between the pediatric and adult groups using both unscaled and scaled data. RESULTS The average ± standard deviation follow-up time was 3.35 ± 1.66 years for the pediatric group and 2.90 ± 1.65 years for the adult group. Using unscaled data, FAZ area seemed to decrease between visits in the pediatric group ( P = .004), whereas the FAZ area increased between visits in the adult group ( P = .003). When correctly scaled data were used, the FAZ area still increased between visits for the adult group ( P < .001), although the FAZ area no longer showed a significant change between visits for the pediatric group ( P = .37). When comparing the normalized FAZ area change across visits between unscaled and scaled data, a significant difference was found between the adult and pediatric groups ( P < .001). CONCLUSIONS Scaled data should be used when measuring FAZ area in pediatric populations, especially in longitudinal studies.

Correction Method for Optical Scaling of Fundoscopy Images: Development, Validation, and First Implementation

“…The PAROS method could be extended to these types of imaging modalities, but doing so would require further validation to ensure accurate mathematical description of the camera. Interestingly, various OCT studies report a similar variation (up to 25% 41 , 42 ) of image scaling as found in this study ( Fig. 6 A), suggesting a similar clinically relevant impact of correcting for magnification differences.…”

Quantification and Predictors of OCT-Based Macular Curvature and Dome-Shaped Configuration: Results From the UK Biobank

“…22 , 28 , 29 A recent paper showed a reversal of correlation between foveal avascular zone and aging in children by correction for axial length in this context. 47 However, the lateral distortion in our images should have led to fewer (positive or negative) curvature measures in longer eyes and vice versa in shorter eyes and should not have changed the direction of the curvature. It therefore should not alter the main conclusions of our analysis.…”