Appropriate lateral scaling of optical coherence tomography-angiography (OCT-A) images based on axial length (AL) measurements improves accuracy in foveal avascular zone (FAZ) measurements in pediatric patients, according to a study published in Optometry and Vision Science.
Researchers conducted an analysis to determine how AL changes over time affect estimates of FAZ area change in OCT-A images. They included 20 children younger than18 years and 40 adults (mean age, 28±17.23 years, 77% women or girls) in the study. Investigators obtained AL measurements at 2 time points, along with 2 FAZ segmentations at each time point via OCT-A imaging. They estimated FAZ area at both time points through 2 methods; assumed/fixed axial length of the OCT-A device (unscaled), and by using the participant’s AL (scaled). Mean follow-up time for the pediatric group was 3.35±1.66 years compared with 2.90±1.65 years for the adult group.
Researchers found that FAZ area appeared to decrease between visits in the pediatric group (P =.004) and increase in the adult group (P =.003) when using unscaled data. After using correctly scaled means, they confirmed that FAZ area did increase between visits in the adult group (P <.001), but did not have a significant change between visits for the pediatric group (P =.37). Once investigators compared normalized FAZ area change across visits between unscaled and scaled data, they observed a significant difference between the adult and pediatric groups (P <.001).
“We have shown that not accounting for axial length in a pediatric population over time can result in incorrect conclusions regarding both the direction and magnitude of changes in foveal avascular zone morphometry (as well as errors in absolute foveal avascular zone measurements, as has been shown previously),” according to the researchers. “As retinal imaging becomes progressively more common in younger populations, it is critical that accurate methods to account for eye growth (and therefore changes in lateral scale of retinal images) are developed and followed.”
Study limitations include an overrepresentation of women and girls, small sample size, and failure to include ocular biometry measurements other than AL.
Disclosure: Funding was provided by Optomvue, AGTC, and MeiraGTx. Translational Imaging Innovations also declared an equity interest in the research. Please see original reference for a full list of authors’ disclosures.
Linderman RE, Heffernan E, Ferrante S, Bachman Groth J, Carroll J. The Impact of Axial Eye Growth on Foveal Avascular Zone Measurements in Children. Optom Vis Sci. 2022;99(2):127-136. doi:10.1097/OPX.0000000000001854