The influence of magnification correction on macular retinal/choroidal thickness and vessel density measurements using optical coherence tomography angiography in 4-17-year-old students.

BACKGROUND

Transverse macular measurements from optical coherence tomography angiography (OCTA) depend on ocular magnification, which varies with axial length (AL); in growing children, whether correcting for magnification alters macular thickness and vessel-density measurements enough to matter clinically is unclear, and no anchor-based clinical threshold exists.

METHODS

In this cross-sectional study, retinal and choroidal thickness (RT, ChT) and retinal and choroidal vessel density (RVD, CVD) -each in the central fovea, parafovea, perifovea and whole-grid average (16 parameters) -were measured before and after magnification correction in 339 children and adolescents aged 4-17 years (central 6 × 6 mm macula, swept-source OCTA [SS - OCTA]); vessel length density (VLD) and matched superficial retinal vessel density (SRVD) were also compared. Clinical relevance was tested against a distribution-based 0.5 × standard deviation (SD) threshold by equivalence testing, and the correction difference was modelled across AL.

RESULTS

Correction produced statistically detectable changes in many parameters, but the mean difference for all 16 parameters lay within ±0.5 × SD (population-level equivalence). Only perifoveal and average RT crossed the threshold, at the extremes of AL (< 21.4 or > 26.6 mm and > 27.7 mm, respectively); choroidal thickness and areal vessel density were essentially unaffected (relative change ≤ 0.3%). In contrast, VLD scaled inversely with the magnification factor and crossed the threshold within the observed range (AL 〈 22.3 or 〉 25.7 mm; 11.5% of eyes), whereas SRVD crossed nowhere. The AL-RT association weakened after correction; vessel density related mainly to age.

CONCLUSION

In this pediatric cohort, magnification correction was clinically important chiefly for retinal thickness in very short or very long eyes and for vessel length density outside AL 22.3-25.7 mm; choroidal thickness and areal vessel density were little affected. A parameter's need for correction is thus set by its dimensions. Age should also be considered when interpreting macular microvasculature in children.