The role of magnification correction in macular vessel density assessment: a contralateral eye study in anisometropia patients

BackgroundInvestigating the impact of magnification correction in macular vessel density using optical coherence tomography angiography (OCTA) in patients with anisometropia.MethodsCross-sectional study. Totally 47 patients (11 male, 36 female) aged >18 years with high myopia were analyzed. All patients underwent evaluation of visual acuity, subjective refraction, and axial length. Anisometropia (n=37) was defined as a refraction difference between paired eyes ≥0.75 D. The control group (n=10) consisted patients with a refraction difference ≤0.5 D. Superficial vessel density was performed using 3 mm × 3 mm Cirrus-HD OCTA protocol. The vessel length density (VLD) and foveal avascular zone area (FAZA) were analyzed before and after magnification correction using Bennett's formula.ResultsThe mean spherical equivalent (SE) was -10.54±3.47 D in the more myopic eye and -8.05±3.47 D in the contralateral eye (P<0.001). Before magnification correction, the mean perfusion density (PD) and VLD were both significantly lower in the more myopic eyes. After magnification correction, the VLD and PD did not differ between paired eyes. No statistical difference was found in terms of the FAZA between paired eyes regardless of magnification correction. The magnification-induced differences in both VLD and PD were positively correlated with the difference in SE (both r=0.86, P<0.001).ConclusionsIn OCTA analysis, magnification correction should be performed to reduce refraction error-induced image error, which deserves attention in the clinical application.