Parapapillary Βbm and Γ Zones Played Different Roles in Axial Elongation among Young Adolescents Using Optical Coherence Tomography

PURPOSE. To evaluate the influencing factors of parapapillary beta(BM) and gamma zones incidence in young adolescents and to explore their associations with axial length progression. METHODS. In this prospective cohort study, 976 seventh-grade students from nine secondary schools in Beijing, China, were enrolled and followed up 1 year later. Parapapillary beta(BM) zone was defined as retinal pigment epithelium loss while Bruch's membrane was present. Parapapillary. zone was defined as the absence of retinal pigment epithelium and Bruch's membrane. Logistic regression model was used to analyze the influencing factors of beta(BM) and gamma zone incidence. A linear mixed model was used to analyze the associations between parapapillary zones and axial elongation. RESULTS. Of the 976 participants, 139 (14.2%) had only beta(BM) zone, 398 (40.8%) had only gamma zone, and 171 (17.5%) had both. At follow-up, the incidence of beta(BM) zone was 11.5% (76/659), and the incidence of gamma zone was 9.7% (39/404). Optic disc tilt, thinner subfoveal choroid, and longer axial length at baseline showed a higher risk of gamma zone incidence. The absence of gamma zone at baseline showed a faster axial length progression. When the baseline axial length was 25 mm or longer, the beta(BM) zone was also related to the axial elongation. CONCLUSIONS. The gamma zone was associated with axial length progression, and the beta(BM) zone was also associated with the axial length progression when the axial length exceeded 25 mm, which was consistent with the notion that excessive axial length growth not only is the extension of the eyeball but also has its own pathologic changes.