Prevalence and Characteristics of Peripapillary Gamma Zone in Children with Different Refractive Status: The Hong Kong Children Eye Study

Abstract

PURPOSE. This study aimed to assess the prevalence and characteristics of the peripapillary gamma zone in myopic, emmetropic, and hyperopic eyes of Chinese children. METHODS. Overall, 1274 children aged 6 to 8 years from the Hong Kong Children Eye Study underwent ocular examinations, including measurements of cycloplegic auto-refraction and axial length (AL). The optic disc was imaged using a Spectralis optical coherence tomography (OCT) unit and a protocol involving 24 equally spaced radial B-scans. The Bruch’s membrane opening (BMO) was identified in over 48 meridians in each eye. The peripapillary gamma zone was defined as the region between the BMO and the border of the optic disc, identified by the OCT. RESULTS. The prevalence of the peripapillary gamma zone was higher in myopic eyes (36.3%) than in emmetropic (16.1%) and hyperopic eyes (11.5%, P < 0.001). AL (per 1 mm; odds ratio [OR]) = 1.861, P < 0.001) and a more oval disc shape (OR = 3.144, P < 0.001) were associated with the presence of a peripapillary gamma zone after adjusting for demographic, systemic, and ocular variables. In the subgroup analysis, a longer AL was associated with the presence of a peripapillary gamma zone in myopic eyes (OR = 1.874, P < 0.001), but not in emmetropic (OR = 1.033, P = 0.913) or hyperopic eyes (OR = 1.044, P = 0.883). A peripapillary zone was not observed in the region nasal to the optic nerve in myopic eyes, in contrast to its presence in the same region in 1.9% of emmetropic eyes and 9.3% of hyperopic eyes; these intergroup differences were statistically significant (P < 0.001). CONCLUSIONS. Although peripapillary gamma zones were observed in the eyes of both myopic and non-myopic children, their characteristics and distribution patterns were substantially different.