It is reported that it takes a period form 22 weeks pregnant to the first 45 months of life for macular region to develop from structural formation to functional integrity. However, children are still in the critical period of plastic visual development, for their visual acuity has not yet reached the level of adults. Similarly macular retinal structure may develop with age. It is very important to study in macular thickness of this period and to have a proper cognition of it and the relation between macular thickness and other ocular parameter for the research of retinal development and diseases and the early screen of fundus diseases.

It is reported that it takes a period form 22 weeks pregnant to the first 45 months of life for macular region to develop from structural formation to functional integrity. However, children are still in the critical period of plastic visual development, for their visual acuity has not yet reached the level of adults. Similarly macular retinal structure may develop with age. It is very important to study in macular thickness of this period and to have a proper cognition of it and the relation between macular thickness and other ocular parameter for the research of retinal development and diseases and the early screen of fundus diseases.

Optical Coherence Tomography (OCT) is an imaging technique widely used in clinic in last twenty years. According to the base theory of dim coherent light interference machine, OCT detect the back-reflection or scattering signal of biological tissue to the incident dim coherent light, and acquire the two-dimension or three- dimension image of biological tissue by scan. It enables the characteristic of tissue's microstructure in vivo and makes it possible to observe dynamically developing process of diseases so that it has become an essential test for macular and optic nerve diseases with unmatched measurement reproducibility. It also enables high-resolution and noninvasive imaging of the retinal lamina, the organizational structure of macular. It is most often used clinically to demonstrate the macular morphology, treatment response and disease progression clinically. However, who researchers studyed in through OCT were mostly patients with retinal disease and adults. There was few study focused on OCT's application to children.

In this study, the investigators aims to measure macular thickness (MT) using spectral-domain optical coherence tomography (SD-OCT) and to investigate MT variations with sex, age, laterality, refraction error (RE) and axial length (AL).

Inclusion Criteria:

• age from 4 to 17 years
• children with the mild-to-moderate refraction error(from 0 to -6.00D)

Exclusion Criteria:

• children with visual complaints

Subjects consisted of Zhongshan Ophthalmic Center (ZOC) and Hualong Primary School (HPS)), who came from ZOC group were mild-to-moderate refraction error while who come from HPS group had no visual complaints.