Two-dimensional Peripheral Refraction and Retinal Image Quality in Emmetropic Children

The relationship between the optical properties of the eye in the periphery and myopia development is still under debate. To further clarify this issue, we provide here baseline data of two-dimensional peripheral optics results in a group of emmetropic Chinese children. Peripheral aberrations were measured under cycloplegia by using an open-view Hartmann-Shack wavefront sensor (VPR, Voptica SL, Spain). This instrument allows to measure fast in the horizontal visual field from temporal 30 degrees to nasal 30 degrees every 1 degrees. Two-dimensional (2D) maps were retrieved from a series of horizonal scans taken every 4 degrees from 20 degrees superior to 16 degrees inferior covering a visual field of 60 x 36 degrees. A relatively homogeneous pattern of the 2D relative peripheral refraction was found across all these emmetropic subjects. Using cluster analysis followed by manual visual refinement, the 2D maps were identified to fit into four categories. More than 70% of the subjects showed a nearly flat horizontal refraction with a slightly myopic shift in the superior retina. Peripheral astigmatism was quite constant across subjects and similar to that expected theoretically. Peripheral aberrations were also similar to those in the fovea for a large retinal area. These baseline data would offer an important reference to compare with the future evolution with time, as well as with other refractive or age groups of subjects, to better understand the role of peripheral optical properties in myopia development.