Relationship Between Funduscopic Conus and Optic Disc Factors Associated with Myopia in Young Healthy Eyes

To determine the relationship between funduscopic findings in myopic eyes and the prevalence and structure of the conus in the optical coherence tomographic (OCT) images.

A prospective observational cross-sectional study of 121 right eyes of 121 young healthy volunteers. All participants underwent color fundus photography (CFP), scanning laser ophthalmoscopy, and OCT. Based on the OCT analyses, the area between the edge of the ellipsoid zone (EZ) and that of choroid was defined as the "choroidal conus (CC)", and the area between the edge of the choroid and the scleral edge as the "scleral conus (SC)". The eyes were classified into three groups such as the non-conus (NC) group, CC group, and SC group. The differences in the axial length, optic disc tilt, ovality ratio, papillomacular position angle, and peripapillary nerve fiber elevation (pNFE) between the three groups were determined.

CFPs detected a conus in 79 eyes (65.3 %). The outer border of the conus in CFPs corresponded with the edge of the EZ in the OCT in all subjects. Thirty-seven eyes had CC alone (CC group) and 42 eyes had both CC and SC (SC group). The CC and SC groups had longer axial lengths and more frequent pNFEs than the NC group. There was a significant difference in the optic disc tilt and ovality ratio between the CC and SC groups.

The eyes with SC tend to have larger optic disc tilt and smaller ovality ratio than the eyes with CC only.