This was a cross-sectional, prospective, observational study. One hundred thirty-three eyes of 133 volunteers were examined between November 1, 2010 and February 20, 2012. The volunteers did not have any eye diseases as determined by examining their medical records and our ophthalmologic examinations. Only the data from the right eyes were statistically analyzed. The eligibility criteria were: aged 20 years or older, but 40 years or younger; eyes normal by slit–lamp biomicroscopy, ophthalmoscopy, and OCT; best-corrected visual acuity of greater than or equal to 0.1 logMAR units; and IOP less than or equal to 21 mm Hg. The exclusion criteria were: eyes with known ocular diseases such as glaucoma, staphyloma, and optic disc anomaly; known systemic diseases such as hypertension and diabetes; presence of visual field defects; and prior refractive or intraocular surgery. None of the eyes was initially excluded because of poor OCT image quality caused by poor fixation. Three eyes were excluded due to a superior segmental optic disc hypoplasia, one eye was excluded due to glaucoma, and three eyes were excluded because of prior refractive surgery. Nine other eyes were excluded because of a disagreement on the presence of a pNFE between two raters. In the end, the right eyes of 117 individuals (80 males and 37 females) were used for the analyses.