Example of retinal nerve fiber layer (RNFL) analysis with spectral-domain optical coherence tomography (SD-OCT). Top: The right eye shows diffuse RNFL thinning on SD-OCT (A), which is consistent with the neuroretinal rim thinning and enlarged cup seen in the photographs of the optic nerve head (B) and with the visual field loss that is evident on standard automated perimetry (SAP) (C). Bottom: The left eye shows normal RNFL thickness on SD-OCT (A), normal appearance of the optic nerve head (B), and normal visual field (C).