Topographic Relationship with a Retinal Nerve Fiber Layer Defect Differs between β-Zone and γ-Zone Parapapillary Atrophy

Figure 1

Measurement of the angular location of the point of maximum radial extent of parapapillary atrophy (PMRE) and a localized retinal nerve fiber layer (RNFL) defect and the angular extent of the localized RNFL defect. The PMRE and the RNFL defects were evaluated in a stereo disc photograph (a) and a red-free fundus photograph (b). The PMRE was the point on the parapapillary atrophy (PPA) margin at which the radial extent of PPA was maximal. The angular location of the PMRE was determined by measuring the angle between a reference line connecting the fovea and the disc center (line R [7, 13] and a line from the center of the disc to the PMRE (angle α)). Points S and E are the start and end points of the RNFL defect, respectively. The angular extent was defined as the circumferential angle between points S and E. The angular location was defined as the angle between line R and a line drawn from the center of the disc to the midpoint of the RNFL defect (angle β).

(a)

(b)