Purpose
It has long been recognized that beta-zone parapapillary atrophy (PPA) is topographically correlated with retinal nerve fiber layer defect. Recently, beta-zone PPA has been further divided into beta-zone and gamma-zone. This study was conducted to investigate whether the topographic correlation with retinal nerve fiber layer (RNFL) defect differs between beta-zone and gamma-zone PPA.
Methods
Color and red-free fundus photographs of primary open angle glaucoma (POAG) patients who had beta-zone or gamma-zone PPA, and a single localized RNFL defect were reviewed. The PPA was classified according to the presence or absence of the Bruch’s membrane on the PPA bed in the spectral domain optical coherence tomography image. Angular location of the RNFL defect and the point of maximum radial extent (PMRE) of PPA were measured with the fovea-disc axis set at 0 degree. Angular extent of RNFL defect and PPA were also measured.
Results
Of 464 eyes, 122 (26.3%) POAG eyes had single localized RNFL defect together with beta-zone (group A, n=53) or gamma-zone PPA (group B, n=27). There was no significant difference in the angular location of PMRE (P = 0.917) and extent of RNFL defect (P = 0.146) between the 2 groups. However, the angular distance between the RNFL defect and PMRE was significantly greater in group B than in group A ( 36.51 ± 21.13° vs 66.96 ± 24.13°, P<0.001).
Conclusions
The RNFL defect was observed close to the PMRE in eyes with beta-zone PPA, but not in eyes with gamma-zone PPA. This finding supports that the beta-zone and gamma-zone PPA have different pathogenic influence regarding glaucomatous optic nerve damage.