Microstructure of β-Zone Parapapillary Atrophy and Rate of Retinal Nerve Fiber Layer Thinning in Primary Open-Angle Glaucoma

Objective: To investigate whether the rate of retinal nerve fiber layer (RNFL) thinning differs according to the microstructure of beta-zone parapapillary atrophy (PPA) as evaluated by spectral-domain (SD) optical coherence tomography (OCT) in primary open-angle glaucoma (POAG). Design: Prospective, observational, comparative study. Participants: A total of 195 eyes with POAG that had been evaluated by serial SD-OCT RNFL thickness measurements for >= 2 years. Methods: On the basis of the extent of Bruch's membrane (BM) within the b-zone PPA (area without retinal pigment epithelium [RPE]), as shown in the infrared fundus images, PPA was divided into PPA(+BM) (PPA with intact BM) and PPA(-BM) (PPA devoid of BM). Eyes were categorized into group A (having PPA(+BM) only, n=64), group B (having both PPA(+BM) and PPA(-BM), n=58), group C (having PPA(-BM) only, n=32), and group D (without beta-zone PPA, n=41). The rate of progressive OCT RNFL thinning was determined by linear regression and compared between groups. Factors influencing the rate of RNFL thinning were evaluated, including age, sex, follow-up duration, history of filtering surgery, baseline RNFL thickness, baseline intraocular pressure (IOP), mean IOP and IOP fluctuation during follow-up, PPA types, baseline PPA width, PPA width increase, axial length (AXL), central corneal thickness, and visual field mean deviation (MD). Main Outcome Measures: Rate of thinning of OCT RNFL thicknesses over time. Results: Patients in groups B and C were significantly younger and more myopic, and had a greater AXL, than those in groups A and D (all P < 0.001). The rate of global RNFL thinning was significantly faster in group A (1.66 +/- 2.94 mu m/year) than in the other groups (group B, 0.87 +/- 1.28 mu m/year; group C, 0.20 +/- 1.86 mu m/year; group D, -0.28 +/- 1.74 mu m/year; P = 0.001). Multivariate regression showed a significant association of shorter follow-up period (P = 0.016), greater baseline global RNFL thickness (P = 0.035), type of b-zone PPA (group A, P = 0.023), and greater baseline PPA(+BM) width (P = 0.034) with a faster rate of RNFL thinning. Conclusions: The rate of RNFL thinning differed according to the microstructure of beta-zone PPA. It was faster for eyes with beta-zone PPA with intact BM than for eyes without b-zone PPA or with beta-zone PPA devoid of BM. (C) 2014 by the American Academy of Ophthalmology.