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

摘要

Objective: To investigate whether the rate of retinal nerve fiber layer (RNFL) thinning differs according to the microstructure of (3-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 beta-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 (3-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 mum/year) than in the other groups (group B, -0.87±1.28 mum/year; group C, 0.20±1.86 nm/year; group D, -0.28±1.74 mum/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 beta-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 beta-zone PPA or with beta-zone PPA devoid of BM.