Elsevier

Ophthalmology

Volume 121, Issue 7, July 2014, Pages 1341-1349
Ophthalmology

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

https://doi.org/10.1016/j.ophtha.2014.01.008Get rights and content

Objective

To investigate whether the rate of retinal nerve fiber layer (RNFL) thinning differs according to the microstructure of β-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 β-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 β-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 μm/year) than in the other groups (group B, −0.87±1.28 μm/year; group C, 0.20±1.86 μm/year; group D, −0.28±1.74 μm/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 β-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 β-zone PPA. It was faster for eyes with β-zone PPA with intact BM than for eyes without β-zone PPA or with β-zone PPA devoid of BM.

Section snippets

Methods

The participants in this study comprised patients from the Investigating Glaucoma Progression Study (IGPS), which is an ongoing prospective study on patients with glaucoma at the Seoul National University Bundang Hospital Glaucoma Clinic. They were consecutive patients who met the eligibility criteria and provided written informed consent to participate. This study was approved by the Seoul National University Bundang Hospital Institutional Review Board and followed the tenets of the

Baseline Characteristics

The study included 195 eyes of 195 patients with POAG who met the eligibility criteria, of whom 154 eyes had temporal β-zone PPA and were further classified into groups A (having PPA+BM only; n=64), B (having both PPA+BM and PPA–BM; n=58), and C (having PPA–BM only; n=32). The remaining 41 eyes did not have β-zone PPA and were categorized as group D (lacking β-zone PPA).

The interobserver agreement of determining the presence or absence of β-zone PPA on infrared fundus imaging was excellent

Discussion

Differences in the clinical characteristics between PPA types have been categorized according to the extent of the existing BM in the β-zone PPA area, and diverse mechanisms underlying the pathogenesis of PPA among POAG patients have been suggested. This study identified differences in the rate of RNFL thinning according to PPA type.

The findings of this study suggest that the risk of progressive RNFL thinning is greater in eyes having PPA with PPA+BM only (group A) than in eyes with other types

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    Supplemental material is available online at www.aaojournal.org.

    Financial Disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

    Funding: Supported by National Research Foundation of Korea Grant funded by Korean Government (800-20130242). The funding organization had no role in the design or conduct of this research.

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