Elsevier

Ophthalmology

Volume 117, Issue 12, December 2010, Pages 2337-2344
Ophthalmology

Original article
Retinal Nerve Fiber Layer Imaging with Spectral-Domain Optical Coherence Tomography: Pattern of RNFL Defects in Glaucoma

https://doi.org/10.1016/j.ophtha.2010.04.002Get rights and content

Objective

To characterize the distribution pattern, angular width, and area of retinal nerve fiber layer (RNFL) defects in glaucoma using spectral-domain optical coherence tomography (OCT).

Design

Prospective, cross-sectional study.

Participants

We included 113 normal subjects and 116 glaucoma patients.

Methods

One eye from each individual was randomly selected for Cirrus HD-OCT (Carl Zeiss Meditec Inc., Dublin, CA) RNFL imaging of the 6 × 6-mm2 parapapillary region. The RNFL defects were identified in the RNFL thickness deviation map as superpixels coded in red. The angular location and the angular width of RNFL defects were measured. The proportion of area with RNFL measurements within the normal ranges in the RNFL thickness deviation map was expressed as the RNFL area index (RAI): 1 – [area of superpixels coded in red/(6 × 6 – optic disc and parapapillary atrophic area)]. The diagnostic performance between RAI and average RNFL thickness was compared with the area under the receiver operating characteristic curve after adjusting refraction, signal strength, optic disc, and parapapillary atrophic areas.

Main Outcome Measures

Frequency distribution profiles and distribution patterns of RNFL defects, diagnostic sensitivity and specificity of RAI, and average RNFL thickness.

Results

The RNFL defects in glaucoma were most frequently found at the inferotemporal meridian at 284° (80.4%), followed by the superotemporal meridians at 73° (54.2%). The respective proportions of localized (angular width ≤30°) and diffuse (angular width >30°) RNFL defects were 11.4% and 70.5% in mild glaucoma (MD≥6 dB), and 4.2% and 94.5% in moderate to advanced glaucoma (MD<−6 dB). The RAI was 90.2±6.4% and 83.6±7.4% in the mild and moderate to advanced glaucoma groups, respectively. At a specificity of 90.0%, the respective diagnostic sensitivity of RAI and average RNFL thickness was 95.7% (95% confidence interval, 92.2–99.1%) and 94.0% (90.1–99.1%).

Conclusions

Analysis of the pattern of RNFL defects with spectral domain OCT imaging offers important insights in understanding the characteristics of RNFL damage. As RNFL defects expand in size as the disease progresses, measurement of the angular width and area of RNFL defects can provide an additional dimension for evaluation of glaucoma.

Financial Disclosure(s)

Proprietary or commercial disclosure may be found after the references.

Section snippets

Subjects

A total of 113 normal subjects and 116 glaucoma patients were consecutively enrolled. They were followed from September 2008 to July 2009 at the University Eye Center, the Chinese University of Hong Kong, and enrolled for the research study “RNFL Imaging with Spectral-Domain OCT,” which was designed to investigate the roles of RNFL imaging for detecting and following glaucoma. All subjects underwent a full ophthalmic examination, including measurement of visual acuity, refraction, intraocular

Results

Table 1 presents subject demographics. Among the 116 glaucoma patients, 44 had mild (MD≥−6 dB), 26 had moderate (−6 dB>MD>−12 dB), and 46 had advanced (MD≤−12 dB) visual field defects. There were significant differences in spherical refractive error, disc area, parapapillary atrophic area, and signal strength between the normal and glaucoma groups (all with P≤0.002). Glaucoma patients were more myopic and had larger optic disc and parapapillary atrophic areas.

Discussion

With detailed spatial analysis of the RNFL thickness deviation map constructed from the Cirrus HD-OCT, we characterized the distribution pattern, angular dimension and area of RNFL defects over a wide spectrum of glaucomatous damage. This information provides important insights to understanding the development and progression of RNFL damage in glaucoma.

In the frequency distribution analysis (Fig 2), 75% to 80% of glaucoma patients had RNFL loss evident at the inferotemporal meridians between

References (20)

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Manuscript no. 2009-1708.

Financial Disclosure(s): Christopher K.S. Leung – Speaker honorarium – Carl Zeiss Meditec, Heidelberg Engineering, Topcon; Research support – Carl Zeiss Meditec, Optovue

Robert N. Weinreb – Consultant – Carl Zeiss Meditec, Optovue, Topcon; Research support – Carl Zeiss Meditec, Heidelberg Engineering, Optovue, Topcon.

Supported by the Chinese University of Hong Kong Direct Grant.

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