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Moon, Jun, and Choi: Comparison of Retinal Nerve Fiber Layer Thickness in Early Normal-Tension Glaucoma and Early Primary Open-Angle Glaucoma
Original Article

J Korean Ophthalmol Soc 2010;51(2):248-253.

Published online: 7 September 2010

DOI: https://doi.org/10.3341/jkos.2010.51.2.248

Comparison of Retinal Nerve Fiber Layer Thickness in Early Normal-Tension Glaucoma and Early Primary Open-Angle Glaucoma

Sun-Kyung Moon, MD, Roo-Min Jun, MD, PhD, Kyu-Ryong Choi, MD, PhD

The Institute of Ophthalmology and Optometry, Department of Ophthalmology, Ewha Womans University School of Medicine, Seoul, Korea

Address reprint requests to Kyu-Ryong Choi, MD, PhD Department of Ophthalmology, Ewha Womans University School of Medicine, Mok-dong Hospital #911-1 Mok 5-dong Yangcheon-gu, Seoul 158-710, Korea Tel: 82-2-2650-5154, Fax: 82-2-2654-4334, E-mail: ckrey02@ewha.ac.kr

Received 29 April 2009       Accepted 4 November 2009

Copyright © 2010 Korean Ophthalmological Society

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Purpose

To investigate the comparison of retinal nerve fiber layer (RNFL) thickness parameters measured by optical coherence tomography (Stratus OCT 3000TM) and visual field indices in early normal-tension glaucoma (NTG) and early primary open-angle glaucoma (POAG).

Methods

Sixty-one early normal-tension glaucomatous eyes, 21 early primary open-angle glaucomatous eyes and 34 healthy control eyes were enrolled in this cross-sectional study. Each subject received a visual field test (Humphrey C30–2) and the fast RNFL thickness algorithm test by OCT. The correlations between RNFL thickness and visual field indices were analyzed. The sensitivity and specificity for the detection of early glaucoma were determined with the area under the receiver operating characteristics curve (AUROC).

Results

All RNFL thickness values except for the temporal quadrant RNFL thickness were significantly decreased in the early NTG and POAG groups (p<0.05). In early POAG, the average and superior quadrant RNFL thicknesses were significantly thinner than in the early NTG group. Significant correlations were observed between the PSD and the average and superior quadrant RNFL thicknesses in the early NTG and POAG groups (p<0.05). The average RNFL thickness for early glaucoma had the widest AUROC among all of the parameters.

Conclusions

In the early NTG group with visual field defects similar to those of early POAG, RNFL defects measured by OCT were less severe, particularly in the average and superior quadrant RNFLs.

Keywords: Normal-tension glaucoma, Optical coherence tomography, Primary open-angle glaucoma, Retinal nerve fiber layer thickness

References

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Figure 1.
ROC curve for OCT parameters.
jkos-51-248f1.tif
Table 1.
Clinical characteristics of the subjects (Mean± SD)
Normal Early NTG Early POAG p-value
No (eyes) 34 61 21
Male: Female 18:16 34:27 18:3
Age(years) 45.38±7.79 48.23±11.0 42.38±12.0 0.072
Refractive error (diopters) −0.94±1.76 −1.82±2.15 −2.79±3.28 0.056
IOP (mm Hg) 15.21±2.29 14.70±2.54 23.24±1.55†‡ 0.000
MD (dB) −0.57±0.69 −2.47±1.47* −2.49±1.46† 0.000
PSD (dB) 1.68±0.28 3.31±2.00* 3.77±2.82† 0.000

NTG=normal-tension glaucoma; POAG=primary open-angle glaucoma; p-value, by analysis of variances (ANOVA)

* p<0.05, normal vs. early NTG

† p<0.05, normal vs. early POAG

‡ p<0.05, early NTG vs. early POAG.

Table 2.
Comparison of the RNFL thickness (Mean± SD, μm)
Normal Early NTG Early POAG p-value
Superior quadrant 129.2±15.6 113.2±20.4* 99.2±24.9†‡ 0.000
Nasal quadrant 81.5±17.7 64.5±17.4* 60.0±11.5† 0.000
Inferior quadrant 136.8±16.2 116.5±23.1* 108.1±21.0† 0.000
Temporal quadrant 80.3±14.6 80.8±19.1 75.5±24.4 0.536
Average 107.0±8.3 93.8±13.7* 85.7±14.8†‡ 0.000
Twelve o'clock (superior) 130.8±22.7 113.0±24.2* 102.3±28.5† 0.000
One o'clock 128.3±21.5 108.8±31.5* 97.2±27.1† 0.000
Two o'clock 96.1±19.2 83.9±23.1* 81.0±28.5† 0.024
Three o'clock (nasal) 68.8±15.4 59.5±16.0* 63.0±21.1 0.041
Four o'clock 82.9±19.1 73.5±22.4* 71.5±27.0 0.096
Five o'clock 130.6±30.1 116.7±35.7* 111.9±34.7† 0.084
Six o'clock (inferior) 146.5±28.5 120.4±29.6* 116.1±27.3† 0.000
Seven o'clock 133.5±27.9 112.4±34.8* 96.1±36.2† 0.000
Eight o'clock 81.4±17.7 74.6±23.8 61.4±19.7†‡ 0.005
Nine o'clock (temporal) 64.8±14.7 59.8±15.5 55.7±11.5† 0.077
Ten o'clock 91.4±21.6 84.3±27.4 73.5±20.6† 0.036
Eleven o'clock 128.4±25.9 118.1±28.0 98.4±34.7†‡ 0.001

RNFL=retinal nerve fiber layer; NTG=normal-tension glaucoma; POAG=primary open-angle glaucoma; p-value, by analysis of variances (ANOVA)

* p<0.05, normal vs. early NTG

† p<0.05, normal vs. early POAG

‡ p<0.05, early NTG vs. early POAG.

Table 3.
Pearson's correlation between the RNFL thickness and MD, PSD in early NTG and early POAG
Early NTG
 Early POAG
MD PSD MD PSD
Superior quadrant 0.093 −0.291* 0.440 −0.660*
Nasal quadrant 0.185 −0.269* −0.263 0.016
Inferior quadrant 0.140 −0.195 0.328 −0.372
Temporal quadrant −0.001 −0.163 0.230 −0.382
Average 0.151 −0.333* 0.346 −0.566*

RNFL=retinal nerve fiber layer; NTG=normal-tension glaucoma; POAG=primary open-angle glaucoma; MD=mean deviation; PSD=pattern standard deviation

* p<0.05.

Table 4.
Diagnostic accuracy of OCT parameters to discriminate between early NTG and early POAG vs. normal
Normal vs. Early NTG AUROC (95% CI) Normal vs. Early POAG AUROC (95% CI)
Superior quadrant 0.724 (0.619–0.829) 0.824 (0.710–0.938)
Nasal quadrant 0.750 (0.653–0.856) 0.841 (0.737–0.945)
Inferior quadrant 0.755 (0.657–0.852) 0.852 (0.743–0.960)
Temporal quadrant 0.511 (0.394–0.628) 0.565 (0.397–0.733)
Average 0.806 (0.718–0.894) 0.896 (0.807–0.985)

OCT=optical coherence tomography; NTG=normal-tension glaucoma; POAG=primary open-angle glaucoma.

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