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Kim and Choi: GDx-VCC Performance to Discriminate Normal, Pre-perimetric Glaucomatous Eyes
Original Article

J Korean Ophthalmol Soc 2007;48(12):1686-1693.

Published online: 30 August 2007

DOI: https://doi.org/10.3341/jkos.2007.48.12.1686

GDx-VCC Performance to Discriminate Normal, Pre-perimetric Glaucomatous Eyes

Hyun-Jin Kim, M.D., Kyu-Ryong Choi, M.D.

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

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

Received 31 January 2007       Accepted 31 July 2007

Copyright © 2007 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

This study was designed to assess the diagnostic value of scanning laser polarimetry with variable comeal compensation (GDx-VCC) in the diagnosis of preperimetric glaucoma.

Methods

The study included 132 eyes of 132 patients with normal intraocular pressure, including 38 normal eyes, 60 eyes with pre-perimetric glaucoma, and 34 eyes with early glaucoma. The parameters of GDx-VCC were analyzed and compared in these groups using ANOVA. The parameter with the most powerful diagnostic value was defermirred by an ROC curve, and it's sensitivity and specificity were calculated.

Results

Among GDx-VCC parameters, NFI was the most valuable parameter that could detect pre-perimetric glaucoma in normal eyes. A cut-off value of 12 was the optimal NFI value, which offered the highest sensitivity and specificity in discriminating between normal and pre-perimetric glaucomatous eyes. However, there were no statistically significant differences in GDx-VCC parameters between pre-perimetric and early glaucomatous eyes. A statistically significant correlation was found between NFI and visual field indices in early glaucomatous eyes.

Conclusions

GDx-VCC can be useful as a screening test for early detection of pre-perimetric and early glaucoma with normal intraocular pressure.

Keywords: GDx-VCC, Pre-perimetric glaucoma, Scanning laser polarimetry

References

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Figure 1.
ROC curves for NFI for discrimination.
jkos-48-1686f1.tif
Table 1.
Characteristics and MD*, PSD† in each group
  Normal Pre-perimetric glaucoma Early glaucoma p-value
No. of eyes 38 60 34
Age (years) 41.58± 12.91 47.03±8.65 51.35±11.05 <0.05
Gender (M:F) 18:20 32:28 12:22
IOP (mmHg) 16.21±2.80 16.26±2.75 16.76±3.04 >0.05
Refractive error (D) -1.32±1.26 -0.87±1.32 -1.05±1.71 >0.05
CD ratio 0.42±0.10 0.69±0.08 0.70±0.08 <0.05
MD (dB) -0.24±0.86 -0.93±1.60 -2.14±1.66 <0.05
PSD (dB) 1.57±0.23 1.87±0.35 3.42±2.13 <0.05

MD* mean deviation,

PSD† pattern standard deviation.

Table 2.
Mean values of GDx-VCC parameters in each groups (Mean±SD)
  Normal Pre-perimetric glaucoma Early glaucoma p-value* p-value† p-value‡
NFI 13.68±6.03 19.96±9.79 22.59±7.14 <0.05 <0.05 >0.05
TSNIT average 57.42±3.52 55.89±8.14 54.12±4.74 >0.05 <0.05 >0.05
Superior average 73.15±3.90 67.96±5.56 67.08±7.02 <0.05 <0.05 >0.05
Inferior average 67.51±6.55 63.87±7.54 63.75±12.33 >0.05 >0.05 >0.05
TSNIT SD 25.36±2.90 22.94±3.75 21.42±6.73 >0.05 <0.05 >0.05
Superior ratio 7.22±14.78 3.23±0.86 2.94±0.14 >0.05 >0.05 >0.05
Inferior ratio 3.73±0.95 3.23±0.85 2.81± 1.09 <0.05 <0.05 >0.05
Maximum modulation 3.22±0.97 2.70±0.77 2.45±0.82 <0.05 <0.05 >0.05
Superior maximum 86.88±6.97 81.09±11.22 80.23±9.12 <0.05 <0.05 >0.05
Inferior maximum 83.01±8.37 80.21±9.09 78.49±13.18 >0.05 >0.05 >0.05
Ellipse modulation 4.34±1.20 4.00± 1.12 3.61± 1.15 >0.05 <0.05 >0.05

* Between normal and pre-perimetric glaucoma.

† Between normal and early glaucoma.

‡ Between pre-perimetric glaucoma and early glaucoma.

Table 3.
Pearson correlation coefficient between NFI and visual field indices in early glaucomatous eyes
  MD P† PSD P‡
NFI -0.419 <0.01 0.421 <0.01
TSNIT SD 0.365 <0.05 -0.379 <0.01
Max modulation 0.476 <0.01 -0.336 <0.05
Ellipse modulation 0.397 <0.01 -0.462 <0.01

† p value in MD,

‡ p value in PSD.

Table 4.
Area under ROC curves for discrimination
Parameters AUROC
normal and preperimetric glaucoma preperimatric and early glaucoma normal and early glaucoma
NFI 0.755 0.675 0.889
TSNIT average 0.277 0.509 0.282
Superior average 0.202 0.471 0.196
Inferior average 0.379 0.415 0.322
TSNIT SD 0.283 0.403 0.239
Superior ratio 0.307 0.318 0.229
Inferior ratio 0.331 0.293 0.227
Max modulation 0.337 0.302 0.220
Superior maximum 0.258 0.458 0.256
Inferior maximum 0.346 0.389 0.287
Ellipse modulation 0.402 0.320 0.290
Table 5.
Likelihood ratios for NFI at three different cutoff values to discriminating normal and pre-perimetric and early glaucomatous eyes
  Between normal and pre-perimetric g laucoma Between pre-perimetric glaucoma and early glaucoma
Criterion +LR -LR +PV -PV +LR -LR +PV -PV
>10 1.27 0.25 66.7 71.4 1.07 0.00 37.0 100.0
>12* 1.71 0.21 73.0 75.0 1.05 0.59 37.2 75.0
>14 1.90 0.48 0.48 57.1 1.26 1.26 41.7 81.8
>16 2.53 0.59 0.59 51.7 1.54 1.54 46.7 82.4
>17† 2.06 0.72 0.72 46.9 1.90 1.90 51.9 85.0
>18 2.74 0.67 0.67 48.5 1.49 1.49 45.8 73.9
>19 2.32 0.75 0.75 45.7 1.76 1.76 50.0 76.0
>21 5.70 0.74 0.74 46.2 1.96 1.96 52.6 75.0
>22 5.07 0.77 0.77 45.0 1.76 1.76 50.0 6.6

+LR positive likelihood ratio, -LR negative likelihood ratio.

+PV positive predictive value, -PV negative predictive value.

* cut-off value between normal and pre-perimetric glaucoma.

† cut-off value between pre-perimetric glaucoma and early glaucoma.

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