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Ahn and Chang: Optic Cup Slope as a Numeric Representative of Glaucomatous Cupping
Original Article

J Korean Ophthalmol Soc 2007;54(3):462-468.

Published online: 24 August 2007

DOI: https://doi.org/10.3341/jkos.2013.54.3.462

Optic Cup Slope as a Numeric Representative of Glaucomatous Cupping

Sang Il Ahn, MD, Jee Ho Chang, MD, PhD

Department of Ophthalmology, Soonchunhyang University College of Medicine, Bucheon, Korea

Address reprint requests to Jee Ho Chang, MD, PhD Department of Ophthalmology, Soonchunhyang University Bucheon Hospital #170 Jomaru-ro, Wonmi-gu, Bucheon 420-767, Korea Tel: 82-32-621-5426, Fax: 82-32-621-5435, E-mail: jhchang@schmc.ac.kr

Received 20 April 201226 June 2012       Accepted 7 January 2013

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

To objectively define the degree of cupping, the authors extracted 3-dimensional slope surface maps from Cirrus HDTM-OCT data and assessed their differentiating characteristics between normal subjects and glaucomatous patients. Methods: One eye from each of 40 normal subjects and 1 eye from each of 39 patients with glaucoma were examined using automated visual field perimetry and Cirrus HDTM-OCT. The Optic Disc Cube 200 × 200 protocol was performed. The individual OCT data were reconstructed as the 3-dimensional surface maps of the optic disc cup and the slope of each contour was calculated using custom-developed software. Several disc cup slope parameters were derived. The parameters measuring the internal features of the optic disc cup were calculated and compared between groups.

Results

Sum of cup slope, sum of thresholded cup slope, and sum of thresholded cup slope / thresholded cup area parameters were differentiating factors between the normal and glaucoma groups (p < 0.05). The area under the receiver operating characteristic curve (AUROC) value of the slope parameters ranged from 0.718 to 0.753. The sum of thresholded cup slope / thresholded cup area parameter was well correlated with visual field mean deviation (r = -0.250, p = 0.028). Conclusions: The optic disc cup slope parameter obtained with OCT may be a useful parameter for representing glaucomatous cupping.

Keywords: Cup slope, Disc cup, Glaucoma, OCT

References

1. RR Allingham, KF Damji, S Freedman. Shields' textbook of glaucoma. 5th ed.Lippincott Willliams & Wilkins;2005. chap. 5.
2. Hayreh SS. Pathogenesis of cupping of the optic disc. Br J Ophthalmol. 1974; 58:863–76.
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3. Quigley HA, Addicks EM, Green WR, Maumenee AE. Optic nerve damage in human glaucoma. II. The site of injury and susceptibility to damage. Arch Ophthalmol. 1981; 99:635–49.
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4. Quigley HA, Green WR. The histology of human glaucoma cupping and optic nerve damage: clinicopathologic correlation in 21 eyes. Ophthalmology. 1979; 86:1803–30.
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5. Miglior S, Casula M, Guareschi M, et al. Clinical ability of Heidelberg retinal tomograph examination to detect glaucomatous visual field changes. Ophthalmology. 2001; 108:1621–7.
6. Schuman JS, Wollstein G, Farra T, et al. Comparison of optic nerve head measurements obtained by optical coherence tomography and confocal scanning laser ophthalmoscopy. Am J Ophthalmol. 2003; 135:504–12.
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7. Dong J, Chihara E. Slope analysis of the optic disc in eyes with ocular hypertension and early normal tension glaucoma by confocal scanning laser ophthalmoscope. Br J Ophthalmol. 2001; 85:56–62.
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8. Cullinane AB, Waldock A, Diamond JP, Sparrow JM. Optic disc cup slope and visual field indices in normal, ocular hypertensive and early glaucomatous eyes. Br J Ophthalmol. 2002; 86:555–9.
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Figure 1.
3D reconstruction of the optic disc cup. (A) Representative horizontal Cirrus HDTM -OCT image of the optic disc cup. (B) 3D surface map image reconstructed by custom develped software.
jkos-54-462f1.tif
Figure 2.
Calculation of slope for one voxel. (A) 3D surface map of disc cup. (B) Schematic drawing of disc cup. (C) 4 Slope of one voxel obtained by disc cup analysis program: horizontal, vertical and 2 diagonal.
jkos-54-462f2.tif
Figure 3.
Comparison between glaucomatous cupping and physiologic large cup. (A) Representative glaucomatous cupping. (B) Representative physiologic large cup. Left graph is the horizontal Cirrus HDTM -OCT image of the optic disc cup. M iddle and right graph is the print out of the results obtained by the disc cup analysis program. M iddle graph shows original slope data and right shows graph after removal of under the threshold slope data. The sum of cup slope parameter of physiologic the large cup was more larger than the glaucomatous cupping (12204 vs 11103) but the sum of thresholded cup slope parameter of physiologic large cup was smaller than the physiologic large cup (1926 vs 3526).
jkos-54-462f3.tif
Figure 4.
Reciever operating characteristic curves for the best seperating parameters between normal and glaucoma groups.
jkos-54-462f4.tif
Table 1.
Dermographic data of study participants
Normal (n = 40) Glaucoma (n = 39) p
Age (year) 49.7 ± 9.6 52.3 ± 11.9 0.325
Sex (%, male) 68 59 0.456
SE (D) -2.07 ± 2.51 -1.69 ± 1.94 0.483
IOP (mm Hg) 15.4 ± 3.2 19.7 ± 5.1 <0.001*
MD 0.01 ± 1.24 -1.80 ± 1.36 <0.001*
PSD 1.85 ± 0.53 3.21 ± 1.70 <0.001*
C/D ratio 0.33 ± 0.05 0.66 ± 0.17 <0.001*
Average RNFL thickness (μm) 98.7 ± 6.9 75.4 ± 7.5 <0.001*

Values are presented as mean ± SD.

SE = spherical equivalent; IOP = intraocular pressure; C/D = Cup/disc; RNFL = retinal nerve fiber layer.

* p < 0.05.

Table 2.
Disc cup parameters, as determined by Cirrus HDTM-OCT
Normal (n = 40) Glaucoma (n = 39) p
Cup volume 19487 ± 15996 47403 ± 30345 <0.001*
Cup area 937.8 ± 440.5 1794.1 ± 729.4 <0.001*
Thresholded cup area 231.8 ± 174.5 348.4 ± 182.3 0.005*
Sum of cup slope 7463.9 ± 4696.6 13207.3 ± 6012.4 <0.001*
Sum of cup slope / cup area 7.62 ± 2.28 7.41 ± 1.65 0.691*
Sum of thresholded cup slope 1872.1 ± 2108.3 3761.6 ± 2493.1 0.002*
Sum of thresholded cup slope / thresholded cup area 7.96 ± 2.79 10.19 ± 2.86 <0.001*

Values are presented as mean ± SD.

* p < 0.05.

Table 3.
Area under the ROC curve, sensitivity, specificity and cut-off value by each parameters
AUROC Sensitivity Specificity Cut-off value p
Average RNFL thickness 0.991 97% 98% 89.5 <0.001*
Cup volume 0.761 72% 70% 27640 <0.001*
Cup area 0.794 71% 72% 1369.5 <0.001*
Thresholded cup area 0.703 67% 62% 231.0 0.002*
Sum of cup slope 0.740 72% 70% 9779 <0.001*
Sum of cup slope / cup area 0.503 48% 44% 7.04 0.964*
Sum of thresholded cup slope 0.753 74% 70% 2002 <0.001*
Sum of thresholded cup slope / thresholded cup area 0.718 69% 67% 8.83 0.001*

RNFL = retinal nerve fiber layer, AUROC = area under the receiver operating characteristic curve.

* p < 0.05.

Table 4.
Correlation between Hemphrey visual field indices and disc cup parameters
MD
Correlation coefficient p
Cup volume -0.229 0.055
Cup area -0.192 0.095
Thresholded cup area -0.168 0.144
Sum of cup slope -0.188 0.101
Sum of cup slope / cup area -0.024 0.835
Sum of thresholded cup slope -0.223 0.051
Sum of thresholded cup slope / thresholded cup area -0.250 0.028*

* p < 0.05.

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