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Joo, Choi, Kim, and Kang: Comparison between Optic Disc Torsion of Fellow Eyes in Unilateral Normal-tension Glaucoma and Normal Eyes
Original Article

Journal of the Korean Ophthalmological Society 2017; 58(8): 974-980.

Published online: 16 August 2017

DOI: https://doi.org/10.3341/jkos.2017.58.8.974

Comparison between Optic Disc Torsion of Fellow Eyes in Unilateral Normal-tension Glaucoma and Normal Eyes

Jin-Ho Joo, MD1, Jeong Han Choi, MD2, Tae Gi Kim, MD1, Jaheon Kang, MD, PhD1

1Department of Ophthalmology, Kyung Hee University Hospital at Gangdong, Kyung Hee University School of Medicine, Seoul, Korea.

2Division of Ophthalmology, Department of Medicine, Kyung Hee University Graduate School, Seoul, Korea.

Address reprint requests to Jaheon Kang, MD, PhD. Department of Ophthalmology, Kyung Hee University Hospital at Gangdong, #892 Dongnam-ro, Gangdong-gu, Seoul 05278, Korea. Tel: 82-2-440-7751, Fax: 82-2-440-7756, Kjh0614@khu.ac.kr

Received 26 May 2017       Revised 27 June 2017       Accepted 2 August 2017

©2017 The Korean Ophthalmological Society

(open-access):

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 determine the association between optic disc tilt and torsion of glaucomatous and fellow eyes of unilateral normal-tension glaucoma (NTG) patients and normal.

Methods

We measured optic disc tilt and torsion of 23 unilateral NTG patients and 23 normal controls by analyzing fundus photography and compared 3 groups. We also measured retinal nerve fiber layer (RNFL) thickness through optical coherence tomography in 23 unilateral NTG patients and compared the findings with those of normal eyes.

Results

The mean values of optic disc tilt ratio and torsion degree in glaucomatous eyes were 1.17 ± 0.19° and 15.57 ± 8.16°, respectively, while those in fellow eyes were 1.10 ± 0.10° and 8.26 ± 5.20°. There was no significant difference in tilt ratio (p = 0.109), but there was a significant difference in torsion degree (p = 0.001). The mean values of optic disc tilt ratio and optic disc torsion in the controls were 1.11 ± 0.07° and 3.25 ± 2.69°, respectively. Also, there was no significant difference in optic disc tilt ratio (p = 0.601), but a significant difference in optic disc torsion between fellow eyes and controls (p < 0.001). The RNFL thickness of the same torsion direction in unilateral NTG eyes was measured to be 49.35 ± 17.18 µm smaller than the normal value (mean RNFL thickness: 71.91 ± 16.92 µm). Reduced RNFL thickness of the same torsion direction between glaucomatous eyes and fellow eyes was significantly different (p < 0.001). In addition, it was confirmed that RNFL thickness was significantly decreased according to the degree of disc torsion (p = 0.024).

Conclusions

The optic disc torsion showed a significant difference between glaucomatous and fellow eyes in unilateral NTG patients and normal controls. Also, the RNFL thickness significantly decreased according to the degree of the optic disc torsion. Therefore, fellow eyes of unilateral NTG patients need to be carefully monitored for the progression of glaucoma.

Keywords: Optic disc torsion, Retinal nerve fiber layer, Unilateral normal tension glaucoma

Figures and Tables

Figure 1

Definitions of optic disc tilt and torsion degree with Image J software. Optic disc tilt ratio was defined as the ratio between the longest diameter (LD) and shortest diameter (SD) of the optic disc. Optic disc torsion degree was measured between the LD and vertical meridian (VM) of the optic disc (θ).

jkos-58-974-g001
Figure 2

The bar chart of the optic disc tilt ratio and torsion degree. Comparisons of the optic disc tilt ratio (A) and torsion degree (B) between glaucomatous eyes and fellow eyes of 23 patients with unilateral normal-tension glaucoma (NTG) patients, and 46 normal controls. G-NTG = glaucomatous eyes of unilateral normal-tension glaucoma; Fellow eye-NTG = contralateral normal eyes of unilateral normal-tension glaucoma.

jkos-58-974-g002
Figure 3

Scatter map between optic disc torsion and retinal nerve fiber layer (RNFL) thickness of the same direction. Scatterplots showing the relationship between the optic disc torsion degree and the same directional RNFL thickness (A) and the difference between the same directional RNFL thickness and normal values (B). Pearson correlation coefficient R values are shown. S_RNFL = same directional RNFL thickness (µm); S_RNFL_D = difference between the same directional RNFL thickness and normal values (µm).

jkos-58-974-g003
Table 1

The results of eye examinations and demographics in 23 patients with unilateral normal-tension glaucoma (NTG) and 46 eyes of 23 normal controls

jkos-58-974-i001

Values are presented as mean ± SD unless otherwise indicated.

IOP = intraocular pressure; SE = spherical equivalent.

Table 2

The optic disc tilt ratio and torsion degree of 23 patients with unilateral normal-tension glaucoma (NTG) and 46 eyes of 23 normal controls

jkos-58-974-i002

Values are presented as mean ± SD unless otherwise indicated.

Table 3

Comparison of Retinal nerve fiber layer (RNFL) thickness by spectral-domain optical coherence tomography (OCT) between glaucomatous eyes and contralateral normal eyes of 23 patients with unilateral normal-tension glaucoma (NTG)

jkos-58-974-i003

Values are presented as mean ± SD unless otherwise indicated.

*Paired t-test; †p < 0.05.

Notes

Conflicts of Interest The authors have no conflicts to disclose.

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