J Korean Ophthalmol Soc.  2017 Aug;58(8):974-980. 10.3341/jkos.2017.58.8.974.

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

Affiliations
  • 1Department of Ophthalmology, Kyung Hee University Hospital at Gangdong, Kyung Hee University School of Medicine, Seoul, Korea. Kjh0614@khu.ac.kr
  • 2Division of Ophthalmology, Department of Medicine, Kyung Hee University Graduate School, Seoul, Korea.

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.

Keyword

Optic disc torsion; Retinal nerve fiber layer; Unilateral normal tension glaucoma

MeSH Terms

Glaucoma*
Humans
Nerve Fibers
Photography
Reference Values
Retinaldehyde
Tomography, Optical Coherence
Retinaldehyde

Figure

  • 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).

  • 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.

  • 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).


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