Spectral-domain optical coherence tomography detects optic atrophy due to optic tract syndrome

  • Akiyasu Kanamori
  • Makoto Nakamura
  • Yuko Yamada
  • Akira Negi
Neurophthalmology

DOI: 10.1007/s00417-012-2096-3

Cite this article as:
Kanamori, A., Nakamura, M., Yamada, Y. et al. Graefes Arch Clin Exp Ophthalmol (2013) 251: 591. doi:10.1007/s00417-012-2096-3

Abstract

Background

Unilateral injury of the optic tract leads to asymmetrical optic atrophy in both eyes derived from the crossing of the nerve fibers at the chiasm. This report demonstrates unique imaging appearances of optic atrophy due to this uncommon condition detected by spectral-domain optical coherence tomography (SD-OCT).

Methods

Cirrus and RTVue measurements were performed in four cases of optic tract syndrome. Circumpapillary retinal nerve fiber layer (cpRNFL) thickness was obtained from both instruments and ganglion cell complex (GCC) integrity was obtained from RTVue. The presumable reduction rates of quadrant cpRNFL thickness were calculated from the published normative database and compared between eyes with temporal hemianopia and those with nasal hemianopia.

Results

Both devices showed significant reduction of cpRNFL thickness, but did not have statistical difference in the reduction rates at temporal or nasal quadrant cpRNFL between contralateral and ipsilateral eyes to the lesion. Color-coded maps helped to visualize the unique pattern of cpRNFL and GCC thinning.

Conclusions

SD-OCT can be used as a diagnostic tool for the optic tract syndrome.

Keywords

Optic tract syndrome Spectral-domain optical coherence tomography Retinal nerve fiber layer Ganglion cell complex 

Introduction

In optic tract syndrome (OTS), injury of the unilateral optic tract causes incongruous homonymous hemianopia, a relative afferent pupillary defect (RAPD) in the contralateral eye, and characteristic optic atrophy in both eyes [1]. RAPD is due to the fact that there are more crossed than uncrossed fibers at the chiasm, with the proportion of decussating and non-decussating fibers estimated to be 53:47 %. The uncrossed, temporal projection of the nerve fiber is affected in the eye ipsilateral to the damaged optic tract, resulting in preferential atrophy of the superior and inferior parts of the optic disc rim. In contrast, the crossed, nasal projection of the nerve fibers is damaged by the lesion in the contralateral eye, leading to the preferential atrophy of temporal and nasal parts of the optic disc rim, which is denoted as band atrophy. Previously, we and other investigators have demonstrated characteristic thinning of the circumpapillary retinal nerve fiber layer (cpRNFL) due to OTS detected by time-domain optical coherence tomography (TD-OCT) [2, 3]. TD-OCT also detected cpRNFL loss in eyes with band atrophy [4]. The recent introduction of spectral-domain OCT (SD-OCT) has enhanced scan resolution, provides more reproducible images and allows us to evaluate inner retinal layer architecture in the macula as ganglion cell complex (GCC) integrity [5]. Here, we report that SD-OCT instruments can be used to clearly visualize the unique pattern of cpRNFL and GCC atrophy characteristic of OTS.

Materials and methods

Four patients with OTS were recruited from Kobe University Hospital (Kobe, Japan) for this observational study. Three patients (#1-3) had right-sided hemianopia with an RAPD in their right eyes due to lesions in the left optic tract, whereas one patient (#4) had left-sided hemianopia with an RAPD in her left eye. Visual fields of the four patients were shown in Fig. 1. The mean age was 25.3 years old. Table 1 summarizes patient demographics.
Fig. 1

Visual fields as determined by Goldmann perimetry in four cases. Cases #1-3 had left hemianopia, and case #4 had right hemianopia

Table 1

OTS patient demographics and data from observational study of cnRNFL and GCC atrophy  

     

RNFL measurements

RTVue

Case

Gender

Age

Diagnosis of affected optic

Side

Temporal

Superior

Nasal

Inferior

Temporal

Superior

Nasal

Inferior

1

Male

20

glioma

Left

Right eye

52

85

51

88

52

94

50

104

Left eye

48

57

49

72

55

81

43

78

2

Male

28

cancer metastasis

Left

Right eye

67

96

65

104

72

95

40

102

Left eye

64

97

42

65

65

91

52

71

3

Female

22

enous malfo

Left

Right eye

44

89

53

114

54

92

42

122

Left eye

48

87

67

66

55

90

78

81

4

Female

31

brain trauma

Right

Right eye

45

86

58

64

57

100

70

85

Left eye

46

104

52

95

33

103

44

113

Two SD-OCT measurements were performed on the same day within 3 years from the notice of visual field loss. In RTVue-100 OCT (version 4.0.5.39, Optovue Inc.), the optic nerve head map protocol was applied to evaluate the cpRNFL. The GCC protocol was used to evaluate the GCC. Cirrus OCT (version 5.1.0.96, Carl Zeiss Meditec Inc.) used the optic disc cube protocol to determine cpRNFL thickness. Presumed rates of reduction in quadrant cpRNFL thickness in eyes with optic tract syndrome were calculated by extrapolating cpRNFL thickness in normal eyes at the age of 25.3 years from regression analyses based on the normal database from our recently published study [6]. The adjusted temporal, superior, nasal and inferior cpRNFL thickness by RTVue in normal eyes at 25.3 years old were 79.2, 120, 71.5 and 127.1 μm, respectively. These parameters by Cirrus were 70, 110.9, 65.8 and 114.8 μm, respectively.

Results

Figure 2 and Table 1 show cpRNFL thickness as measured by RTVue and Cirrus. In the contralateral eyes (the right eyes in case #1-3 and the left eye in case #4), the temporal and nasal (horizontal) cpRNFL values were reduced. In contrast, the superior and inferior (vertical) cpRNFL were preferentially reduced compared to the horizontal cpRNFL in the ipsilateral eyes (the left eyes in case #1-3 and the right eye in case #4). This trend was clearly visible in the color-coded map of the area around the optic nerve head, as depicted by RTVue analysis, which revealed a deviation of the two-dimensional RNFL thickness distributions adjacent to the optic disc. The horizontal RNFL thickness in the contralateral eyes appeared black in color, whereas the temporal-superior and temporal-inferior RNFL in the ipsilateral eyes appeared red and yellow. The mean ± standard error of the mean (SEM) for the presumed rates of reduction in the temporal, superior, nasal and inferior cpRNFL quadrants as determined by RTVue analysis was 33 ± 10, 20 ± 2.0, 38 ± 3.0, and 13 ± 3.7 % in the contralateral eye and 27 ± 2.9, 25 ± 3.2, 15 ± 11.2 and 38 ± 2.3 % in the ipsilateral eye, respectively. For the Cirrus measurements, the RNFL deviation map and TSNIT profiles detected the reduction in the thickness of the cpRNFL. The deviation map, which was based on data from a built-in normative control database, revealed horizontal cpRNFL thinning in the contralateral eyes and vertical RNFL thinning in the ipsilateral eyes, especially in case #3. In the RNFL TSNIT profiles, a so-called “double hump pattern”, which represents thicker RNFL in the superior and inferior quadrants and thinner RNFL in the temporal and nasal quadrants, was preserved in the contralateral eyes but lost in the ipsilateral eyes. The mean ± SEM of the presumed rates of thickness reduction in the temporal, superior, nasal and inferior RNFL quadrants as detected by Cirrus was 25 ± 7.4, 16 ± 3.7, 18 ± 4.5 and 13 ± 4.9 % in the contralateral eye and 27 ± 6.1, 26 ± 7.7, 18 ± 8.2 and 42 ± 1.6 % in the ipsilateral eye, respectively. Among four quadrants examined with regard to cpRNFL thickness, only the inferior quadrant exhibited a significant difference in the rate of reduction in RNFL thickness when contralateral and ipsilateral eyes were compared (Cirrus, p = 0.016; RTVue, p = 0.018; paired t-test).
Fig. 2

The cpRNFL measurements as evaluated by RTVue and Cirrus are shown. The colored map of the area around the optic nerve head provided by the RTVue indicates thick and thin regions of the RNFL in red and black, respectively. The thickness of the horizontal RNFL was decreased in the right eyes of cases #1 through 3 and the left eye of case #4 (the eyes contralateral to the damaged optic tract). In contrast, temporal superior and inferior areas of the cpRNFL displayed wedge-shaped regions of reduced thickness in the left eyes of cases #1 through 3 and the right eye of case #4 (eyes ipsilateral to the damaged optic tract). In the deviation map of Cirrus measurements, any areas of the cpRNFL below the 99 % and 95 % ranges in terms of thickness are indicated in red and yellow, respectively. Horizontal cpRNFL was decreased in the contralateral eyes, but vertical cpRNFL loss was detected in the ipsilateral eyes. The TSNIT profile curves demonstrated a double-hump pattern in the contralateral eyes but not in the ipsilateral eyes

Table 1

Patient demographics and quadrant cpRNFLthickness measured by SD-OCT

cpRNFLthickness

   

Side of affected optic tract

  

Visual acuity

Cirrus

RTVue

Gender

Age

Diagnosis

Durationa

Side

Temporal

Superior

Nasal

Inferior

Temporal

Superior

Nasal

Inferior

Male

20

glioma

Left

3 months

Right eye

20/20

52

85

51

88

52

94

50

104

     

Left eye

20/20

48

57

49

72

55

81

43

78

Male

28

cancer metastasis

Left

1 months

Right eye

20/20

67

96

65

104

72

95

40

102

     

Left eye

20/20

64

97

42

65

65

91

52

71

Female

22

arteriovenous malformation

Left

4 months

Right eye

20/20

44

89

53

114

54

92

42

122

     

Left eye

20/20

48

87

67

66

55

90

78

81

Female

31

brain trauma

Right

3 years

Right eye

20/20

45

86

58

64

57

100

70

85

     

Left eye

20/20

46

104

52

95

33

103

44

113

cpRNFL, circumpapillary retinal nerve fiber layer

aDuration, OCT measurements and the notice of visual field loss

The GCC as evaluated using RTVue analysis is shown in Fig. 3. All cases showed characteristic patterns of GCC thinning in both eyes, which is compatible with OTS. The contralateral eyes showed an apparent GCC reduction in the area nasal to the fovea, whereas the ipsilateral eyes exhibited a significant GCC reduction in the area temporal to the fovea.
Fig. 3

GCC as measured by RTVue. Any areas of the cpRNFL below the 99 % and 95 % ranges in terms of thickness are indicated in red and yellow, respectively. The red area is broad in the nasal hemifield retina of the right eyes from cases #1 through 3 and of the left eye of case #4. In contrast, the temporal hemifield retina is almost red in the left eyes of cases #1 through 3 and in the right eye of case #4

Discussion

The use of SD-OCT to determine a cpRNFL-TSNIT profile could detect the site-dependent thinning of cpRNFL in OTS, as previous reports by us and others have shown [2, 3]. However, these two reports used the earlier version of TD-OCT and only evaluated cpRNFL thickness. In this study, the difference in the presumed RNFL reduction rate in the temporal or nasal quadrants did not reach a statistical significance between eyes with temporal hemianopia and those with nasal hemianopia. This result may derive from the inaccuracy of cpRNFL measurements in the nasal and temporal quadrants based on the fixed circular scan [7]. The color-coded map may complement cpRNFL analyses as shown in Fig. 3.

GCC analysis provides information about the inner macular architecture. In this study, all cases exhibited marked changes in the GCC that were compatible with OTS but not changes in cpRNFL thickness. The cpRNFL in the superior and inferior parts of the optic nerve comprises retinal nerve fibers originating from both temporal and nasal hemiretinal areas. In contrast, GCC temporal to the fovea in the temporal hemiretina comprise strictly retinal ganglion cell elements that reside within the corresponding areas. Such enrichment in retinal ganglion cell components, as well as stringent retinotopical segregation may render the GCC superior to the cpRNFL in the detection of homonymous hemianoptic atrophy of the optic nerve due to OTS.

In conclusion, SD-OCT can detect the characteristic loss of nerve fibers secondary to OTS and might be a promising tool for the diagnosis of OTS.

Acknowledgement

Supported by Grant-in-Aid 22390324 (A.N., Y.Y. M.N.) and 23791983 (A.K.) for Scientific Research by the Ministry of Education, Culture, Sports, and Science and Technology of the Japanese Government, and the Suda Memorial Foundation (A.K.)

Copyright information

© Springer-Verlag 2012

Authors and Affiliations

  • Akiyasu Kanamori
    • 1
  • Makoto Nakamura
    • 1
  • Yuko Yamada
    • 1
  • Akira Negi
    • 1
  1. 1.Division of Ophthalmology, Department of SurgeryKobe University Graduate School of MedicineChuo-kuJapan

Personalised recommendations