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Congenital tilted disc syndrome is characterized by inferior or inferonasal tilting of the optic disc, thinning of the choroid and retinal pigment epithelium of the inferior or inferonasal fundus, situs inversus of the retinal vessels, inferior or inferonasal crescent, myopic astigmatism and visual field defect. Previous studies suggested different retinal nerve fibre layer (RNFL) thickness profiles in congenital tilted disc syndrome compared with normal (Gurlu & Alymgyl 2005; Moschos et al. 2009). In this study, we investigated whether subjects with congenital tilted disc syndrome had different RNFL thickness profiles in optical coherence tomography (OCT) compared with normal subjects and whether it was associated with false positives in OCT.

Patients with congenital tilted disc syndrome were retrospectively recruited from the ophthalmology clinic of Seoul National University Boramae Hospital from 2007 to 2009. The diagnosis was based on the rotation of the disc upon its axis, inferior crescent, inferior chorioretinal hypoplasia and the oblique entrance of retinal vessels. Age, sex and refractive error-matched normal subjects were recruited as the normal group. Peripapillary fast RNFL scan of Stratus OCT was performed using a previously described technique (Jeoung et al. 2010). RNFL thickness was determined along a 3.4-mm-diameter circle around the optic disc with a spatial resolution of 256 points. All images should be well focused, have a centred circular ring around the optic disc and have a signal strength ≥6. The global average, quadrant and clock-hour RNFL thicknesses were compared between the congenital tilted disc group and the normal group. Superotemporal and inferotemporal peaks of the RNFL thickness were identified in the TSNIT (Temporal-superior-nasal-inferior-temporal) graph of the OCT (Fig. 1B). Angular locations of each peak point for the peripapillary scan circle were calculated as the temporal point beginning at 0–360°, clockwise in the right eye, and counterclockwise in the left. The ‘false positive’ means <5% level of normative database in clock-hour analysis or in TSNIT graph of Stratus OCT.

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Figure 1.  (A) Comparison of clock-hour retinal nerve fibre layer (RNFL) thickness profiles between the congenital tilted disc syndrome and normal groups. (t-test, *p < 0.001, †p < 0.05) B, C. Fundus photographs and optical coherence tomography (OCT) in subjects with congenital tilted disc syndrome. The fundus photographs show the tilted disc and thinning of retinal pigment epithelium in the inferior retina. The superotemporal and inferotemporal peak points (vertical black lines) were closely located towards temporal horizon in both cases. The clock-hour analysis of case (B) shows an abnormal finding of <5% level at 6 o’clock. The temporal-superior-nasal-inferior-temporal (TSNIT) curve of case (B) touches the yellow area of <5% level in the superior and inferior peripapillary RNFL. The TSNIT graph of case (C) also shows <5% level in the superior area.

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Sixteen eyes of 10 patients with congenital tilted disc syndrome and 40 eyes of 40 normal subjects were included in this study. The global RNFL average showed no significant difference. However, the RNFL in the temporal quadrant was thicker in the congenital tilted disc syndrome group than in the normal group (102.4 versus 85.5, p = 0.002). In contrast, the superior quadrant was thinner in the tilted disc group than in the normal group (124.1 versus 138.7, p = 0.003). The clock-hour thicknesses were significantly greater in the tilted disc group at the 9 and 10 o’clock sectors than in the normal group (p < 0.001); however, the tilted disc group had significantly thinner RNFL than did the normal group at the 12 and 1 o’clock sectors (p < 0.05) (Fig. 1A). There were significant differences in the superotemporal (p < 0.001) and inferotemporal (p = 0.033) peak points of RNFL thickness: both peaks were closer to the temporal horizon in the tilted disc group than in the normal group. The false positive rate in the clock-hour sector analysis with tilted disc group was significantly higher than it was in the normal group (31.3% versus 5.0%, p = 0.007). More frequent false positives were also found in the tilted disc group than in the normal group, with the analysis of the TSNIT graph (75% versus 7.5%, p < 0.001).

In summary, this study demonstrates that the topographic profiles of the RNFL thickness in the congenital tilted disc syndrome group are significantly different from those of the normal group. A different distribution of RNFL in congenital tilted disc syndrome could be a source of the high rate of false positives seen in the OCT RNFL analysis with a normative database.

Acknowledgement

  1. Top of page
  2. Acknowledgement
  3. References

This study was supported by a grant of the Korea Healthcare Technology R&D Project, Ministry of Health & Welfare, Republic of Korea (A100228).

References

  1. Top of page
  2. Acknowledgement
  3. References
  • Gurlu VP & Alymgyl ML (2005): Retinal nerve fiber analysis and tomography of the optic disc in eyes with tilted disc syndrome. Ophthalmic Surg Lasers Imaging 36: 494502.
  • Jeoung JW, Kim SH, Park KH, Kim TW & Kim DM (2010): Quantitative assessment of diffuse retinal nerve fiber layer atrophy using optical coherence tomography: diffuse atrophy imaging study. Ophthalmology 117: 19461952.
  • Moschos MM, Triglianos A, Rotsos T, Papadimitriou S, Margetis I, Minogiannis P & Moschos M (2009): Tilted disc syndrome: an OCT and mfERG study. Doc Ophthalmol 119: 2328.