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Umar Abdul Rehman, Shoaib Ugradar, Alan Le, Joseph Park, Christopher Lo, Daniel B Rootman; Quantification of Optic Nerve Length and Tortuosity in Thyroid Eye Disease. Invest. Ophthalmol. Vis. Sci. 2019;60(9):6213.
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© ARVO (1962-2015); The Authors (2016-present)
To objectively quantify the length and tortuosity of optic nerves (ONs) in patients with Thyroid eye disease (TED), in relation to the occurrence of dysthyroid optic neuropathy (DON).
All patients seen by two of the senior authors over a period of 12 years were screened for study entry. The primary outcome was the quantitative measurement of ON tortuosity and length in relation to the occurrence of dysthyroid optic neuropathy. Image analysis involved the creation of a 3D reconstruction of the ON from the anterior clinoid process (ACP) to the posterior globe using image analysis software. A centreline was created through the middle of the reconstruction and the length of the ON was calculated as the length of this centreline. Tortuosity was calculated by creating a ratio between the straight-line length of the ON and the actual length (centreline length).
Twenty cadaveric ONs were dissected to measure possible redundancy of the nerve within the sheath. The final sample included 50 patients who contributed 100 orbits. There were no differences in the Hertel exophthalmometry readings between patients with and without DON (p = 0.56). There was no significant relationship between the length (p = 0.39) and tortuosity (p = 0.82) of the ON and occurrence of DON. The cadaveric study revealed that the mean (SD) sheath length was 19.98 (2.1) and the mean nerve length was 19.94 (2.1).
There is no significant relationship between the length and tortuosity of the ON and development of DON in patients with TED. Chronic stretching of the ON does not appear to be a significant risk factor for the development of DON.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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